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http://www.onegeology.org/extra/kids/earthProcesses/weathering.html

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Home > eXtra > OneGeology Kids > Earth processes > Weathering and erosion

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We started talking about weathering in the erosion sections. Mechanical weathering is the process of breaking big rocks into little ones. This process usually happens near the surface of the planet. Temperature also affects the land. The cool nights and hot days always cause things to expand and contract. That movement can cause rocks to crack and break apart. Roots and plants also push into the rocks and break them apart. They act like wedges and push the rocks apart. Little animals also help by burrowing and digging through the ground.

Scientists have observed a process called freeze-thaw. That process occurs when the water inside of rocks freezes and expands. That expansion cracks the rocks from the inside and eventually breaks them apart. The freeze-thaw cycle happens over and over again and the break finally happens. Another word for it is frost wedging. There are already some small cracks in boulders and water can get in the cracks. When that water expands, the rock is crunched between two expanding pieces of ice instead of being forced apart into separate pieces.

Another type of mechanical weathering is called salt wedging. When it rains and water flows everywhere, it usually has ions and salts dissolved inside. Have you seen salt water dry up? Salt crystals are left over. Those crystals happen in nature, too. The water flows in a rock and evaporates. Crystals slowly begin to grow. Those crystals act like a wedge and crack the rocks.

Chemical weathering includes the effect of weathering on molecules and atoms. As with all chemistry, the greater the surface area of an object, the more chemical reactions can take place. For these chemical reactions to happen in nature, moisture, and heat must be present.

Reactions such as oxidation, hydrolysis, and acidification can happen when all of the elements are together. Oxidation makes rocks softer. It is similar to an iron bar rusting. Since there is a lot of iron in many rocks, oxidation often happens. Hydrolysis usually causes rocks to expand and then mechanical weathering can begin. These chemical reactions are happening all of the time. When you see rocks next to each other that are different colors (often shades of red) then you know chemical reactions have taken place.

Biological weathering would include the effect of animals and plants on the landscape. This is more than roots digging in and wedging rocks. Biological weathering is the actual molecular breakdown of minerals. There are things called lichens (combinations of fungi and algae) which live on rocks. Lichens slowly eat away at the surface of rocks. The amount of biological activity that breaks down minerals depends on how much life is in that area. You might find more activities like lichens near oceans where the air is humid and cooler.

Or search the sites for a specific topic.

Melting Mountain Glaciers (US-NSF Video)

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We started talking about weathering in the erosion sections. Mechanical weathering is the process of breaking big rocks into little ones. This process usually happens near the surface of the planet. Temperature also affects the land. The cool nights and hot days always cause things to expand and contract.

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https://www.nationalgeographic.org/encyclopedia/erosion/#:~:text=The%20action%20of%20erosion%20can,rock%20columns%20called%20sea%20stacks.

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Erosion is the opposite of deposition, the geological process in which earthen materials are deposited, or built up, on a landform.

Most erosion is performed by liquid water, wind, or ice (usually in the form of a glacier). If the wind is dusty, or water or glacial ice is muddy, erosion is taking place. The brown color indicates that bits of rock and soil are suspended in the fluid (air or water) and being transported from one place to another. This transported material is called sediment.

Physical erosion describes the process of rocks changing their physical properties without changing their basic chemical composition. Physical erosion often causes rocks to get smaller or smoother. Rocks eroded through physical erosion often form clastic sediments. Clastic sediment s are composed of fragments of older rocks that have been transported from their place of origin.

Landslides and other forms of mass wasting are associated with physical weathering. These processes cause rocks to dislodge from hillsides and crumble as they tumble down a slope.

Plant growth can also contribute to physical erosion in a process called bioerosion. Plants break up earthen materials as they take root, and can create cracks and crevice s in rocks they encounter.

Ice and liquid water can also contribute to physical erosion as their movement forces rocks to crash together or crack apart. Some rocks shatter and crumble, while others are worn away. River rocks are often much smoother than rocks found elsewhere, for instance, because they have been eroded by constant contact with other river rocks.

Liquid water is the major agent of erosion on Earth. Rain, rivers, floods, lakes, and the ocean carry away bits of soil and sand and slowly wash away the sediment.

Rainfall produces four types of soil erosion: splash erosion, sheet erosion, rill erosion, and gully erosion.

* Splash erosion describes the impact of a falling raindrop, which can scatter tiny soil particles as far as .6 meters (2 feet).

* Finally, gully erosion is the stage in which soil particles are transported through large channels. Gullies carry water for brief periods of time during rainfall or snowmelt but appear as small valleys or crevasses during dry season s.

Valley erosion is the process in which rushing streams and rivers wear away their banks, creating larger and larger valleys. The Fish River Canyon, in southern Namibia, is the largest canyon in Africa and a product of valley erosion. Over millions of years, the Fish River wore away at the hard gneiss bedrock, carving a canyon about 160 kilometers (99 miles) in length, 27 kilometers (17 miles) wide, and 550 meters (1,084 feet) deep.

