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Rock Creek Park is a large urban park that bisects the Northwest quadrant of Washington, D.C. The park was created by an Act of Congress in 1890 and today is administered by the National Park Service. In addition to the park proper, the Rock Creek administrative unit of the National Park Service administers various other federally owned properties in the District of Columbia located to the north and west of the National Mall, including Meridian Hill Park on 16th Street, N.W., the Old Stone House in Georgetown, and certain of the Fort Circle Parks, a series of batteries and forts encircling the District of Columbia for its defense during the U.S. Civil War.

Rock Creek Park was established by an act of Congress signed into law by President Benjamin Harrison on September 27, 1890, following active advocacy by Charles C. Glover and other civic leaders and in the wake of the creation of the National Zoo the preceding year.

It was only the third national park established by the U.S., following Yellowstone in 1872 and Mackinac National Park in 1875. Sequoia was created at the same time, and Yosemite shortly thereafter. In 1933, Rock Creek Park became part of the newly formed National Capital Parks unit of the National Park Service.

The Rock Creek Park Act authorized the purchase of no more than 2,000 acres (810 ha) of land, extending north from Klingle Ford Bridge in the District of Columbia (approximately the northern limit of the National Zoo), to be "perpetually dedicated and set apart as a public park or pleasure ground for the benefit and enjoyment of the people of the United States". The Act also called for regulations to "provide for the preservation from injury or spoliation of all timber, animals, or curiosities within said park, and their retention in their natural condition, as nearly as possible". Rock Creek Park is the oldest natural urban park in the National Park System. Park construction began in 1897.

In 1913, Congress authorized creation of the Rock Creek and Potomac Parkway and extended the park along a narrow corridor from the zoo to the mouth of Rock Creek at the Potomac River. The parkway is a major traffic thoroughfare, especially along the portion south of the zoo. The park is patrolled by the United States Park Police.

Description

The main section of the park comprises 1754 acres (2.74 mi ², 7.10 km ²), along the Rock Creek Valley. Including the other green areas the park administers (Glover Archbold Park, Montrose Park, Dumbarton Oaks Park, Meridian Hill Park, Battery Kemble Park, Palisades Park, Whitehaven Park, etc.), it encompasses more than 2000 acres (3 mi ², 8 km ²).

The parklands follow the course of Rock Creek across the D.C.- Maryland border to connect with Rock Creek Stream Valley Park and Rock Creek Regional Park in Montgomery County. The Maryland parks are operated by the Maryland-National Capital Park and Planning Commission.

The Rock Creek Historic District was listed on the National Register of Historic Places on October 23, 1991.

Recreation facilities include a golf course; equestrian trails; sport venues, including a tennis stadium which hosts major professional events; a nature center and planetarium; the Carter Barron Amphitheatre, an outdoor concert venue; and picnic and playground facilities. Rock Creek Park also maintains cultural exhibits, including the Peirce Mill. Rock Creek is a popular venue for jogging, cycling, and inline skating, especially on the long, winding Beach Drive, portions of which are closed to vehicles on weekends.

A number of the city's outstanding bridges, such as the Lauzun's Legion, Dumbarton, Taft and the Duke Ellington bridges, span the creek and ravine.

Among the park's few monuments is a pink granite bench on Beach Drive south of the Peirce Mill, dedicated on November 7, 1936 by President Franklin Delano Roosevelt in memory of former French ambassador Jean Jules Jusserand. In 2014, it was named "best obscure memorial" by Washington City Paper.

Horse Center

Rock Creek Park Horse Center, founded in 1972, is located in the middle of the park near the Nature Center. The barn, run by Guest Services Inc, has 57 stalls, two outdoor rings, one indoor ring, and three bluestone turnout paddocks. The stable provides trail rides, pony rides, and lessons for the public, along with boarding for private horses. The stable primarily teaches English riding, with an emphasis on lower-level jumping and dressage.

The barn is also home to Rock Creek Riders, a therapeutic riding program for adults and children with special needs in the D.C. area. Past participants in the program include brain-injured veterans of the conflicts in Iraq and Afghanistan and people with autism, cerebral palsy, or attention deficit disorder. The program is volunteer-run and relies on donations and contributions for funding. Previously, Rock Creek Riders has worked with the United States Mounted Police, National Park Service, Wounded Warrior Project, and the Caisson Platoon Equine Assisted Programs to provide these therapeutic riding services.

The horse center's summer camps are popular with D.C. residents. The stable offers summer camp from 9-3 for children over eight, and a two-hour afternoon camp for children between five and eight years old. The stable also recently implemented a summer CIT training program for teenagers.

Peirce Mill

Peirce Mill is a water-powered grist mill in Rock Creek Park. There were at least eight mills along Rock Creek within what is now Washington, D.C., and many more farther upstream in Montgomery County, Maryland. Of those eight, only Peirce Mill is still standing.

It was built in the 1820s by Isaac Peirce, along with a house, barn, and other buildings. It was later owned by a son, Joshua Peirce, and a nephew Peirce Shoemaker. It became part of Rock Creek Park in 1892.

The mill was listed on the National Register in 1969 as Peirce Mill. It was repaired and re-opened October 15, 2011.

The Peirce Carriage Barn, adjacent to the mill, usually is open every day. The barn is the National Park Service point of contact. The barn was part of the Peirce estate built in 1810 and used as a tack room and carriage barn. The barn is now a mini-museum containing information on the milling process, the Peirce family estate and other mills along the Rock Creek Valley.

Rock Creek multi-use trails

A set of hiker/biker trails in the park serve both commuters and recreational users. The mainline trail extends for about 1.6 km (0.99 mi) from Broad Branch Road to the southern end of the Park where the trail continues several miles to Arlington Memorial Bridge and Hains Point. The northern trails, consist of a loop along Bingham, Oregon, Beach and Military Roads with spurs along Oregon to the Nature Center and Wise Road. In the Park, the mainline trail starts at the parking lot just west of the creek and south of Broad Branch. From there, it is co-located with a section of the Western Ridge Trail south past Pierce Mill to a trail bridge over the creek, where the two separate. After a short distance on the east side of the creek, it crosses back to the west side on Bluff Bridge. Dating back to 1934, it is the oldest part of the trail in the park, and the same age as the Devil's Chair and Saddle Club Bridges farther south. The trail remains on the west side until just south of Klingle Bridge where it crosses back to the east and leaves the park to enter the Zoo property.

The Park Service began to experiment with trails in August 1963 when mile-long Ross Drive was closed to cars from 6 am to noon on Sundays, but planning for a separate trail system didn't begin until 1965, when the federal "Trails for America" report identified a trail along Rock Creek as one of many trails for the D.C. area. That same year, the "Fort Park System, A Re-evaluation Study of Fort Drive, Washington, D.C." report suggested running the Circle Fort Trail through the park.

Planning for trails led to action. In January 1967, NPS announced weekend road closures in April over a 5-mile loop in the center of the park, made up of Beach, Ross, Ridge and Joyce and they announced a plan to build a trail from Military Road to the District boundary. That trail, the first hiker-biker trail in the park, was built in the summer of 1967. The crushed bluestone trail was constructed from the Nature Center, past Wise Road to a turnaround loop just southwest of Beach Drive and the D.C. boundary.

Over the next few months, NPS announced plans to add additional unpaved trails along Military Road from Oregon to Beach, along Wise to Fenwick Branch, beside Fenwick Branch to the District boundary and through Pinehurst Parkway Park (most of which were never constructed). In 1968, they built a second trail along Beach from Joyce to Bingham. By 1969, the two existing northern trails were connected with a trail along Bingham from Oregon to Beach. Later that year, NPS built the final section of the loop along Military between Oregon and Beach. By 1972, NPS had paved all of these trails except the section north of Wise to the DC Boundary. The section along Military Road was originally intended to serve as part of the Fort Circle Trail, passing by Fort DeRussy, but work on the Fort Circle Trail ended in the 1970s with only three parts, the one in Rock Creek, a section of the C&O Canal towpath and another from Fort Stanton to Fort Mahon, completed. Over time, the Rock Creek section ceased to be viewed as part of the Fort Circle Trail system. Between 1979 and 1981, the unpaved trail and turnaround loop north of Wise was abandoned.

Farther south, a trail along the creek was extended into the park in 1972. A trail along the Potomac built prior to 1967 was extended along the Rock Creek and Potomac Parkway in 1971 and then into the park in 1972. It was built on a bridle path that dated back to the early 20th century up to the Bluff Bridge, which was built in 1934. The section of bridle path used between P and Q streets was built in conjunction with the Pentagon, as that project needed dirt and the park service needed dirt removed. These first sections of trail were 4 to 8 feet wide with rough pavement, steep slopes, poor visibility and sharp curves. By 1977, the trail was extended to Broad Branch Road, crossing the creek at Bluff Bridge and twice on newly constructed "breakaway" bridges.

NPS and cyclists have long sought a way to close the gap on the north end of the park. After a 1973 proposal to extend the trail, NPS launched a study and announced a plan to do so in 1983, but quickly retracted it. In 1980, NPS, inspired by road closures in New York's Central Park, prepared an assessment of alternatives for a Bicycle Trail Study of the park that analyzed nine alternatives for completing the trail system, including construction of a new bike trail and alteration of the existing road network. After a period of public comment, NPS proposed expanding the weekend closure; constructing an additional 3.5 mi (5.6 km) of trail, designating Beach Drive north of Bingham a bicycle route and studying the suitability of a trail in that section. After years of additional study, public hearings and trial closures, NPS announced in February 1983 a plan to expand weekend closures and close Beach between Joyce and Broad Branch to automobile traffic. At first only one lane of Beach would be closed during rush hour, but after Metro's Red Line opened in Montgomery County in 1985, the section would be permanently closed. Six months later, under pressure from The American Automobile Association and the governments of D.C. and Montgomery County, the park service decided not to close the section of Beach. Instead, they decided to go ahead with the weekend closures and build a bicycle trail along a horse trail between Joyce and Broad Branch by 1986. But that trail was never built.

In 1982, the Park Service built two new bridges for the trail. One bridge across Rock Creek between Pennsylvania Avenue and K Street was built in conjunction with the roadway bridge reconstruction. Prior to the project, the trail used a narrow section of the existing bridge. That same year one of the two low-water breakaway bridges, just south of Pierce Mill, that was washed away by Hurricane David in 1979 was replaced with a high water bridge.

By 1990, biking on foot trails or bridle paths was no longer allowed. In 1991, the trail bridge beneath Porter Road, the other low-water breakaway bridge built in the 1970s, was replaced with a high-water bridge.

