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They can speed across the ocean as fast as a jet plane, swallow up islands and wipe out villages.

But what causes tsuamis...? Join National Geographic Kids and dive into our tsunami facts to find out!

What causes a tsunami?

Meaning " great harbour wave" in Japanese, tsunamis are sometimes called "tidal waves" but their strength has nothing to do with the tides. About four out of five tsunamis happen within the Ring Of Fire, a zone in the Pacific Ocean where earthquakes and volcanic eruptions frequently take place.

Giant slabs of the Earth's crust, called tectonic plates, grind together. Sometimes, though, the plates get stuck, the pressure builds up and they suddenly slam into a new position. This causes an earthquake. If an earthquake lifts or drops part of the ocean floor, the water above rises and starts spreading across the ocean, causing a tsunami. Underwater landslides or volcanic eruptions can also displace water (cause water to spread across the ocean) and may lead to a tsunami.

How big is a tsunami?

Out in the open ocean, tsunami waves are only about one-metre high because the water is deep. However, as the water becomes shallow, the waves slow down and begin to grow. They can rise 35m or higher - that's the same as a 10-floor block of flats! However, the scariest thing about a tsunami is its wavelength, as this determines how far inland it can travel. Whereas a large wave caused by a storm might have a wavelength of up to 150m, a tsunami could reach up to a fearsome 1,000km!

How fast is a tsunami?

A normal wind wave travels at about 90kmh, but a tsunami can race across the ocean at an incredible 970kmh! Sometimes, before a tsunami hits, there is a huge vacuum effect, sucking water from harbours and beaches. People can see the ocean floor littered with flopping fish and other sea animals. Then a wave blasts onto the shore minutes later, then another and another for two hours or more. There may also be up to one hour between each wave.

Can you predict when a tsunami is coming?

To save lives, scientists established the Pacific Tsunami Warning System, based in Hawaii, in the USA. Its network of detectors can track quakes that may cause a tsunami. These waves can race from one side of the Pacific Ocean to the other in less than a day, so people need to be warned in time to head for higher ground!

What do you think of these tsunami facts? Let us know by leaving a comment, below!

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Tsunami facts: check out the mighty wave! - National Geographic Kids

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Check out these epic tsunami facts from National Geographic Kids! How do tsunamis form? And how big are they? Find out all about them in our tsunami facts...

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What is a tsunami?
A tsunami is a large ocean wave usually caused by an underwater earthquake or a volcanic explosion. Tsunamis are NOT tidal waves. Tidal waves are caused by the forces of the moon, sun, and planets upon the tides, as well as the wind as it moves over the water. With typical waves, water flows in circles, but with a tsunami, water flows straight. This is why tsunamis cause so much damage!

How are tsunamis generated?
Tsunamis are generated by any large, impulsive displacement of the sea level. The most common cause of a tsunami is sea floor uplift associated with an earthquake. Tsunamis are also triggered by landslides into or under the water surface, and can be generated by volcanic activity and meteorite impacts.

How often do tsunamis occur?
On the average, two tsunamis occur per year throughout the world which inflict damage near the source. Approximately every 15 years a destructive, ocean-wide tsunami occurs.

Can strike-slip (horizontal motion) earthquakes trigger tsunamis?
Yes, approximately 10-15% of damaging tsunamis are triggered by strike-slip earthquakes. This type of earthquake is less likely to trigger a tsunami than one with vertical motion. The waves are likely generated by associated landslides or motion of a sloping bathymetric feature. Tsunamis generated by strike-slip earthquakes normally affect regions near the source only.

What does the word "tsunami" mean?
Tsunami (soo-NAH-mee) is a Japanese word meaning harbor wave.

How fast do tsunamis travel?
Tsunami velocity depends on the depth of water through which it travels. Velocity equals the square root of the product of the water depth times the acceleration of gravity. Tsunamis travel approximately 475 mph in 15,000 feet of water. In 100 feet of water the velocity drops to about 40 mph.

Did you know...A tsunami travels from the central Aleutian Islands to Hawaii in about 5 hours and to California in about 6 hours, or from the Portugal coast to North Carolina in about 8.5 hours.