The ocean is a huge force of erosion. Coastal erosion-the wearing away of rocks, earth, or sand on the beach-can change the shape of entire coastlines. During the process of coastal erosion, waves pound rocks into pebbles and pebbles into sand. Waves and currents sometimes transport sand away from beach es, moving the coastline farther inland.

Coastal erosion can have a huge impact on human settlement as well as coastal ecosystems. The Cape Hatteras Lighthouse, for example, was nearly destroyed by coastal erosion. The Cape Hatteras Lighthouse was built on the Outer Banks, a series of barrier islands off the coast of the U.S. state of North Carolina, in 1870. At the time, the lighthouse was nearly 457 meters (1,500 feet) from the ocean. Over time, the ocean eroded most of the beach near the lighthouse. By 1970, the pounding surf was just 37 meters (120 feet) away and endanger ed the structure. Many people thought the lighthouse would collapse during a strong storm. Instead, thanks to a significant engineering feat completed in 1999, it was moved 880 meters (2,900 feet) inland.

The battering force of ocean waves also erodes seaside cliffs. The action of erosion can create an array of coastal landscape features. For example, erosion can bore holes that form caves. When water breaks through the back of the cave, it can create an arch. The continual pounding of waves can cause the top of the arch to fall, leaving nothing but rock columns called sea stack s. The seven remaining sea stacks of Twelve Apostles Marine National Park, in Victoria, Australia, are among the most dramatic and well-known of these features of coastal erosion.

Wind is a powerful agent of erosion. Aeolian (wind-driven) processes constantly transport dust, sand, and ash from one place to another. Wind can sometimes blow sand into towering dunes. Some sand dune s in the Badain Jaran section of the Gobi Desert in China, for example, reach more than 400 meters (1,300 feet) high.

In dry areas, windblown sand can blast against a rock with tremendous force, slowly wearing away the soft rock. It polishes rocks and cliffs until they are smooth-giving the stone a so-called " desert varnish." Wind is responsible for the eroded features that give Arches National Park, in the U.S. state of Utah, its name.

Wind can also erode material until little remains at all. Ventifacts are rocks that have been sculpted by wind erosion. The enormous chalk formations in the White Desert of Egypt are ventifacts carved by thousands of years of wind roaring through the flat landscape.

Some of the most destructive examples of wind erosion are the dust storms that characterized the " Dust Bowl" of the 1930s in North America. Made brittle by years of drought and agricultural mismanagement, millions of tons of valuable topsoil were eroded away by strong winds in what came to be known as "black blizzards." These dust storms devastated local economies, forcing thousands of people who depended on agriculture for their livelihoods to migrate.

Ice, usually in the form of glaciers, can erode the earth and create dramatic landforms. In frigid areas and on some mountaintops, glaciers move slowly downhill and across the land. As they move, they transport everything in their path, from tiny grains of sand to huge boulders.

Rocks carried by glaciers scrape against the ground below, eroding both the ground and the rocks. In this way, glaciers grind up rocks and scrape away the soil. Moving glaciers gouge out basins and form steep-sided mountain valleys. Eroded sediment called moraine is often visible on and around glaciers.

Several times in Earth's history, vast glaciers covered parts of the Northern Hemisphere. These glacial periods are known as ice age s. Ice Age glaciers carved much of the modern northern North American and European landscape.

Ice Age glaciers scoured the ground to form what are now the Finger Lakes in the U.S. state of New York, for example. They carved fjords, deep inlets along the coast of Scandinavia. The snout of a glacier eroded Cape Cod Bay, Massachusetts, and formed the recognizable fishhook shape of Cape Cod itself.

Today, in places such as Greenland and Antarctica, glaciers continue to erode the earth. Ice sheets there can be more than a mile thick, making it difficult for scientists to measure the speed and patterns of erosion. However, ice sheets do erode remarkably quickly-as much as half a centimeter (.2 inch) every year.

Mass wasting describes the downward movement of rocks, soil, and vegetation. Mass wasting incidents include landslides, rockslides, and avalanches. Mass wasting can erode and transport millions of tons of earth, reshaping hills and mountains and, often, devastating communities in its path.

Factors Impacting Erosion

Some of the natural factors impacting erosion in a landscape include climate, topography, vegetation, and tectonic activity.

Climate is perhaps the most influential force impacting the effect of erosion on a landscape. Climate includes precipitation and wind. Climate also includes seasonal variability, which influences the likelihood of weathered sediments being transported during a weather event such as a snowmelt, breeze, or hurricane.

Topography, the shape of surface features of an area, can contribute to how erosion impacts that area. The earthen floodplains of river valleys are much more prone to erosion than rocky flood channels, which may take centuries to erode. Soft rock like chalk will erode more quickly than hard rocks like granite.