The prospect of completing a bike route across the park re-emerged in the 1990s when the Park was required to come up with a General Management Plan. In 1991, a loosely knit, cyclist-dominated group called "Auto-Free D.C." renewed the push to ban automobile traffic on Beach Drive. They suggested limited road closures to discourage commuters, but allow access to most locations in the park by car. When NPS failed to take up their suggestion, the group led a series of "rolling road block" protests which aimed to peaceably draw attention to the cause by disrupting rush hour traffic. Nonetheless, the protests led to some confrontations and arrests, and at one point the Military Road Bridge was graffitied with anti-automobile slogans. In 1996, NPS initiated a federally-mandated General Management Plan for the park. In June 1997, NPS laid out several management alternatives, one of which would improve and expand the paved multi-use trails and add a new trail along Wise, with the police substation converted to a visitor center and bicycle rental facility. Another alternative suggested that sections of Beach Drive be permanently closed and converted into a wide multi-use trail and that Wise Road, Sherrill Drive, Bingham Drive, Grant Road, and Blagden Avenue be converted to paved trails. Both of these alternatives were less popular than the status quo. An additional alternative created by the People's Alliance for Rock Creek (PARC), a group consisting of the Washington Area Bicyclists Association, the Sierra Club, Friends of the Earth and 18 other advocacy groups, suggested making Beach Drive auto-free north of Broad Branch as a means of completing the trail envisioned in 1965. In 2003, in an attempt to appease both groups, the Park Service proposed extending the weekend closures of Beach Drive to weekdays from 9:30 a.m. to 3:30 p.m. The proposal was one of several, but was the "preferred alternative." The plan had popular support, but no political support. Mayor Anthony Williams who had supported closure as a candidate, opposed it as mayor, citing the need to evacuate in a post-9/11 world. In May 2004, NPS proposed instead to only close the section from Joyce to Broad Branch, but again found opposition among politicians. So, in November 2005, the Park Service finalized their management plan which included no further road closures, the prospect of lowering speed limits and adding speed bumps, and improvements to the trail south of Broad Branch. However, speed limits were never reduced and no traffic calming was ever implemented.

The management plan completion cleared the way for the Park Service and DDOT to rebuild Beach Drive and the trail. Despite planning that started in 2005, work on the project didn't begin until September 22, 2016. The project rebuilt both Beach Drive and the trail. The trail section between Shoreham Drive and Broad Branch was widened to 8-10 ft (2.4-3.0 m), repaved and realigned; the Shoreham Drive crossing, reworked in 2006, was again improved; the traffic lanes in the Zoo Tunnel were narrowed to widen the trail through it by 3 ft (0.91 m); a new access to Harvard Street was built and 1,000 ft (300 m) of new trail was constructed between the Porter Street Bridge and Bluff Bridge. In conjunction with the project, the trail through the Klingle Road intersection was redesigned to connect to the new Klingle Valley Trail, which was built on the washed out section of Klingle Road and opened on June 24, 2017. The work on the trail south of Broad Branch was completed on January 8, 2018. Work on Beach Drive between Joyce and Bingham, which improved a short section of trail near the bridge over the creek was completed on September 27, 2019.

In 2018, DDOT announced plans to rehabilitate and expand the trail within both Rock Creek Park and outside of it. Within Rock Creek Park, they will rehabilitate a section between Klingle Road and Bluff Bridge and a section on the west side of the creek south of Broad Branch Road. They will also build a new trail along Piney Ridge Road from Beach Drive to Arkansas Avenue.

Though the 2005 D.C. bicycle plan only identified a need for "an improved bicycle connection" between Broad Branch and the Maryland Line, the 2013 MoveDC Multi-modal transportation plan includes a future trail on this section.

Sections of park roads have been subject to weekly closures to motor vehicles since the 1960s, though the times and locations changed. After the 1963 closure experiment, another was attempted in 1967 on Beach between Joyce and Broad Branch on Sunday mornings, but the response was not positive and it was discontinued. In 1970, NPS tried again, closing 2 mi (3.2 km) of Beach, and part of Morrow, every Sunday from 9 a.m. to 6 p.m., but was again discontinued due to a lack of use. But, in 1972, NPS tried for a fourth time, again closing Beach between Broad Branch and Joyce from 8 a.m. to 6 p.m. on Sundays and it became a permanent feature. On more than one occasion in the 1970s they experimented with Saturday closures in the summer, once to support a new bicycle concession near Carter Barron, which generated no negative response, but also little use. By 1980, they added the section from Tilden to Piney Branch Road and expanded the hours to 7 a.m. to 7 p.m. and in August 1981, they expanded the closure to Saturdays and holidays as an experiment. In July 1982, the weekend automobile ban was extended to the section of Beach from Picnic Grove 10 to Wise, and between West Beach and the D.C. boundary. In August 1983 they made the closures, between 7 a.m. and 7 p.m. every Saturday and Sunday, official policy as part of the scaled back 1983 Plan. In 1985, the hours were increased from 7 a.m. Saturday to 7 p.m. Sunday from early April to Veterans Day on upper Beach Drive and year-round between Joyce and Broad Branch roads. Finally, by 1998 the closures had expanded to include not just the three sections of Beach but also the entirety of Bingham and Sherril Drives within the park and last all year long.

Administration

As originally authorized by Congress, the park was governed by the Rock Creek Park Commission, comprising the Chief of Engineers of the Army, the engineer commissioner of the District of Columbia, and three presidential appointees. In 1933, the park, along with other National Capital Parks, was transferred to the jurisdiction of the National Park Service.

Rock Creek Park is also an administrative unit of the National Park Service responsible for administration of 99 properties in the District of Columbia north and west of the National Mall and Memorial Parks. The properties include various parks, parkways, buildings, circles, triangles, memorials, and statues and include:

Demographic significance

Although D.C.'s primary geographic metonyms for racial and class divisions are the city's quadrants ( i.e., Northwest, Southwest, Northeast, and Southeast), Rock Creek Park also separates prominent neighborhoods such as Georgetown, Cathedral Heights and Spring Valley from the rest of the city; hence, the designations WOTP (West of the Park) and EOTP (East of the Park) also serve this role.

Legislative history

Congressional authorizations:

Rock Creek Park - September 27, 1890

Meridian Hill Park - June 25, 1910

Montrose Park - March 2, 1911

Rock Creek and Potomac Parkway - March 4, 1913

Dumbarton Oaks Park - December 2, 1940

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Rock Creek Park is a large urban park that bisects the Northwest quadrant of Washington, D.C. The park was created by an Act of Congress in 1890 and today is administered by the National Park Service.

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Don’t worry, the green dye is non-toxic and biodegradable.

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9 Things to Do in Rock Creek Park | Washington DC

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Hike, run, picnic and more in the District’s urban oasis.

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You feel the ground suddenly shake, and nearby objects are trembling. An earthquake is happening.

Also called a temblor, an earthquake is caused by the movement of parts of the Earth's crust, its outermost layer. They happen millions of times a year, but most are so small people don't even feel them.

But powerful earthquakes can cause landslides, tsunamis, flooding, and other dangerous events. Most damage and deaths happen in places where a lot of people live, because the shaking causes windows to break, structures to collapse, fire to break out, and other dangers.

Learn more about these unpredictable Earth tremors-and what to do if one rattles near you.

How earthquakes develop

The action all starts thousands of miles below your feet.

Picture Earth as a hard-boiled egg: Earth's core is the yolk, and the mantle is the white part. The outer crust is the eggshell.

People live on the surface of the crust. Below the surface-but still within the crust-are tectonic plates. Like gigantic puzzle pieces, these huge slabs of rock encircle the Earth. The seven major plates are named for the regions they rest under: the African, Antarctic, Eurasian, Indo-Australian, North American, Pacific, and South American tectonic plates

Tectonic plates aren't connected but are close together. Where they meet along their edges is called a fault. When heat from the Earth's core creates currents in the crust, the tectonic plates can scrape, bump, or drag along each other. This is what causes an earthquake-and why the surface sometimes cracks like an eggshell.

How to measure earthquakes

About a half-million quakes rock the Earth every day. Usually the quake is too small, too far below the surface, or too deep in the seafloor to be felt. Some, however, are so powerful they can be felt thousands of miles away.

The spot on the surface just above where an earthquake starts is called the epicenter. Ripples called seismic waves travel out from the epicenter. This causes vibrations that people can feel, sometimes very far from the epicenter.

How far away people can feel an earthquake's vibrations depends on its size, or magnitude. Scientists base the magnitude on the strength and duration of the quake's seismic waves. The higher the number, the more powerful the earthquake: A magnitude 3 to 4.9 earthquake is considered minor; 5 to 6.9 is moderate to strong; 7 to 7.9 is major; and 8 or more is an extremely powerful temblor.

As the crust settles after an earthquake, another temblor called an aftershock can happen. Usually, aftershocks are not as powerful as the first quake but can still be very strong.

Geologists can't predict earthquakes. But they're working to change that with new research and technology.

Where earthquakes happen

Earthquakes occur along faults, the areas where tectonic plates meet. About 80 percent of earthquakes occur along the rim of the Pacific Ocean. Called the Ring of Fire because of the large number of volcanoes there, the area is a meeting point for many tectonic plates.

Earthquakes are also common in California because the region sits on top of the Pacific and North American tectonic plates. Temblors happen when these two plates grind against each other. About two-thirds of this movement happens along the San Andreas Fault.

Another major earthquake area in the United States is the New Madrid Seismic Zone, which affects Missouri, Arkansas, Tennessee, Kentucky, and Illinois.

How to survive an earthquake

Earthquakes can happen anytime or anywhere-even if you don't live near a fault. So it's a good idea to prepare.

* Talk with your family about the safest places in your home in case an earthquake hits. This could be under a sturdy table or next to an interior wall (one that is not connected to the outside).

* Look for heavy items that could fall or break during a quake, and move them to safer spots.

* Ask your parents to make sure you have an emergency kit containing things like first-aid supplies, a flashlight, a cell phone charger, and a battery-operated radio. Your family should also have enough food and water for at least 72 hours

DURING AN EARTHQUAKE: Most earthquakes last only 10 to 30 seconds, so it's important to get to a safe place fast. Remember three things during an earthquake: drop, cover, and hold on.

Drop: Get down on your hands and knees and crawl to your shelter.