How big is a tsunami?
Tsunamis range in size from inches to over a hundred feet. In deep water (greater than 600 feet), tsunamis are rarely over 3 feet and are not normally noticed by ships due to their long period or time between crests. As tsunamis propagate into shallow water, the wave height can increase by over 10 times. Tsunami heights vary greatly along a coast. The waves can be amplified by shoreline and sea floor features. A large tsunami can flood low-lying coastal land over a mile from the coast.

What does a tsunami look like when it reaches shore?
Normally, a tsunami appears as a rapidly advancing or receding tide. In some cases, a wall of water or series of breaking waves may form.

How is a tsunami different from a wind-generated wave?
Wind-generated waves usually have periods or time between crests between 5 and 15 seconds. Tsunami periods normally range from 5 to 60 minutes. Also, wind-generated waves break as they shoal and lose energy offshore. Tsunamis act more like a flooding wave. A twenty foot tsunami is a twenty foot rise in sea level.

What are nature's signs that a tsunami may be imminent?
There are a few signs like hard ground shaking for 20+ seconds near the coast or a sudden sea level withdrawal. Tsunamis may be accompanied by loud, booming noises.

Can earthquakes and tsunamis be predicted?
No, earthquakes cannot be predicted. Once an earthquake has occurred, the arrival time of a tsunami, if generated, can be determined accurately. There is not normally enough time to accurately predict tsunami heights near the source. Away from the source, tsunami wave heights can be estimated based on mathematical tsunami models and observed wave heights.

Aerial video of the tsunami that devastated Japan on March 11, 2011.

Click Here to see an animation of an earthquake and the resulting tsunami. It's great for kids, because they get to see how it actually happens!
What are some of the most damaging tsunamis?

Japan: Major tsunami in 2011 generated in the Pacific Ocean.

Asia: Asian tsunami in 2004 generated in the Indian Ocean.

Alaska: Major tsunamis were generated along the Alaskan coast in 1946, 1957, 1958, 1964, and 1965. Many other locally generated tsunamis occurred prior to those dates.

US/Canada West Coast: Tsunamis were generated locally in 1812, 1873, 1878, 1927, 1930, 1946 and 1949. The west coast was also impacted by tsunamis generated in other regions in 1877, 1946, 1952, 1957, 1960, 1964, 1975, 2006, and 2010.

US/Canada Atlantic Coast: Tsunamis were recorded in 1755, 1884, 1886, and 1929.

Puerto Rico and the Virgin Islands experienced damaging tsunamis in 1867 and 1918.

Click Here for the NOAA/National Geophysical Data Center tsunami catalog.

TSUNAMI WARNING- A tsunami warning indicates that a tsunami may be imminent and that coastal locations in the warned area should prepare for flooding. The initial warning is typically based solely on seismic information. After the tsunami is recorded on sea level gages, the warning will be cancelled, restricted, expanded, or downgraded to an advisory. Warnings indicate that flooding up to the maximum expected limit is possible and residents should follow their local emergency management instructions. Warnings are issued when the earthquake information or tsunami forecasts indicate that a wave over 1 meter in amplitude is expected, possible, or ongoing.

TSUNAMI ADVISORY- A tsunami advisory indicates a tsunami which may produce strong currents and is dangerous to those in or very near the water is expected. Large inundations are not expected in areas under advisory status. Advisories will be cancelled, extended, or upgraded to a warning depending on the event severity. Advisories are issued when the tsunami forecast is in the range of 0.3 to 1 meter, or an observed tsunami is in the range of 0.5 to 1.0 meters.

TSUNAMI WATCH- A tsunami watch is an early alert issued to areas which may later be impacted by a tsunami. Tsunami impact is normally at least three hours away for regions within a tsunami watch. The watch will either be upgraded to a warning or advisory in subsequent messages or cancelled depending on the severity of the tsunami. People within a watch area should stay alert for further information regarding tsunami threat.

CREST - The top of a wave.

FJORD - A narrow sea inlet between cliffs or steep slopes.

SURGE - A large wave or billow.