Vegetation can slow the impact of erosion. Plant roots adhere to soil and rock particles, preventing their transport during rainfall or wind events. Trees, shrub s, and other plants can even limit the impact of mass wasting events such as landslides and other natural hazards such as hurricanes. Deserts, which generally lack thick vegetation, are often the most eroded landscapes on the planet.

Finally, tectonic activity shapes the landscape itself, and thus influences the way erosion impacts an area. Tectonic uplift, for example, causes one part of the landscape to rise higher than others. In a span of about 5 million years, tectonic uplift caused the Colorado River to cut deeper and deeper into the Colorado Plateau, land in what is now the U.S. state of Arizona. It eventually formed the Grand Canyon, which is more than 1,600 meters (1 mile) deep and as much as 29 kilometers (18 miles) wide in some places.

Deposition, Soils, and Sediments

Eroded sediments have profoundly influenced the development of civilizations around the world.

River deltas are made almost entirely of sediment that has eroded from the banks and bed of a river. The rich delta soils of the San Joaquin and Sacramento rivers in northern California, for example, have created one of the most agriculturally productive areas in the world.

Loess is an agriculturally rich sediment made almost entirely of wind-blown, eroded sediment. The Yellow River in central China gets its name from the yellow loess blown into and suspended in its water. The fertile lands around the Yellow River have been among China's most productive for thousands of years.

Erosion is a natural process, but human activity can make it happen more quickly.

Human activity altering the vegetation of an area is perhaps the biggest human factor contributing to erosion. Trees and plants hold soil in place. When people cut down forests or plow up grasses for agriculture and development, the soil is more vulnerable to washing or blowing away. Landslides become more common. Water rushes over exposed soil rather than soaking into it, causing flooding.

The rise in temperature is also quickly melting glaciers. The slower, more massive form of glacial erosion is being supplanted by the cumulative impact of rill, gully, and valley erosion. In areas downstream from glacial snouts, rapidly melting glaciers are contributing to sea level rise. The rising sea erodes beaches more quickly.

Sometimes, engineers simply install structures to physically prevent soil from being transported. Gabions are huge wireframes that hold boulders in place, for instance. Gabions are often placed near cliffs. These cliffs, often near the coast, have homes, businesses, and highways near them. When erosion by water or wind threatens to tumble the boulders toward buildings and cars, gabions protect landowners and drivers by holding the rocks in place.

Erosion control also includes physically changing the landscape. Communities often invest in windbreaks and riparian buffers to protect valuable agricultural land. Windbreaks, also called hedgerows or shelterbelt s, are lines of trees and shrubs planted to protect cropland from wind erosion. Riparian buffers describe plants such as trees, shrubs, grasses, and sedges that line the banks of a river. Riparian buffers help contain the river in times of increased stream flow and flooding.

Living shorelines are another form of erosion control in wetland areas. Living shorelines are constructed by placing native plants, stone, sand, and even living organisms such as oysters along wetland coasts. These plants help anchor the soil to the area, preventing erosion. By securing the land, living shorelines establish a natural habitat. They protect coastlines from powerful storm surges as well as erosion.

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Erosion is the opposite of deposition, the geological process in which earthen materials are deposited, or built up, on a landform. Most erosion is performed by liquid water, wind, or ice (usually in the form of a glacier). If the wind is dusty, or water or glacial ice is muddy, erosion is taking place.

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https://www.softschools.com/quizzes/science/weathering_and_erosion/quiz448.html

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https://www.soils4kids.org/games

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Check out these fun soil games we've collected from around the web.

Soil Tris

Build a soil profile with sand, silt and clay blocks like you are playing Tetris®. Remember not to pack the particles too tightly though - soil must be loosely packed for the best results.
https://seedsurvivor.com/just-for-kids/games/Play Now

A-Maze-ing Underground

Play this Pac Man™ like game to create the perfect balance of nutrients for a crop of corn. While you are down there, take lots of pictures to review later!

https://seedsurvivor.com/just-for-kids/games/

Find the right water balance for corn plants. If you do well, you will get more plants that need attention. https://seedsurvivor.com/just-for-kids/games/
Play Now

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Check out these fun soil games we've collected from around the web. Soil Tris Build a soil profile with sand, silt and clay blocks like you are playing Tetris®. Remember not to pack the particles too tightly though - soil must be loosely packed for the best results.

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Weathering, Erosion and Deposition Games

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Weathering, Erosion and Deposition Games

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https://reviewgamezone.com/game.php?id=261

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Weathering, Erosion, Deposition (5th) Games (ID: 261)

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Play Weathering, Erosion, Deposition (5th) games in an arcade style format! Review games like Crazy Taxi, Pacman and Soccer merged with trivia questions about Weathering Erosion And Deposition For The 5th Grade TEKS to review and study for tests (261).

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http://planeta42.com/geography/earthstructure/

https://www.brainpop.com/games/timezonexearthsstructure/

https://online.seterra.com/en/vgp/3254

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https://www.natgeokids.com/uk/discover/geography/physical-geography/structure-of-the-earth/#!/register