Cover: Underneath a sturdy table, desk, or bed, cover your head and neck with your arms. If furniture isn't nearby, crouch down on your knees with your arms over your head and neck next to an interior wall. (Don't stand under a doorway-they can easily collapse.)

Hold on: If you're under a piece of furniture, hold on with one hand and move with the furniture if it starts sliding. Stay where you are until the shaking stops.

AFTER AN EARTHQUAKE: Once the earthquake ends, check for injuries. Listen to a radio for any warnings and instructions from official organizations like the United States Geological Survey. Be prepared for any aftershocks.

Text and images adapted from Everything Volcanoes and Earthquakes: Earthshaking photos, facts, and fun!

(Learn more about earthquakes at National Geographic.)

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Learn the science behind how earthquakes happen-and how you can stay safe if one hits.

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Earth Science, Geology

Image

Photograph by Koumlhn/ullstein bild courtesy of Getty Images

Igneous rocks form when magma (molten rock) cools and crystallizes, either at volcanoes on the surface of the Earth or while the melted rock is still inside the crust. All magma develops underground, in the lower crust or upper mantle, because of the intense heat there.

Igneous rocks can have many different compositions, depending on the magma they cool from. They can also look different based on their cooling conditions. For example, two rocks from identical magma can become either rhyolite or granite, depending on whether they cool quickly or slowly.

The two main categories of igneous rocks are extrusive and intrusive. Extrusive rocks are formed on the surface of the Earth from lava, which is magma that has emerged from underground. Intrusive rocks are formed from magma that cools and solidifies within the crust of the planet.

When lava comes out of a volcano and solidifies into extrusive igneous rock, also called volcanic, the rock cools very quickly. Crystals inside solid volcanic rocks are small because they do not have much time to form until the rock cools all the way, which stops the crystal growth. These fine-grained rocks are known as aphanitic-from a Greek word meaning "invisible." They are given this name because the crystals that form within them are so small that they can be seen only with a microscope. If lava cools almost instantly, the rocks that form are glassy with no individual crystals, like obsidian. There are many other kinds of extrusive igneous rocks. For example, Pele's hair is long, extremely thin strands of volcanic glass, while pahoehoe is smooth lava that forms shiny, rounded piles.

Intrusive rocks, also called plutonic rocks, cool slowly without ever reaching the surface. They have large crystals that are usually visible without a microscope. This surface is known as a phaneritic texture. Perhaps the best-known phaneritic rock is granite. One extreme type of phaneritic rock is called pegmatite, found often in the U.S. state of Maine. Pegmatite can have a huge variety of crystal shapes and sizes, including some larger than a human hand.

National Geographic Society

July 15, 2022

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Earth Science, Geology Image Photograph by Koumlhn/ullstein bild courtesy of Getty Images Igneous rocks form when magma (molten rock) cools and crystallizes, either at volcanoes on the surface of the Earth or while the melted rock is still inside the crust. All magma develops underground, in the lower crust or upper mantle, because of the intense heat there.

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Erosion is a process where natural forces like water, wind, ice, and gravity wear away rocks and soil. It is a geological process, and part of the rock cycle. Erosion occurs at the Earth's surface, and has no effect on the Earth's mantle and core.

Most of the energy that makes erosion happen is provided by the Sun. The Sun's energy causes the movement of water and ice in the water cycle and the movement of air to create wind.

Erosion can cause problems that affect humans. Soil erosion, for example, can create problems for farmers. Soil erosion can remove soil, leaving a thin layer or rocky soil behind. Erosion can also cause problems for humans by removing rocks or soil that support buildings.

Erosion by water

Temperature changes cause pieces of rock to flake away from the surface. Also, the acid in rainwater dissolves rocks containing calcium carbonate. These processes are called weathering.

Water erosion happens when water moves the pieces of rock or soil downhill. Waves also carry away small pieces of material. A wave can wash up onto the surface of rock or soil and then carry away pieces of material as it flows back into the ocean or lake.

The size of earth materials that can be moved by water depends on how fast the water is moving. A fast-flowing stream can carry large rocks while a slow moving stream might only be able to carry very small things like clay. Canyons, like the Grand Canyon, are among the most obvious features made by erosion. Where a river meets the sea, it drops the solids, sometimes making a river delta.

Tropical rivers

Large tropical rivers like the Paraná, Indus, Brahmaputra, Ganges, Zambezi, Mississippi and the Amazon carry huge amounts of sediment down to the sea. The Nile, perhaps the world's longest river, carries much less sediment than the others because, part of the way, it runs through less fertile regions than the other great rivers.

The Amazon has by far the largest waterflow, with an average discharge greater than the next seven largest rivers combined. It has the largest drainage basin in the world, about 7,050,000 square kilometres (2,720,000 sq mi). The Amazon accounts for about one-fifth of the world's total river flow.

The sediment discharged by the gigantic mouth of the Amazon stains the sea brown for hundreds of miles out to sea.

Erosion by ice

Ice erosion happens when a glacier moves downhill. As the ice of the glacier moves downhill, it pushes and pulls earth materials along with it. Glaciers can move very large rocks. Ice erosion can happen in another way. Cold weather causes water inside tiny cracks in rocks to freeze. As it freezes, the ice gets bigger, and pushes hard against the rock. This can break the rock.

Erosion by wind

Wind erosion occurs when wind moves pieces of earth materials. Wind erosion is one of the weakest kinds of erosion. Small pieces of earth material can be rolled along the ground surface by wind. Very small pieces can be picked up and carried by the wind. Sometimes, wind can carry small pieces of earth materials over large distances. Some sediment from the Sahara Desert is carried across the Atlantic Ocean by wind.

One of the most famous examples of wind erosion occurred in the Dust Bowl, when wind erosion severely damaged farming communities.

Erosion by gravity

Gravity erosion is the simplest kind of erosion. Gravity simply pulls loose earth materials downhill. Landslides are dramatic examples of gravity erosion.

Erosion and tectonics

Tectonic effects on erosion has long been recognized. For example, rivers form as a result of tectonic uplift (as Himalayas and Tibetan Plateau). All of the Earth's mountain ranges were created by the upward movement of the land by changes beneath the Earth's surface. When the ground rises the whole weather system can also be changed including local sea levels, wind strength and direction, rainfall and more.

The Earth's landscape is a product of two factors. Tectonics builds up height by surface and rock uplift, and climate controls the erosion. Erosion wears away upland areas over time. The interaction of these processes can form, modify, or destroy features of the Earth's surface.

Images for kids

Wave cut platform caused by erosion of cliffs by the sea, at Southerndown in South Wales

In Spanish: Erosión para niños

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Earthquakes: Figuring out how they start

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Earthquakes: Figuring out how they start

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The Earth was formed about 4.6 billion years ago. The planet was so hot that the entire Earth was molten or liquid. As the Earth cooled, the lightest materials floated to the top and the heaviest materials sank to the center. The outer part of the Earth, the crust, consists of the lightest rock.

The lightest rocks form the continents, which are made mostly of the rock granite. Most of the granite on the continents has, over millions of years, been broken down, transported, and deposited into sedimentary rock. These layers of sedimentary rock vary from 8-9 miles thick to nothing in some areas like the Canadian Shield of North America. The Canadian Shield has huge outcroppings of granite right on the surface. Under the thick layers of sedimentary rock lies the denser granite.

The granitic continents ride on a much denser rock called basalt. These basalts form the bottom of our continents and the bottoms of our great oceans. This layer of rock extends down to 40 miles from the surface of the earth.

The crust is very thin in comparison to the other layers of the earth. The crust is only 3 miles thick under the oceans and about 40 miles thick under the highest mountain chains. The layer of the earth under the crust is called the mantle. It is over 1800 miles thick!! The crust and the upper level of the mantle form a layer of the earth that moves very slowly (1-4 inches per year). This layer that moves and causes earthquakes and volcanoes is called the Lithosphere.

Rocks are made of two or more different minerals that have been:

1. cemented together, or

2. squeezed and heated together, or

3. melted and cooled together.

Rocks make up the majority of the Earth's crust. One of the most common rock is granite. The four minerals that make up granite are feldspar, quartz, mica, and hornblende. Granite was formed when magma cooled slowly forming crystals of the four minerals that make up the rock granite.

Look at the photo above of granite. Notice the different mineral crystals that make up the rock, granite.

Most of the Earth's surface rocks are covered by soil or clay. Soil contains very small crushed pieces of rock and organic (plant and animal remains) material. Plants such as grass and trees grow in this region of the crust.

The photo above shows a recent eruption of ash that has covered and burned an area of dense vegetation in Hawaii. The lava has cooled and is now a volcanic rock called basalt. The weathering process will break the basalt down into small, finer pieces of rock called soil. This process can take a few years or thousands of years to produce soil fine enough for plants to grow well in. The soil will become fertile when bacteria decomposes plant and animal material adding nutrients for living plants.

Rocks are produced in a variety of ways and have been cycled in some area many times. This cycling of the rocks is called the rock cycle.

The rock cycle shows how the earth's rocks are changed again and again. The rocks can be changed at times to another type of rock. The rock cycle can begin anywhere in the cycle. Lets start with igneous rocks. Igneous rocks start as magma. The magma (molten rock under the surface) and lava (molten rock on the surface) hardens into igneous rock. The igneous rock then breaks apart over time through the process of weathering. These bits of broken rock are washed away by rains and deposited in a river. These pieces of igneous rocks are cemented together with other bits of rock and form a sedimentary rock called conglomerate. Over time sedimentary rocks can be buried by earthquakes or other geologic processes. Being buried deep under the surface in areas of high temperatures and pressures or coming in contact with magma can cause these sedimentary rocks to change to metamorphic rocks.

Diagram 1 shows layers of rocks around and under a volcano. The white blocks are a sedimentary rock called limestone. Limestone forms on the bottom of the ocean over many, many years. The fish and shelled sea animals decompose and their bones and shells break down into a chemical called calcium carbonate (CaCO3). This is the cementing agent that binds the sediments that fall to the sea floor into the rock called limestone. Magma has pushed its way to the surface and is now coming into contact with the surrounding rock layers.

Diagram 2 shows the limestone being heated by the magma and changing to the metamorphic rock called marble (Yellow). Marble is a beautiful rock that is used by humans as building material and for decorative uses as in sink tops or monuments. Artists have sculpted marble into some of the greatest works of art in the world.

The three main rock classifications are Igneous, Sedimentary, and Metamorphic. Rocks are classified into these groups by the way they were formed.