TROUGH - The lowest point between waves.

Click Here to get the latest tsunami warning information from the NWS.

PLAN FOR A TSUNAMI: Have a disaster plan. Know whether you're at risk for danger. Plan an evacuation route. Prepare a disaster supplies kit for your home and car. Include a first aid kit, canned food and a can opener, bottled water, battery-operated radio, flashlight, protective clothing and written instructions on how to turn off electricity, gas, and water.

DURING A TSUNAMI: Follow the instructions issued by local authorities. You will probably want to evacuate immediately. Get to higher ground and as far inland as you can.

AFTER A TSUNAMI: Help injured or trapped people. Stay out of a building if water remains around it. Tsunami waters can cause buildings to sink, floors to crack, or walls to collapse. When re-entering homes, use extreme caution. Check for gas leaks. Open windows and doors to help dry things out. Look for fire hazards.

Lesson Plan: Here is a great lesson plan on learning about tsunamis. Note: This is a PDF file, so you need to have Adobe Acrobat Reader.

Lesson Plan: Here is a great lesson plan on tracking a tsunami.

Lesson Plan: Here is a great lesson plan on tsunamis and how they devastating effects they may cause in the world.

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What is a tsunami? A tsunami is a large ocean wave usually caused by an underwater earthquake or a volcanic explosion. Tsunamis are NOT tidal waves. Tidal waves are caused by the forces of the moon, sun, and planets upon the tides, as well as the wind as it moves over the water.

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Kids learn about tsunamis including what causes them such as earthquakes, where they occur, why they are dangerous, and what happens during a tsunami event.

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Introduction
One of the most powerful and feared natural disasters, the large and destructive water wave known as a tsunami can challenge a jet airplane for speed. Near the coast it can beat a three-story building for height. These waves pack enough energy to destroy an entire coastal community in moments. Underwater earthquakes and volcanic eruptions are the most common causes of tsunamis.

The word tsunami is a Japanese word, represented by two characters: tsu, meaning "harbor," and nami, meaning "wave." Although tsunamis are often referred to as tidal waves, this is a misnomer. Tides are generated by the gravitational effects of the moon, sun, and planets. Tsunamis are caused by a sudden or impulsive disturbance that vertically displaces the water column. They are not connected to tides, though the tide level affects the impact a tsunami has as it reaches the shore.

Tsunamis are most commonly generated by underwater earthquakes, which are caused when the seafloor abruptly deforms. The Earth's outer shell is made up of several slowly moving plates. Most earthquakes occur near the plate boundaries as the plates move over, along, or away from each other. Earthquakes release a large amount of energy, and in the ocean the violent shaking of the seafloor displaces the water. If a large earthquake occurs near the surface of the ocean floor, the resulting energy transfer to the water column produces great waves. Most tsunamis result from earthquakes with a magnitude greater than 6.5 on the Richter scale and that occur less than 30 miles (50 kilometers) beneath the seafloor. Volcanic eruptions, landslides, and other great disturbances of the ocean water can also generate tsunamis.

Wave Properties
A tsunami can travel great distances. After the earthquake, volcanic eruption, or other cause, a series of waves spreads over the ocean surface in ever-widening circles. In the deep water, a tsunami has an amplitude, or height, of only about one or two feet (30 to 60 centimeters). A tsunami has a much longer wavelength and period, however, than the wind-generated waves seen at the beach. (The period is the time between the end of one wave and the beginning of another.) While a wind-generated wave might have a length of approximately 500 feet (150 meters) and a period of 10 seconds, a tsunami may be 60 to 120 miles (100 to 200 kilometers) long and have a period ranging from five minutes to more than an hour.

Tsunamis behave like shallow-water waves because the ratio between the depth of the water and the length of the wave is very small. This property of tsunamis relates directly to the tremendous speed they can achieve, because a shallow-water wave travels at speeds related to the depth of the water and the acceleration of gravity. The deeper the water, the faster the wave. Where the ocean is 13,100 feet (4,000 meters) deep, for instance, a tsunami can travel more than 400 miles (640 kilometers) per hour.

The vast length of a tsunami also affects the force it carries. As the wave travels, it loses energy. But the rate of energy loss is inversely proportional to the length of the wave. This means that the longer the wave, the less energy is lost as it travels, and therefore the more energy it still has as it strikes the coastline.

As the wave approaches land, it slows down and its height increases. Because the speed of the wave is proportional to the water depth, as the water becomes more shallow, the speed of the wave diminishes. Closer to shore, bottom friction and turbulence slow the wave even more. The force of a tsunami as it reaches shore is still enormous, and it will continue to travel until its energy is completely dissipated. This means that it may travel inland several hundred feet, carrying with it boats, large rocks, and other heavy debris. The flow of the water back to the sea can also be extremely destructive.

All low-lying coastal areas are vulnerable to tsunamis. Because the waves have very long periods, the danger posed by a tsunami can last several hours. The first wave may not be the largest of the series. Occasionally a wave's trough-the part with the lowest water level-may arrive first, temporarily causing the water to recede and exposing the seafloor. This may attract curious people and fishers to the seafloor right before the crest, or peak, of the wave arrives and drowns those in its path.

Contunico © ZDF Enterprises GmbH, Mainz

Contunico © ZDF Enterprises GmbH, Mainz

The height of a tsunami is very small in deep water, so it is virtually imperceptible on the open sea. However, various national and international warning centers issue bulletins when there is a possibility of a tsunami. Geological agencies may issue an alert if they observe a very powerful underwater earthquake. Meteorologists may report unusual changes in the sea level. Agencies that monitor tsunamis use tide gauges along coasts to detect changes in water level. Instruments deployed on the seafloor can detect changes in water pressure, and deep-sea buoys transmit the readings via satellite. The United States has two regional tsunami warning centers for the Pacific Ocean-one at Palmer, Alaska, and one near Honolulu, Hawaii. The latter also serves as a warning center for 26 countries lining the Pacific. This international system is organized by the United Nations Educational, Scientific, and Cultural Organization (UNESCO). After a catastrophic tsunami occurred in the Indian Ocean in late 2004, UNESCO decided to oversee the creation of a tsunami warning system for the Indian Ocean and eventually the world.

It is not possible to outrun a tsunami, but there are precautions that can be taken to minimize the possible dangers of a tsunami. The generation of a tsunami is rapid, and because of their great speed, the waves can reach shore very quickly. Anyone who is at the beach or near the ocean and feels the Earth shake should immediately move to higher ground, rather than wait for a warning to be issued. It is not safe to return to low-lying ground until an official "all-clear" has been issued. Those who are at sea when a tsunami warning is issued should not return to port. Tsunamis cause rapid changes in water levels and create dangerous currents in harbors and ports.

Historical Tsunamis
The deadliest tsunami in recorded history occurred in the Indian Ocean in December 2004. It was generated by an extremely large earthquake off the northwest coast of the Indonesian island of Sumatra. The tsunami devastated the islands and coasts of more than 10 countries in southern Asia and eastern Africa. The waves washed away entire villages and killed more than 200,000 people. The death toll was the highest in Indonesia, Sri Lanka, India, and Thailand.

Other large tsunamis of recent history include one that ravaged the northwestern coast of Papua New Guinea in 1998, killing more than 2,100 people, and one that occurred in 1976 in the Philippines, killing about 8,000 people. Another major earthquake-generated tsunami took place in Chile in 1960. With a magnitude of 9.5, the earthquake was the largest ever recorded. The tsunami it generated was responsible for about 2,000 deaths along the Chile-Peru coast. After devastating the coastline of South America, the tsunami traveled for 15 hours across the Pacific to Hilo, Hawaii, claiming an additional 61 lives, and for 22 hours to Japan, killing another 122 people. In 1883 the eruptions of the volcano Krakatoa between the islands of Sumatra and Java created a tsunami that killed more than 36,000 people. On March 11, 2011, offshore Japan was hit with the fifth-largest earthquake in the world since 1900. In the aftermath of the quake (first reported as magnitude 8.9, then later revised to magnitude 9.0), a huge tsunami was created. The earthquake and ensuing tsunami killed thousands of people and left countless others without power and services. ( See also earthquake; flood; volcano.)