Rocks that formed from magma are called igneous rocks. Igneous comes from the Latin word ignis which means "fire". Rocks that are formed from heat and pressure are called metamorphic rocks. Rocks that are formed from the cementing together of small pieces of rocks or shells are called sedimentary rocks. We will discuss these three types of rocks more in depth later in this chapter.

This map of the United States and parts of Mexico and Canada shows what type of rock makes up the surface of these regions. The majority of the surface rocks on the North American continent are sedimentary. The mountainous regions of the west and southwest are made of igneous rocks. The Appalachian Mountain region of the eastern U.S. and most of eastern Canada are made of metamorphic rocks.

Granite is an igneous rock that is composed of four minerals. These minerals are quartz, feldspar, mica, and usually hornblende. Granite forms as magma cools far under the earth's surface. Because it hardens deep underground it cools very slowly. This allows crystals of the four minerals to grow large enough to be easily seen by the naked eye. Look at the photo of granite above, notice the different crystals in the rock.

Granite is an excellent material for building bridges and buildings because it can withstand thousands of pounds of pressure. It is also used for monuments because it weathers slowly. Engravings in the granite can be read for hundreds of years, making the rock more valuable.

Granite is quarried in many places in the world including the United States. The state of New Hampshire has the nickname "Granite State" because of the amount of granite in the mountains of that beautiful state. The Canadian Shield of North America contains huge outcroppings (surface rocks) of granite.

Milky quartz is a common mineral that is found in many different types of rocks. The chemical formula is Silicon oxide (SiO2). One type of quartz is easily identified by its hexagonal crystals, but quartz can also be found in a large mass. Quartz can be broken or weathered into the tiny pieces we know as sand. Quartz is a very hard mineral and in fact is the hardest of the common minerals. Quartz is number seven on the Mohs hardness scale. Quartz is also chemically stable, which means that it weathers very slowly.

Quartz can be colored yellow, milky white, rose, smoky (brown or black), and the best known of the colored crystals amethyst, which is purple. Impurities in the rock at the time of formation causes the quartz crystal to have these different colors.

Quartz is used by humans in producing optical instruments and electical devices. It is also used to make sandpaper and grinding tools.

Feldspar is the most abundant mineral in rocks that are located at or near the earth's surface. Feldspar can have a glassy white, blue, green, or red crystals. All feldspars contain silica and aluminum.

When feldspars are exposed to the atmosphere they break down or weather easily. When they are broken down, feldspar forms other minerals, many of which are clay minerals. Feldspars also contain potassium which is a major nutrient for plant growth.

The clays formed by weathered feldspar are used by pottery manufacturing plants. Kaolinite is the highest quality of the feldspar clays used by potters.

Feldspar is number 6 on the Mohs hardness scale.

Hornblende is a mineral that contains magnesium, iron, silica and aluminum. Hornblende is black, brown and green in color. It occurs in crystals of many igneous rocks.

Mica is a mineral that can be split into very thin sheets. These sheets can be so thin that 1000 can be layered into mica 1 inch high. Mica can be clear, black, green, red, yellow, and brown. Clear mica is called Muscovite because it is found near Moscow, Russia and was used as window glass in the Muscovite's homes. Muscovite contains water which helps to make it clear. Biotite mica is dark green to black in color because it contains iron, magnesium.

Mica is mined in Brazil, India, many parts of Africa, Canada, and the United States. It is used in the manufacturing of electronic and electrical devices.

Write the answers to the following questions in complete sentences on a piece of paper.

In your own words write a definition for rock.

What is soil composed of?

Describe in your own words how the rock cycle works.

Name the four minerals that granite is made from and a human use for each of the four minerals.

Name the three classifications for rocks.

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The Earth was formed about 4.6 billion years ago. The planet was so hot that the entire Earth was molten or liquid. As the Earth cooled, the lightest materials floated to the top and the heaviest materials sank to the center. The outer part of the Earth, the crust, consists of the lightest rock.

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Earthquakes: How do scientists study earthquakes?

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Earthquakes: How do scientists study earthquakes?

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Previewing Earthquakes - Tremors from Below.pdf

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The Four Layers

The Earth is composed of four different layers. Many geologists believe that as the Earth cooled the heavier, denser materials sank to the center and the lighter materials rose to the top. Because of this, the crust is made of the lightest materials (rock- basalts and granites) and the core consists of heavy metals (nickel and iron).

The crust is the layer that you live on, and it is the most widely studied and understood. The mantle is much hotter and has the ability to flow. The Outer and Inner Cores are hotter still with pressures so great that you would be squeezed into a ball smaller than a marble if you were able to go to the center of the Earth!!!!!!

The Crust

The Earth's Crust is like the skin of an apple. It is very thin in comparison to the other three layers. The crust is only about 3-5 miles (8 kilometers) thick under the oceans(oceanic crust) and about 25 miles (32 kilometers) thick under the continents (continental crust). The temperatures of the crust vary from air temperature on top to about 1600 degrees Fahrenheit (870 degrees Celcius) in the deepest parts of the crust. You can bake a loaf of bread in your oven at 350 degrees Fahrenheit , at 1600 degrees F. rocks begin to melt.

The crust of the Earth is broken into many pieces called plates. The plates "float" on the soft, plastic mantle which is located below the crust. These plates usually move along smoothly but sometimes they stick and build up pressure. The pressure builds and the rock bends until it snaps. When this occurs an Earthquake is the result!

Notice how thin the crust of the Earth is in comparison to the other layers. The seven continents and ocean plates basically float across the mantle which is composed of much hotter and denser material.

The crust is composed of two basic rock types granite and basalt. The continental crust is composed mostly of granite. The oceanic crust consists of a volcanic lava rock called basalt.

Basaltic rocks of the ocean plates are much denser and heavier than the granitic rock of the continental plates. Because of this the continents ride on the denser oceanic plates. The crust and the upper layer of the mantle together make up a zone of rigid, brittle rock called the Lithosphere. The layer below the rigid lithosphere is a zone of asphalt-like consistancy called the Asthenosphere. The asthenosphere is the part of the mantle that flows and moves the plates of the Earth.

The Mantle

The mantle is the layer located directly under the sima. It is the largest layer of the Earth, 1800 miles thick. The mantle is composed of very hot, dense rock. This layer of rock even flows like asphalt under a heavy weight. This flow is due to great temperature differences from the bottom to the top of the mantle. The movement of the mantle is the reason that the plates of the Earth move! The temperature of the mantle varies from 1600 degrees Fahrenheit at the top to about 4000 degrees Fahrenheit near the bottom!

Convection Currents

The mantle is made of much denser, thicker material, because of this the plates "float" on it like oil floats on water.

Many geologists believe that the mantle "flows" because of convection currents. Convection currents are caused by the very hot material at the deepest part of the mantle rising, then cooling, sinking again and then heating, rising and repeating the cycle over and over. The next time you heat anything like soup or pudding in a pan you can watch the convection currents move in the liquid. When the convection currents flow in the mantle they also move the crust. The crust gets a free ride with these currents. A conveyor belt in a factory moves boxes like the convection currents in the mantle moves the plates of the Earth.

Outer Core

The core of the Earth is like a ball of very hot metals. (4000 degrees F. to 9000 degrees F.) The outer core is so hot that the metals in it are all in the liquid state. The outer core is located about 1800 milesbeneath the crust and is about 1400 miles thick. The outer core is composed of the melted metals nickel and iron.

Inner Core

The inner core of the Earth has temperatures and pressures so great that the metals are squeezed together and are not able to move about like a liquid, but are forced to vibrate in place as a solid. The inner core begins about 4000 miles beneath the crust and is about 800 miles thick. The temperatures may reach 9000 dgrees F. and the pressures are 45,000,000 pounds per square inch. This is 3,000,000 times the air pressure on you at sea level!!!

Answer the following questions on a sheet of paper with your partner. If you need to look back to find the answers use the page titles located directly under the questions to help you. When you finish the questions click on the Earth icon to return the program to the beginning.

Name the four layers of the Earth in order from the outside to the center of the Earth.

What are the two main metals that make up the outer and inner core?

Describe in your own words how the Earth's layers were formed. "The Four Layers" will help you.

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The Four Layers The Earth is composed of four different layers. Many geologists believe that as the Earth cooled the heavier, denser materials sank to the center and the lighter materials rose to the top. Because of this, the crust is made of the lightest materials (rock- basalts and granites) and the core consists of heavy metals (nickel and iron).

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The secrets buried inside our planet are revealed by recording and studying things called seismic waves. Caused by things like earthquakes, explosions and the movement of our oceans, there are two types of seismic wave - a shear wave, which won't travel through liquid; and a pressure wave, which moves through both liquid and solids. These waves show that the Earth is made from five layers: the inner and outer core, the lower and upper mantle, and the crust.

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The Earth's inner core is a huge metal ball, 2,500km wide. Made mainly of iron, the temperature of the ball is 5,000°C to 6,000°C - that's up to 6,000 times hotter than our atmosphere and scorching enough to make metal melt! The metal at the inner core stays solid because of the incredible pressure surrounding it.

Temperature: 4,000°C - 6,000°C
State: Liquid
Composition: iron, nickel, sulphur and oxygen

This liquid layer of iron and nickel is 5,150km deep. The outer core flows around the centre of the Earth, and the movement of the metals creates our planet's magnetic field.

Lower Mantle

The lower mantle is found between 670km and 2,890km below the surface, and is made from solid rock. The rock is hot enough to melt, but is solid because of the pressure pushing down on it.

Upper Mantle

Temperature: 1,400°C - 3,000°C
State: liquid / solid
Composition: iron, oxygen, silicon, magnesium and aluminium

This layer is up to 670km below the Earth's surface. The lower part of the upper mantle is made from both solid and melted rock (liquid), while the rock in the upper region is stiffer, because it's cooler.

Temperature: Around 22°C
State: Solid
Composition: Oceanic crust made up of iron, oxygen, silicon, magnesium and aluminium.
Continental crust made up of granite, sedimentary rocks and metamorphic rocks.

The Earth's surface is covered by its thinnest layer, the crust. Land is made of continental crust, which is 8km to 70km thick and made mostly from a rock called granite. The layer beneath the ocean bed is made of oceanic crust, which is about 8km thick and made mainly from a rock called basalt.

By studying rocks and meteorites (rocks from space), scientists believe the Earth is about 4.5 billion years old!

Illustration: Getty Images UK

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Structure of the Earth! - National Geographic Kids

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Learn all about the structure of the Earth here at National Geographic Kids! Join us as we explore the different layers - the crust, upper mantle, lower mantle, outer core and inner core...

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Earth's Layer | Ready Jet Go! | PBS LearningMedia

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What does an ordinary cake and the planet Earth have in common? Both are made up of layers! In this clip from Ready Jet Go!, Jet learns about Earth's four distinct layers and their characteristics: the crust, the mantle, the outer core, and the inner core.

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Kids learn about the science of the composition of the Earth. Different layers and what they do.

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Geology Kitchen #8 - Layers of the Earth

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Earth Science, Geology

Image

Photo courtesy of Alamy Stock Photo

Sedimentary rocks are formed on or near the Earth's surface, in contrast to metamorphic and igneous rocks, which are formed deep within the Earth. The most important geological processes that lead to the creation of sedimentary rocks are erosion, weathering, dissolution, precipitation, and lithification.

Erosion and weathering include the effects of wind and rain, which slowly break down large rocks into smaller ones. Erosion and weathering transform boulders and even mountains into sediments, such as sand or mud. Dissolution is a form of weathering-chemical weathering. With this process, water that is slightly acidic slowly wears away stone. These three processes create the raw materials for new, sedimentary rocks.

Precipitation and lithification are processes that build new rocks or minerals. Precipitation is the formation of rocks and minerals from chemicals that precipitate from water. For example, as a lake dries up over many thousands of years, it leaves behind mineral deposits; this is what happened in California's Death Valley. Finally, lithification is the process by which clay, sand, and other sediments on the bottom of the ocean or other bodies of water are slowly compacted into rocks from the weight of overlying sediments.

Sedimentary rocks can be organized into two categories. The first is detrital rock, which comes from the erosion and accumulation of rock fragments, sediment, or other materials-categorized in total as detritus, or debris. The other is chemical rock, produced from the dissolution and precipitation of minerals.

Detritus can be either organic or inorganic. Organic detrital rocks form when parts of plants and animals decay in the ground, leaving behind biological material that is compressed and becomes rock. Coal is a sedimentary rock formed over millions of years from compressed plants. Inorganic detrital rocks, on the other hand, are formed from broken up pieces of other rocks, not from living things. These rocks are often called clastic sedimentary rocks. One of the best-known clastic sedimentary rocks is sandstone. Sandstone is formed from layers of sandy sediment that is compacted and lithified.

Chemical sedimentary rocks can be found in many places, from the ocean to deserts to caves. For instance, most limestone forms at the bottom of the ocean from the precipitation of calcium carbonate and the remains of marine animals with shells. If limestone is found on land, it can be assumed that the area used to be under water. Cave formations are also sedimentary rocks, but they are produced very differently. Stalagmites and stalactites form when water passes through bedrock and picks up calcium and carbonate ions. When the chemical-rich water makes its way into a cave, the water evaporates and leaves behind calcium carbonate on the ceiling, forming a stalactite, or on the floor of the cave, creating a stalagmite.

National Geographic Society

July 15, 2022

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Earth Science, Geology Image Photo courtesy of Alamy Stock Photo Sedimentary rocks are formed on or near the Earth's surface, in contrast to metamorphic and igneous rocks, which are formed deep within the Earth. The most important geological processes that lead to the creation of sedimentary rocks are erosion, weathering, dissolution, precipitation, and lithification.

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The term "metamorphosis" is most often used in reference to the process of a caterpillar changing into a butterfly. However, the word "metamorphosis" is a broad term that indicates a change from one thing to another. Even rocks, a seemingly constant substance, can change into a new type of rock. Rocks that undergo a change to form a new rock are referred to as metamorphic rocks.

In the rock cycle, there are three different types of rocks: sedimentary, igneous, and metamorphic. Sedimentary and igneous rocks began as something other than rock. Sedimentary rocks were originally sediments, which were compacted under high pressure. Igneous rocks formed when liquid magma or lava-magma that has emerged onto the surface of the Earth-cooled and hardened. A metamorphic rock, on the other hand, began as a rock-either a sedimentary, igneous, or even a different sort of metamorphic rock. Then, due to various conditions within the Earth, the existing rock was changed into a new kind of metamorphic rock.

The conditions required to form a metamorphic rock are very specific. The existing rock must be exposed to high heat, high pressure, or to a hot, mineral-rich fluid. Usually, all three of these circumstances are met. These conditions are most often found either deep in Earth's crust or at plate boundaries where tectonic plates collide. In order to create metamorphic rock, it is vital that the existing rock remain solid and not melt. If there is too much heat or pressure, the rock will melt and become magma. This will result in the formation of an igneous rock, not a metamorphic rock.

Consider how granite changes form. Granite is an igneous rock that forms when magma cools relatively slowly underground. It is usually composed primarily of the minerals quartz, feldspar, and mica. When granite is subjected to intense heat and pressure, it changes into a metamorphic rock called gneiss.

Slate is another common metamorphic rock that forms from shale. Limestone, a sedimentary rock, will change into the metamorphic rock marble if the right conditions are met.

Although metamorphic rocks typically form deep in the planet's crust, they are often exposed on the surface of the Earth. This happens due to geologic uplift and the erosion of the rock and soil above them. At the surface, metamorphic rocks will be exposed to weathering processes and may break down into sediment. These sediments could then be compressed to form sedimentary rocks, which would start the entire cycle anew.

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Metamorphic Rocks | National Geographic Society

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The term "metamorphosis" is most often used in reference to the process of a caterpillar changing into a butterfly. However, the word "metamorphosis" is a broad term that indicates a change from one thing to another. Even rocks, a seemingly constant substance, can change into a new type of rock.

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There are three types of rock: igneous, sedimentary, and metamorphic. These names describe how each type of rock was formed.

Igneous rock is hardened magma. Magma may escape through cracks in Earth's crust. It may also come to Earth's surface when a volcano erupts. As the escaped magma cools, it hardens into solid rock. Granite and basalt are examples of igneous rock.

Sedimentary rock may form from pieces of other rock. In a process called erosion, wind and water slowly break rock into tiny pieces. Water washes the pieces into rivers. They settle along the river bottom in soft, loose layers called sediment. Over millions of years the sediment builds up, hardens, and becomes solid rock. Sandstone is a sedimentary rock that forms in this way. Sedimentary rock also may form from the remains of dead animals or plants. Limestone is a sedimentary rock that is made up of the shells and stony skeletons of certain kinds of living things.

Metamorphic rock forms from old igneous or sedimentary rock. Several forces can change old rock into new metamorphic rock. Great heat and pressure inside Earth's crust can shape old rock into metamorphic rock. Water can dissolve minerals in old rock or carry new minerals into it to form metamorphic rock. The heat of magma can also change old rock into metamorphic rock. Marble and slate are examples of metamorphic rock.

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There are three types of rock: igneous, sedimentary, and metamorphic. These names describe how each type of rock was formed. Igneous rock is hardened magma. Magma may escape through cracks in Earth's crust. It may also come to Earth's surface when a volcano erupts. As the escaped magma cools, it hardens into solid rock.

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Kids learn about the Earth science subject of plate tectonics including major and minor plates, convergent, divergent, and transform boundaries.

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Volcanic activity is the most powerful force in nature. Some volcanic eruptions are much more powerful than the largest nuclear explosion. Volcanoes have killed thousands of people and have created some of the most frightening events in human history.

Volcanoes have been the basis for myths and legends the world over.

Volcanoes are also responsible for much of the land we live on, 90% of all the continents and ocean basins are the product of volcanism. The air we breathe, and the water we drink have been produced by millions of years of eruptions of steam and other gases.

The volcanic mountain above is Mount Adams which is located in the Cascade Range of Washington.

The word volcano is derived from the name of the ancient Roman island of Vulcano which lies off the southwest coast of Italy. The Romans believed that Vulcan, the god of fire and the maker of weapons, used the volcano on that island to forge his weapons.

Volcanoes are not alive but scientists use human terms to talk about volcanoes, such as active, alive, dormant, resting, sleeping, extinct, dead, lifetime, and restless.

The island in the middle of the picture is Vulcano. The island was formed by Vulcanian eruptions, which are eruptions of hot gas and steam followed by ejections of thick and pasty lava.

The term Volcano has two definitions;

1. An opening in the crust of the Earth in which molten rock called magma and gases can escape to the surface.

2. The mountain that is formed from volcanic eruptions.

This is a photo of the volcano Paricutin (Pear-A-Koo-Teen). Paricutin's cone formed from nine years of almost constant eruptions. Red hot cinders exploded from the main vent and landed near it building the cone higher and higher. This type of cone is called a cinder cone. You will learn more about the types of volcanic cones in the eighth lesson, "Volcanic Cones and Eruptions".

Volcanoes actually build themselves into a mountain with repeated eruptions. In 1943 a farmer in Mexico noticed that some cracks (fissures) in his corn field were growing wider and wider. The next day his field was engulfed by a growing volcanic cone (Light Green). During the week the cone grew 500 feet taller (Dark Green). Within a year (Dark Gray) Paricutin was over 1200 feet higher than the surrounding landscape. During the next eight years the volcano did not grow much taller but the cone's base grew wider and wider (Light gray). Paricutin stopped erupting in 1952 almost as fast as it started. The mountain has been silent since.

Volcanoes can build themselves into high mountains one day and in the case of Mt. St. Helens erupt violently blowing their top off the next day. Mt. St. Helens lost over 1300 feet of its summit during the eruption and simultaneous landslide of 1980.

Volcanoes are classified as active, dormant, and extinct. Active volcanoes are either currently erupting or have erupted in recorded history. There are over 500 volcanoes on Earth that fit this category today. Dormant or resting volcanoes are not currently erupting but are considered likely to do so. Mt. St. Helens had been dormant for one hundred twenty-three years before it erupted in 1980. Extinct or dead volcanoes have not erupted in recorded history and are not expected to erupt again.

The photo above is of beautiful Mt. St. Helens before it erupted on May 18, 1980. Mt. St. Helens was one of the most beautifully symetrical stratovolcanoes in the world. It was called "the Fuji of the west". Mount Fuji, in Japan, is the most photographed mountain in the world. The next card will show you what this mountain looked like shortly after the eruption. The lake in the foreground changed. The lake's level is now 150 feet higher because the landslide and eruption filled the bottom of the lake with rock, soil, and pyroclasts.

This is Mt. St. Helens four months after the eruption. Notice the loss of over 1300 feet of the summit. Also notice the total devastation of the beautiful forests and how Spirit Lake rose. Spirit Lake's surface was completely filled with trees that were blasted into the lake by the force of the eruption. The lake is now much more shallow, wider, and longer than before the eruption. Huge trees still float across the lake today.