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Introduction One of the most powerful and feared natural disasters, the large and destructive water wave known as a tsunami can challenge a jet airplane for speed. Near the coast it can beat a three-story building for height. These waves pack enough energy to destroy an entire coastal community in moments.

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Tsunami is a Japanese word that means "harbor wave." It is a large wave caused by movements in Earth's outer layer, or crust, which move ocean water. For example, an earthquake or a volcano in the ocean could cause a tsunami.

Earth's crust is made up of pieces called tectonic plates. An earthquake happens when these plates push against each other so hard that one of them slips or breaks. Imagine leaning against a friend. If you push against each other harder and harder, one or both of you will fall over. When Earth's plates push against each other, they can move a lot.

If an earthquake happens in the ocean, a large piece of Earth's crust can be thrust upward or slip from side to side. The movement of a large chunk of Earth displaces the water above it, meaning it takes up the space where the water used to be. So where does the water go? It ripples out from the earthquake in waves.

This can also happen if a volcano erupts in the ocean. The lava flowing out of the volcano displaces the water around it. That water can turn into a large wave.

If the earthquake or volcano is very big, then the wave can be very big, too. Big tsunamis usually begin in the deep ocean, where a large volume of water can be displaced. As the wave moves closer to the shore, it grows taller as the ocean becomes shallower. If the water recedes-or moves away from the coast-after an earthquake, a big tsunami may be on its way.

Tsunamis can be hundreds of feet tall, and they travel very fast. This means they can be dangerous even for people who aren't on the beach. Tsunamis can be extremely destructive and can knock down whole buildings.

But not all earthquakes or volcanic eruptions cause tsunamis. Whether a tsunami forms can depend on a lot of things. The shape of the ocean floor can determine if a tsunami happens. So can the distance and direction of the earthquake.

If there's a chance a tsunami is on its way, you don't want to be near the coast. So how can we tell if a tsunami is coming? We use satellites!

MISR (the Multi-angle Imaging SpectroRadiometer) is a NASA tool that watches for tsunamis from space. It has nine cameras, all pointed in slightly different directions. As the satellite passes overhead, it takes nine pictures of the same spot from different angles.

MISR can see sunlight reflecting off ripples and waves. Satellites that look straight down cannot see these ripples.

These images help scientists understand how tsunamis work. The more we learn about tsunamis, the better we can predict where, when and how strong a tsunami will be. That way, people can have enough warning to get away and stay safe.

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A tsunami is a large wave caused by movements in Earth''s outer layer, or crust. Learn more about these big waves and how NASA monitors them.

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Words to Know Am I at Risk? What Can I Do? Learn More

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Rain is pouring hard and fast-more than eight inches in just an hour, turning river water brown with mud. Earthworms wiggle up to the ground as the soil becomes too wet for them. A flood might be coming.

Just about any place on Earth can experience flooding. When so much rain falls that the ground can't absorb it or waterways can't hold it, the overflowing water becomes a destructive force. In the United States, flooding causes more death and damage than tornadoes, hurricanes, or lightning.

How floods develop

During a rainstorm, precipitation-or the water that comes from rain or snow-goes to different places. Some of it flows into streams, lakes, or city water systems. Other precipitation evaporates and returns to the atmosphere.

But much of the rainwater is absorbed by soil. It flows through the top layer of the ground, to plant roots below the surface. This helps provides plants with the water and nutrients they need to grow. The excess water moves deeper into the ground through layers of dirt and rocks where until it becomes part of natural underground wells called groundwater.

A habitat can naturally absorb a healthy amount of rainfall it needs to thrive. But too much rain can cause lake and river levels to rise and overflow their banks, or the soil to become too wet to absorb more water. And though you might think extremely dry habitats would welcome too much rain, it turns out that the parched dirt can't absorb the rain fast enough to capture it all.

Severe coastal storms, quickly melting ice and snow, and collapsed barriers (like concrete dams) can also cause floods. Even damaged beaver dams can lead to an overflow of water that the surrounding earth can't absorb.