The eruption left a crater over a mile wide and over 2000 feet deep. The mountain is still active today spewing small whisps of steam. A lava dome is growing in the bottom of the huge crater.

The lava is so A lava dome is a steep mass of very thick and pasty lava that is pushed up from the main vent. viscous (thick and pasty) that it does not flow but slowly rises higher with each movement of magma in the conduit. Think of toothpaste that is slowly squeezed and then stopped and then squeezed again from the tube. This is how the lava dome in Mt. St. Helen's was formed.

The dome's exterior surface is very rough with chunks of lava that were formed from small eruptions that broke the cooled and hardened surface into blocks.

The dome slowly "grew" larger and larger over a seven year period. An earlier dome started to form one month after the famous eruption when very thick lava (dacitic lava) rose into the crater from the magma chamber below. This dome was destroyed by an explosive eruption just a month later.

The large dome that is very visible today is over 900 feet tall (taller than an 80 story building) and over 3000 feet wide (10 football fields). As large as the lava dome is, it is still dwarfed by the huge crater that was the result of the 1980 eruption. Steamy whisps of steam are still visible from the dome telling us that the volcano's magma is filling the conduit, making the volcano still active today.

There are three ways that volcanoes form. Subduction Zone volcanoes form at the boundaries of two plates, one overriding the other. Subduction zone volcanoes are the most violent and destructive of the volcanic types. Mt. St. Helens, Mt. Pinatubo, Krakatoa, and Mt. Vesuvius are all famous explosive subduction zone volcanoes. Mid-ocean rift volcanoes form where two oceanic plates are spreading apart. There are more rift zone volcanoes than any other type.

These mid-ocean or rift zone volcanoes are the world's longest continuous mountain chain. This mountain chain encircles the entire Earth. It is more than 40,000 miles long.

The third way that volcanoes form occurs at a Hot Spot. Hot spots are usually found under oceanic crust, but can be located under continental crust. You will learn more about Hot Spot volcanoes in the lesson "Hot Spots-Yellowstone and Hawaii".

The diagram above shows the three ways that volcanoes form.

Predicting exactly when a volcano will erupt is next to impossible. Today geologists are becoming much more accurate in making the public aware that a volcano is showing signs that it may erupt in the near future.

In the months before Mt. St. Helens erupted geologists knew the mountain was getting restless. A magnitude 4.1 earthquake was recorded on March 20 (about 2 months before the large eruption). Many shallow earthquakes were recorded over the next seven weeks. Magma moving higher and higher inside the mountain was causing these earthquakes. As the magma rose it formed a large bulge on the north flank. This bulge was growing daily and the geologists knew that an eruption was soon to be.

What the authorities did was evacutate most of the people in and near the mountain. Some decided to stay. Almost everyone that was near the eruption was instantly killed. In all, 57 people died. Without the evacuation perhaps as many as 30,000 deaths would have been attributed to Mt. St. Helens fury.

The geologists in the photo are measuring a growing fissure near the lava dome in Mt. St. Helens crater. As magma rises the fissure will grow wider telling the geologists that the magma is rising again.

Scientists can not stop a volcano from erupting but with constant monitoring they can warn and evacuate people and save lives.

Many volcanoes erupt in very consistant patterns, while other volcanoes have no eruption pattern at all. This makes forecasting eruptions difficult.

What makes predicting eruptions even more difficult is the fact that many volcanoes start with one type of eruption pattern and then change eruption patterns as they grow older.

Some of the most powerful eruptions in recorded time have come from volcanoes that have been dormant for hundreds and even thousands of years.

Here we have geologists studying a tilt meter. A tilt meter is used to measure the growth of the lavadome in the foreground. The tiltmeter will show a different angle as the dome grows. With careful study the geologists can tell if magma is on the rise and that an eruption may occur in the near future.

Write your answers to the following questions on a sheet of paper. Click on the Earth icon after you have finished to allow the next group to begin the lesson. You can click on page titles located directly under the questions to go back into the lesson to find the answers.

1. At what type of plate boundaries do volcanoes form?

2. What are the two definitions for the term volcano.

3. Write definitions in your own word for the following terms:

a) Active Volcano

b) Dormant Volcano

c) Extinct Volcano

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Volcanic activity is the most powerful force in nature. Some volcanic eruptions are much more powerful than the largest nuclear explosion. Volcanoes have killed thousands of people and have created some of the most frightening events in human history. Volcanoes have been the basis for myths and legends the world over.

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Volcanic eruption explained - Steven Anderson

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Earth Science for Kids: Rocks, Rock Cycle, and Formation

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Kids learn about the science of rocks and the rock cycle. How different types such as igneous, sedimentary, and metamorphic form from minerals with the help of nature.

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There are three main types of rocks: sedimentary, igneous, and metamorphic. Each of these rocks are formed by physical changes-such as melting, cooling, eroding, compacting, or deforming-that are part of the rock cycle.

Sedimentary rocks are formed from pieces of other existing rock or organic material. There are three different types of sedimentary rocks: clastic, organic (biological), and Sedimentary Rocks chemical. Clastic sedimentary rocks, like sandstone, form from clasts, or pieces of other rock. Organic sedimentary rocks, like coal, form from hard, biological materials like plants, shells, and bones that are compressed into rock.

The formation of clastic and organic rocks begins with the weathering, or breaking down, of the exposed rock into small fragments. Through the process of erosion, these fragments are removed from their source and transported by wind, water, ice, or biological activity to a new location. Once the sediment settles somewhere, and enough of it collects, the lowest layers become compacted so tightly that they form solid rock.

Chemical sedimentary rocks, like limestone, halite, and flint, form from chemical precipitation. A chemical precipitate is a chemical compound-for instance, calcium carbonate, salt, and silica-that forms when the solution it is dissolved in, usually water, evaporates and leaves the compound behind. This occurs as water travels through Earth's crust, weathering the rock and dissolving some of its minerals, transporting it elsewhere. These dissolved minerals are precipitated when the water evaporates.

Metamorphic rocks are rocks that have been changed from their original form by immense heat or pressure. Metamorphic rocks have two classes: foliated and nonfoliated. When a rock with flat or elongated minerals is put under immense pressure, the minerals line up in layers, creating foliation. Foliation is the aligning of elongated or platy minerals, like hornblende or mica, perpendicular to the direction of pressure that is applied. An example of this transformation can be seen with granite, an igneous rock. Granite contains long and platy minerals that are not initially aligned, but when enough pressure is added, those minerals shift to all point in the same direction while getting squeezed into flat sheets. When granite undergoes this process, like at a tectonic plate boundary, it turns into gneiss (pronounced "nice").

Nonfoliated rocks are formed the same way, but they do not contain the minerals that tend to line up under pressure and thus do not have the layered appearance of foliated rocks. Sedimentary rocks like bituminous coal, limestone, and sandstone, given enough heat and pressure, can turn into nonfoliated metamorphic rocks like anthracite coal, marble, and quartzite. Nonfoliated rocks can also form by metamorphism, which happens when magma comes in contact with the surrounding rock.

Igneous Rocks Metamorphic Rocks

Igneous rocks (derived from the Latin word for fire) are formed when molten hot material cools and solidifies. Igneous rocks can also be made a couple of different ways. When they are formed inside of the earth, they are called intrusive, or plutonic, igneous rocks. If they are formed outside or on top of Earth's crust, they are called extrusive, or volcanic, igneous rocks.

Granite and diorite are examples of common intrusive rocks. They have a coarse texture with large mineral grains, indicating that they spent thousands or millions of years cooling down inside the earth, a time course that allowed large mineral crystals to grow.

Alternatively, rocks like basalt and obsidian have very small grains and a relatively fine texture. This happens because when magma erupts into lava, it cools more quickly than it would if it stayed inside the earth, giving crystals less time to form. Obsidian cools into volcanic glass so quickly when ejected that the grains are impossible to see with the naked eye.

Extrusive igneous rocks can also have a vesicular, or "holey" texture. This happens when the ejected magma still has gases inside of it so when it cools, the gas bubbles are trapped and end up giving the rock a bubbly texture. An example of this would be pumice.

Director

Tyson Brown, National Geographic Society

Author

National Geographic Society

Production Managers

Gina Borgia, National Geographic Society

Jeanna Sullivan, National Geographic Society

Program Specialists

Sarah Appleton, National Geographic Society, National Geographic Society

Margot Willis, National Geographic Society

Last Updated

October 19, 2023

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The rock cycle is a series of processes that create and transform the types of rocks in Earth's crust.

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The plates have moved across Earth's surface for hundreds of millions of years. As the plates move, the continents on them move, too. This movement is called continental drift.

Scientists think that it takes about 500 million years for all the continents to join together into one big continent-or supercontinent-and then break apart again. A number of supercontinents have formed and broken apart on Earth over time. The most recent supercontinent, called Pangea (or Pangaea), had formed by about 270 million years ago. Pangea lay across a plate boundary. Slowly, Pangea broke apart at this boundary. Rising magma filled in the space, which eventually became the floor of the Atlantic Ocean.

One piece of Pangea included parts of what are now North America, Europe, and Asia. This piece, called Laurasia, drifted north. The other piece of Pangea included parts of what are now Antarctica, Africa, South America, and Australia. This part, called Gondwanaland, drifted south. Eventually Laurasia and Gondwanaland broke apart, too. The continents then slowly moved to the places they are now.

The continents continue to move today. Scientists believe that in about 250 million years they will join together again.

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The theory, or idea, of plate tectonics says that Earth's outer layer is made up of large, moving pieces called plates. All of Earth's land and water sit on these plates. The...

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The basic idea behind plate tectonics is that there are eight major plates on the surface of the Earth. There are also bunches of minor plates. The plates are like the skin of the planet. They constantly move around the planet. When we say constantly moving, we're talking centimeters each year. You couldn't sit down and watch it happen. Or can you? You could watch it happen if you watched an earthquake.

These plates make up the top layer of the Earth called the lithosphere. Directly under that layer is the asthenosphere. It's a flowing area of molten rock. There is constant heat and radiation given off from the center of the Earth. That energy is what constantly heats the rocks and melts them. The tectonic plates are floating on top of the molten rock and moving around the planet. Think of it as ice floating at the top of your soda. When the continents and plates move it's called continental drift.

Think of the molten rock in the asthenosphere, not as rock, but as a liquid. It has currents and it flows just like any other liquid. When the floating plates spread apart, it's called a spreading center. When they are moving together, it's called a subduction zone. When they are forced together, it is called a zone of convergence. One of the plates usually moves under the other in a zone of convergence. As the plate moves down into the asthenosphere it begins to melt. The place where they meet has a crack or a trench. Some of the deepest parts of the oceans are these trenches.

How do we back up these ideas? Scientists have traveled all over the Earth and found evidence that supports the ideas of plate tectonics. First, they looked at the continents. Ever notice how Africa and South America look like they could fit together? Scientists did. They cut up a map, moved the continents close together, and came up with a huge landmass called Pangaea (one super-continent).

Scientists also looked at the fossils (long-dead animal bones and plants) on the different continents. They found that fossils on Australia were similar to the ones in Southern Asia. They think the same plants once lived on the continents, but when they split apart, new plants developed. When they were digging, they also looked at the types of rocks. The West Coast of Africa has very similar rock formations to those on the East Coast of South America. They are too similar to be a coincidence.

Or search the sites for a specific topic.

Fossils and Plate Tectonics (NASA SciFiles Video)

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The basic idea behind plate tectonics is that there are eight major plates on the surface of the Earth. There are also bunches of minor plates. The plates are like the skin of the planet. They constantly move around the planet. When we say constantly moving, we're talking centimeters each year.

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Take a bottle of soda. Shake it really hard. Gas bubbles will form inside, causing a buildup of pressure. Twist the cap off. Pressure will release from the bottle. Soda will shoot everywhere.

A volcanic eruption works much the same way. Pressure builds up inside a volcano as gas bubbles form in magma. Magma is hot liquid rock beneath the surface of the Earth. Gas bubbles in the volcano need to escape. So the volcano erupts. Boom!

A volcano is a mountain or hill with an opening. When a volcano erupts, magma is pushed up through the opening with great force. When magma reaches the Earth's surface, it is called lava. Lava can be as hot as 2,200°F (1,204°C).

Some volcanic eruptions are explosive. Lava shoots into the sky. Gas and hot pieces of rock and ash are also released. Other eruptions are effusive × effusive LEOPATRIZI/GETTY IMAGES overflowing (adjective) My effusive friend is enthusiastic about everything she does. . Lava oozes slowly from the volcano.

The intensity of an eruption depends on a few factors. One is the magma's temperature. Another is the magma's thickness. The amount of gas trapped within the magma is also an important factor.

GETTY IMAGES

The Ring of Fire

About 75% of the Earth's volcanoes are located in a region called the Ring of Fire. This 25,000-mile "ring' is located around the Pacific Ocean. It runs from the southern tip of South America and up the west coast of North America. It continues across the Bering Strait and then south through Japan to New Zealand.

The ring sits along the outline of several tectonic plates. Tectonic plates are the large puzzle pieces that make up the Earth's crust. The crust is Earth's outer layer. Most volcanoes form at the edges of tectonic plates. These huge plates are constantly shifting. Sometimes, the plates pull apart or slide into each other. When this happens, magma rises to fill in the space. Strong pressure and intense heat force the magma upward. It squeezes upward like toothpaste through a tube.

Heating Up

Volcanoes can be dangerous-especially to the millions of people around the world who live near one. When a volcano erupts, lava, hot ash, steam, and rocks are released. In addition, volcanic eruptions can cause other natural disasters. These include landslides, mudslides, earthquakes, and tsunamis.

The most destructive volcanic event in U.S. history occurred in 1980. That is when Mount Saint Helens, in Washington State, erupted. The eruption destroyed entire forests. It killed 57 people. Mount Saint Helens is located within the Ring of Fire. It is a composite volcano, or stratovolcano. This is the most common type of volcano. It is tall and cone-shaped. A composite volcano is made up of layers of rock and ash. Its eruptions are often violent.

Another historically important volcanic event occurred in 79 A.D. in Italy. That is when Mount Vesuvius erupted. It buried the city of Pompeii in lava and ash. The city and its people were lost. Centuries later, scientists discovered their remains.

Volcanoes can be destructive. But they can also create new land. The Hawaiian Islands were created by the eruptions of shield volcanoes. These large, low-lying volcanoes are made up almost entirely of layers of hardened lava.

Another type of volcano is the cinder cone. These shoot lava into the air like a sputtering fountain. A cinder cone eruption often comes from a single volcanic vent in the Earth's crust. Lava cools quickly in the air. It hardens into glassy rocks around the volcano's opening. One example of a cinder cone volcano is Sunset Crater, in Arizona.

ARCTIC-IMAGES/GETTY IMAGES

A Powerful Force

Volcanoes have played an important role in shaping our Earth. Ash from volcanoes adds helpful minerals to soil. This helps plants grow strong. Healthy plants produce oxygen for humans and animals to breathe. Volcanoes also remove heat from the Earth's interior. This helps keep our planet cool.

In recent years, a new benefit of volcanoes has surfaced. Scientists are turning to volcanoes to help power cities. Researchers are exploring geothermal energy. It involves tapping into the heat beneath the Earth's surface to generate electricity. In Iceland, 25% of the nation's energy is geothermal.

Volcanoes may be unpredictable. But as we learn more about how they work, they will become even more important to life on Earth.

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Take a bottle of soda. Shake it really hard. Gas bubbles will form inside, causing a buildup of pressure. Twist the cap off. Pressure will release from the bottle. Soda will shoot everywhere. A volcanic eruption works much the same...

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How Volcanoes Form

In 1980 in Washington, after 123 years of hibernation, Mount St. Helens erupted. The blast destroyed and scorched 230 square miles (370 square kilometers) of forest within minutes. The eruption released an avalanche of hot ash, gas, steam, and rocks that mowed down giant trees up to 15 miles (24 kilometers) away.

When magma finds a way to escape from beneath the earth's surface, it creates a volcano.

Volcanoes erupt in different ways. Some, like Mount St. Helens, explode. Explosive eruptions are so powerful, they can shoot particles 20 miles up (32 kilometers), hurl 8-ton boulders more than a half mile (0.8 kilometers) away, and cause massive landslides. Explosive eruptions also create an avalanche of hot volcanic debris, ash, and gas that bulldozes everything in its path. Explosive volcanoes cause most of the volcano-related fatalities.

Volcanoes, like Mauna Loa in Hawaii, are effusive. Rather than a violent explosion, lava pours or flows out. Fatalities from effusive volcanoes are rare because people can usually outrun the lava. However, some people get too close or become trapped with no escape. The flowing lava burns, melts, and destroys everything it touches including farms, houses, and roads.

A volcanic eruption forever changes the landscape. Though volcanoes destroy, they also create mountains, islands, and, eventually, incredibly fertile land.

Carpet of Ash

Volcanic eruptions can cause damage hundreds of miles away. Volcanic ash causes airplane engines to fail, destroys crops, contaminates water, and damages electronics and machinery. The ash carpets the ground, burying everything, sometimes even causing buildings to collapse. Mount St. Helens produced more than 490 tons of ash that fell over a 22,000 square mile (56,980 square kilometer) area and caused problems in cities 370 miles (600 kilometers) away.

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When magma finds a way to escape from beneath the earth's surface, it creates a volcano.

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Volcanoes form when magmas make their way to the Earth's surface and erupt. Volcanoes vary by type; cinder cones, stratovolcanoes or shield volcanos. The intensity of the eruption depends in part on the composition if the lava, and following, how much gas is contained within the melt and how viscous (reseitive to flow) the magma is upon reaching the Earth's surface.

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Kid's learn about the science of earthquakes. What causes them and where they happen.

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In an earthquake, huge masses of rock move beneath the Earth's surface and cause the ground to shake. Earthquakes occur constantly around the world. Often they are too small...

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The forces that cause weathering may be physical, chemical, or biological. Often, weathering results from a combination of forces.

Physical forces include changes in temperature or pressure, freezing or moving water, and wind. An increase in temperature may cause rock to expand. As the rock cools, it contracts, or shrinks. The expanding and contracting may cause the rock to crack and break apart. If heavy material on top of a rock is removed (by a glacier, for example), the pressure on the rock decreases. The release of pressure may cause the rock to split. Water that freezes inside cracks in a rock may widen the cracks. Particles carried by water or wind may slowly scrape away a rock's surface.

In chemical weathering, the minerals that make up the rock are changed. Water usually is involved in chemical weathering. Elements in the water may react with the minerals in the rock. The minerals may break down or form different minerals.

Biological weathering results from the actions of living things. The roots of plants may reach inside rock openings. Over time, they may push apart sections of rock. Lichens grow on rock surfaces or within cracks. They may wear down rock or etch patterns on its surface.

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The forces that cause weathering may be physical, chemical, or biological. Often, weathering results from a combination of forces. Physical forces include changes in temperature or pressure, freezing or moving water, and wind. An increase in temperature may cause rock to expand. As the rock cools, it contracts, or shrinks.

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Let's say you made a cake and left it outside. What would happen? Maybe it would dry up and crack in the hot sun. Or perhaps rain would wash it away. If it froze, it might crack too. This process would probably take just a few days.

The Earth - and the rocks on the Earth - is a bit like that cake. The surface of the Earth is constantly being changed due to weathering processes. This process can take millions of years or happen relatively quickly.

Fun Facts about Weathering for Kids

Rain is mildly acidic and it slowly eats away rocks. Rain slowly dissolves limestone. It turns the feldspar in granite into soft clay. The remaining quartz crystals are often crushed into grains of sand.

Plants and microbes also attack rocks. All living things need elements, such as copper, potassium and iron, as nutrients. These minerals are found within rocks. Lichens grow on rocks and release acids to dissolve the minerals in them. Plant roots slowly grow into rocks, forcing them apart.

In cold areas, water seeps into cracks in the rocks during the day. At night, the water freezes and expands, cracking the rocks even more. This continual freeze and thaw cycle causes rocks to splinter and break into small pieces.

In the desert, rocks expand during the heat of the day and contract at night when temperatures cool. Sheets of rock slowly flake away.

Weathering Vocabulary

Learn More All About Weathering

Check out this cool video about Weathering for kids:

This video explains the factors and the process of weathering.

Weathering Q&A

Question: How are the types of weathering described?

Answer: Chemical weathering occurs when a chemical, such as acid rain, breaks down rocks. Mechanical weathering is the process of weathering through external forces, such as freeze and thaw cycles. When plants or microbes break down rocks, the process is known as organic weathering.

Enjoyed the Geography for Kids all about Weathering info? Take the FREE & fun all about Weathering quiz and download FREE Weathering worksheet for kids. For lengthy info click here.