Different types of floods

Floods can form slowly over several days or overwhelm an area with little warning. How quickly a flood forms often depends on the habitat.

Slow-forming river flooding happens in regions called floodplains. These are large, flat areas of land along waterways with very shallow banks. When big storms hit, the water overflows the banks and spreads out across the plains.

This type of flooding isn't always bad. It brings nutrients to the surrounding soil, making it fertile for growing crops. That's why many people live in or near floodplains.

But too much water can destroy crops and damage homes. Rushing water can disrupt ecosystems by moving aquatic plants and animals to other habitats. And if flooding is so severe that it flows into local water treatment facilities, experts must monitor the incoming water to make sure the water is safe.

Another type of flooding is called a flash flood, when a flood happens within six hours of a heavy rainfall-as much as eight inches an hour. With no place to go, the moving water will tear through highways, valleys, and canyons, washing away vehicles, roads, bridges, and houses.

Quickly melting ice and snow can also cause flash flooding, especially when mountain snowmelt overflows the waterways below. On coastlines, hurricane rains cause water levels to rise, and the high winds push that water onto land. Called a storm surge, this also causes flash flooding.

Flooding in the future

Scientists believe that warming temperatures caused by climate change are increasing the risk of floods all over the world, especially in coastal and low-lying areas.

Warmer water changes the patterns of ocean currents, which changes global weather patterns. This means that some places will receive more rainfall than the ground can absorb. Other places will get less rain so the land will be drier-and unable to handle rainfall when it does occur.

Scientists think that climate change could also cause stronger hurricanes, with more rain and higher winds causing bigger storm surges. A warmer climate could also mean more snowmelt overwhelming the soil; melting polar ice could cause sea levels to rise and increase flooding. ( Find out how you can help slow climate change.)

How to survive a flood

Experts might issue a flash flood watch if weather conditions are right. It doesn't mean flooding will happen but that meteorologists want people to be prepared. When experts are sure a flash flood is on the way, they issue a warning so people can evacuate immediately. Here's how to keep you and your family safe.

Before a flood
* Know your neighborhood. Research how close you are to streams, drainage channels, canyons, and any other low-lying areas that might flood.
* Keep emergency contact phone numbers in one place so you can get in touch with family members.
* Put together an evacuation plan and share it with everyone in your household. Know what paths and routes you can use to quickly get to a high, dry place.
* Conduct flood drills to practice evacuating quickly.
* Maintain an emergency kit with a three-day supply of food and water. Experts recommend canned or dried foods that don't need to be cooked, and at least one gallon of water per day for each person and pet.

During a flood
* Never wait for orders to leave; if you think a flood might be coming, evacuate immediately.
* If flooding hasn't started, move important items to upper floors of your house.
* If flooding has already started where you are, move to the highest place you can find, like a roof of a house or car. Bring as much food, water, and sheltering blankets as possible.
* Never walk through flood water, especially if it's moving. Hazardous chemicals, sewage, and even wild animals are often in floodwater, and just six inches of moving water can knock you off your feet.
* If you must walk through water to escape, walk where the water is still. Never touch electrical equipment if you are standing in water, or even if you're wet.
* If water is quickly rising while you're in your car, leave your vehicle and move to higher ground, like a hill or bridge.

After a flood
* If you've evacuated your house, return only after you're given the all-clear from officials.
* If you stayed put, check your house for damage to electrical systems and appliances. Get rid of any food that might be contaminated from floodwater (or because it's been unrefrigerated for awhile).
* Check your home for wild animals, especially snakes. They can get washed into your home with the floodwater.
* Ask an adult before you use water to brush your teeth, make food, or even wash your hands. Flooding can contaminate water and make you sick.
Learn more about floods at National Geographic.
Flood safety tips from the Nat Geo Kids book Extreme Weather by Thomas Kostigen

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Learn about what causes flooding, different types of floods-and how to stay safe.

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Most often flooding is caused by heavy rains over a long period of time. After a lot of rain, the ground becomes full of water, and new rainwater runs off, or flows downhill. That runoff goes directly into streams and rivers. In springtime the rain may be combined with melting snow. Because of the extra water flowing into the streams and rivers, their water level rises. If the level rises so much that the water overflows the banks, a flood occurs.