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Let's say you made a cake and left it outside. What would happen? Maybe it would dry up and crack in the hot sun. Or perhaps rain would wash it away. If it froze, it might crack too. This process would probably take just a few days.

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Kids learn about the Earth science subject of erosion including water, wind, and glacial erosion, fun facts, human causes, and controlling it.

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What Are Natural Processes?

Natural processes (also known as ecological processes) are interactions among plants, animals, and the environment that occur naturally (without purposeful intervention by people). They are just as critical to the identity of natural communities as are the plants and animals that make up the communities. They also help maintain the health of natural communities.
Ecobit: Natural Processes as Pathways for Nutrients and Energy
Let's look more closely at a few natural processes that are particularly important for understanding the natural communities we see at Rock Creek Park today. These are just a tiny fraction of all the natural processes busy at work, noticed or unnoticed, shaping natural communities.

Fire

Fire is a natural disturbance that can help maintain dry hilltop communities, such as Rock Creek Park's Chestnut Oak / Mountain Laurel Forest and Mixed Oak / Heath Forest by weeding out plant species that won't survive fire over the long term, as well as by weeding out diseased vegetation.
Ecobit: Fire-Rising From the Ashes
In these hilltop natural communities, the predominance of species that respond well to fire indicates that repeated fires were likely an important natural disturbance here historically. Lightning strikes often start fires. Once started, fire tends to move upslope in dry areas and run along ridgelines. 1

Floods

Another natural disturbance, flooding, is important for maintaining the Tuliptree Small-Stream Floodplain Forest. This community's plant species, such as American sycamore and river birch, thrive through frequent flooding that might kill a dry-adapted chestnut oak.
Ecobit: Floods-Rich but Hard to Live With
Canopy Gap Regeneration

An important natural disturbance in forests is the creation of gaps in the canopy when large trees fall due to diseases or storms. Seedlings and saplings on the forest floor take advantage of the newly available sunlight to grow and join the canopy.
Ecobit: Canopy Gaps-Room to Grow Ecobit: Oaks-Shade Tolerant?
Herbivory

Herbivory is the consumption of plants by animals (including insects). It's an important part of what keeps plant populations at Rock Creek Park from exploding! What would the park look like if every single seed produced there grew up to be a full-sized plant?
Ecobit: Herbivory-A Balanced Diet
Erosion and Sediment Transport

Erosion and sedimentation are most evident in the Tuliptree Small-Stream Floodplain Forest in Rock Creek Park.

However, sediments creep or slide downslope in in other areas as well. For examples, ancient river on ridgetops gradually move downhill, affecting the soils in natural communities downslope. itself also washes downslope, leading to thinner soils on steeper slopes and thicker soils on flatter or landforms.
Ecobit: Erosion and Sediment Transport-Earth in Motion
Processes Affecting Soils

Many natural processes in Rock Creek Park interact to determine soil characteristics, such as depth, moisture content, composition, and texture. These characteristics, in turn, determine where different natural communities can be found.
Ecobit: Soil Processes-Creating a Place to Take Root
Soil moisture is an obvious factor in determining what plants can grow where. On ridgetops and upper slopes in Rock Creek Park, exposure to sun and wind create dry soils that support the Chestnut Oak / Mountain Laurel Forest and Mixed Oak / Heath Forest.

The Mesic Mixed Hardwood Forest, on the other hand, grows in soil that is mesic-not too wet, not too dry. Mesic soils tend to be found in areas protected from extremes in climate, such as lower slopes and rolling . The Coastal Plain Oak Forest and the Basic Mesic Hardwood Forest also occur on mesic soils.

In the lower elevations of the park, along Rock Creek and its tributaries or at the base of hills, you'll find natural communities growing in soils that can be quite wet, with the moisture being supplied by groundwater or floods. These wetland communities are the Tuliptree Small-Stream Floodplain Forest and the Red Maple Seepage Swamp.

The depth of soil varies across the park as well. The Oak - Beech / Heath Forest survives on steep slopes where erosion and gravity prevent much soil from accumulating.

In contrast, the Basic Mesic Hardwood Forest is found in areas with deep accumulations of soils, such as concave slopes.

Furthermore, the composition of the soils that support the Basic Mesic Hardwood Forest are relatively rich compared to other soils in the park. The nutrients of these rich soils may be supplied by the composition of underlying or sediments, or nearby nutrient-rich groundwater.

The Water Cycle

Rock Creek Park's streams, tributaries, springs, and groundwater seeps are all part of the water cycle, which plays a central role in Rock Creek Park's natural communities.

The Red Maple Seepage Swamp and Tuliptree Small-Stream Floodplain Forest depend on a steady source of water, whether from groundwater or flooding. Less water cycles through the high and dry Chestnut Oak / Mountain Laurel Forest and Mixed Oak / Heath Forest, and that water comes mostly in the form of precipitation rather than flooding or groundwater.
Ecobit: The Water Cycle-What Goes Around, Comes Around
Forest Succession

Prior to the formation of the park in 1890, much of the land that became Rock Creek Park had been recently disturbed by logging, farming/orchard planting, and Civil War clear-cutting.
Map tip: To find the Civil War forts closest to Rock Creek, search for "fort" on the interactive map of Rock Creek Park and select results under Historic Sites.
Most of these areas have had many years to recover, and may look like they've been there always, but the composition of these forests tells us that they have grown up on sites that were formerly cleared. These are called successional forests.
Ecobit: Forest Succession-Clues to the Past
Successional forests contain clues that can indicate whether the area was logged or whether it experienced more extreme disruption, such as plowing or earth-moving.

However, it's not always possible to accurately guess a piece of land's history strictly by reading the current forest growth. For example, at Fort DeRussy today, we see mature chestnut oak and northern red oak trees, and very little else. A typical natural community would have a better-developed understory. A typical successional community would be made up of mostly non-oaks. We don't know the precise history of the vegetation at Fort DeRussy that led to this anomalous combination. Any number of unknown variables (in this case probably human-induced ones) may have impacted the site during and since its clearing.

Learn about Rock Creek Park's successional forests.

When Natural Processes Are Interrupted

Ever since urbanization spread around the park in the 1900's, fires have needed to be suppressed. Read about the impact of fire suppression on Rock Creek Park's driest hilltop natural communities and historic meadows, and the ways natural resource managers are trying to simulate the historic benefits of fire, in Current Water and Land Use | Fire Suppression.

Urbanization has interrupted several natural processes by routing stormwater runoff from streets directly into creeks. Read about the stewardship challenges that arise at Rock Creek Park in the areas of flooding, erosion, soil processes, and water cycling (as less water can soak into the ground and make its way to the creek as groundwater, and more water is directed to flow through the Rock Creek stream channel), in Current Water and Land Use | Water Issues.

Population explosions of white-tailed deer and non-native invasive insects such as gypsy moth can take the natural process of herbivory to destructive lengths! Read about these threats and the park natural resource managers' response to them, in Population Dynamics and Non-Native Invasive Insects.

Extreme summer or winter storms can create extensive holes in forests (rather than limited canopy gaps). Read about the special challenges this creates in modern times for forest succession at Rock Creek Park, in Climate and Weather | Severe Natural Disturbances.

Rock Creek Park deals with stewardship challenges related to several of these natural processes. See Stewardship and Ecological Threats at Rock Creek Park.

# data[].attributes.attachment_link.description
Natural processes (also known as ecological processes) are interactions among plants, animals, and the environment that occur naturally (without purposeful intervention by people). They are just as critical to the identity of natural communities as are the plants and animals that make up the communities. They also help maintain the health of natural communities.

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Eroding stream banks threaten homes along Rock Creek, city funds repairs

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The city of Frederick has agreed to cost-share $450,000 worth of repairs to Rock Creek to protect Waterford Park and townhouses in the Waterford community.

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A rehabilitation and pedestrian bridge project that will shore up D.C.'s existing Rock Creek Park Trail is getting underway this week.

The District Department of Transportation, along with the National Park Service, jointly announced that work starts Wednesday.

The plan is to improve more than 3.7 miles worth of the multi-use trail spanning Wards 1 through 4, from M Street NW in Georgetown all the way up to Broad Branch Road NW.

"We are thrilled to finally start construction on this project, which is the result of decadeslong collaboration with our partners and community stakeholders," said DDOT Interim Director Everett Lott in a news release.

Construction will target storm drains and a retaining wall, stabilize the stream bank, and also widen the paved trail.

The existing paved trail's width will extend to between 8 and 10 feet. Crews will also use more absorbent pavement to improve its durability by combining dense mix and porous asphalt.

The series of improvements will redirect stormwater away from the trail to reduce erosion and maintenance.

Another big part of the project includes the installation of a 110-foot long pedestrian bridge that will sit just south of the Beach Drive tunnel close to the National Zoo.

A portion of stream bank and trail that previously collapsed and fell apart near the zoo will also be repaired and resurrected for use.

Close to a mile of new trail will stretch along Piney Branch Parkway between Beach Drive and Arkansas Avenue NW.

DDOT and NPS said the project will require occasional shutdowns of park trails and Beach Drive.

Construction will take place in seven phases with a projected completion date of spring 2023.

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Work begins on Rock Creek Park Trail pedestrian bridge, trail rehab | WTOP News

# data[].attributes.attachment_link.description
A rehabilitation and pedestrian bridge project that will shore up D.C.'s existing Rock Creek Park Trail is getting underway this week. The District Department of Transportation, along with the National Park Service, jointly announced that work starts Wednesday.

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Kids learn about the science of volcanoes including how they form mountains, lava, and magma; types such as cinder cone, composite, and shield; watch a video about volcanoes.

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About Volcanoes | U.S. Geological Survey

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Volcanoes are openings, or vents where lava, tephra (small rocks), and steam erupt on to the Earth’s surface. Many mountains form by folding, faulting, uplift, and erosion of the Earth’s crust. Volcanic terrain, however, is built by the slow accumulation of erupted lava. The vent may be visible as a…

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Previewing Just Add Water - Instant Erosion.pdf

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Great ShakeOut Earthquake Drills help people in homes, schools, and organizations worldwide improve preparedness and practice how to be safe during earthquakes. Register to participate in your state or country’s drill at www.ShakeOut.org.

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Rock Creek Park Waterway Restoration: How to Prevent Erosion

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Last year, RTEC Treecare assisted Rock Creek Park in Washington, D.C, to restore the waterway that was damaged from erosion. Over the years the stream bank began to show signs of serious erosion, and eventually, the stream became clogged with plant debris.