Flooding can be worse if there is not much vegetation (trees, grass, and other plants) on the land around rivers. In general, land that has little vegetation is less able to absorb water. The result is a larger amount of water entering a river system.

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When water overflows onto dry land, a flood takes place. Floods have always been a part of life on Earth. Almost every culture has a legend about a great flood. Since ancient...

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Flooding is when a lot of water overflows onto land that is normally dry. It is the most common natural-weather event. Flooding can happen during heavy rains, when rivers overflow, when ocean waves come on the shore, when snow melts too fast, or when dams or levees break. Flooding may be only a few inches of water, or it may cover a house to the rooftop. Floods that happen very quickly are called flash floods. Floods can cause power outages, disrupt transportation, damage buildings, and create landslides.

Words to Know

Am I at Risk?

What Can I Do?

Before

During

After

Learn More

Did you know?

Flooding can wash out walkways, roads, and fields, making them impossible to detect under flood water. Do not walk or ride in a car through water. It might be deeper than you think! A foot of water can sweep a vehicle off the road. Stay away from moving water!

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Words to Know Am I at Risk? What Can I Do? Learn More

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What is a drought?
A drought is when there is a lack of precipitation over an extended period of time, usually a season or more, resulting in a water shortage for some activity, group, or environmental sector. Its impacts result from the interplay between the natural event (less precipitation than expected) and the demand people place on water supply, and human activities can exacerbate the impacts of drought.

What causes a drought?
Drought has many causes. It can be caused by not receiving rain or snow over a period of time. If you live in a place where most of the water you use comes from a river, a drought in your area can be caused by places upstream from you not receiving enough moisture. There would be less water in the river for you and other people who live along the river to use. People can also play a big role in drought. If we use too much water during times of normal rainfall, we might not have enough water when a drought happens.

Can scientists predict if a drought is going to happen?
No! Studies conducted over the past century have shown that meteorological drought is never the result of a single cause. It is the result of many causes including, global weather patterns, high pressure, the tropical outlook and other global-scale variables.

Are there places in the United States that experience drought?
Yes! The Western United States is experiencing an exceptional and extreme drought at this time. To see the map, Click Here to see the current U.S. Drought Monitor.

What was the Dust Bowl?
Of all the droughts that have occurred in the United States, the drought events of the 1930s are widely considered to be the "drought of record" for the nation. The 1930s drought is often referred to as if it were one episode, but it was actually several distinct events occurring in such rapid succession that affected regions were not able to recover adequately before another drought began. The term Dust Bowl was coined in 1935 to describe the drought-affected south central United States in the aftermath of horrific dust storms. Although it technically refers to the western third of Kansas, southeastern Colorado, the Oklahoma Panhandle, the northern two-thirds of the Texas Panhandle, and northeastern New Mexico, the Dust Bowl has come to symbolize the hardships of the entire nation during the 1930s.

How bad was the drought in the Dust Bowl years?
In the 1930s, drought covered virtually the entire Plains for almost a decade. The drought's direct effect is most often remembered as agricultural. Many crops were damaged by deficient rainfall, high temperatures, and high winds, as well as insect infestations and dust storms that accompanied these conditions. The resulting agricultural depression contributed to the Great Depression's bank closures, business losses, increased unemployment, and other physical and emotional hardships. Although records focus on other problems, the lack of precipitation would also have affected wildlife and plant life, and would have created water shortages for domestic needs.

What was the Black Sunday Dust Storm?
The 1930s were times of tremendous hardship on the Great Plains. Settlers dealt not only with the Great Depression, but also with years of drought that plunged an already-suffering society into an onslaught of relentless dust storms for days and months on end. They were known as dirt storms, sand storms, black blizzards, and "dusters." It seemed as if it could get no worse, but on Sunday, the 14th of April 1935, it got worse. The day is known in history as "Black Sunday," when a mountain of blackness swept across the High Plains and instantly turned a warm, sunny afternoon into a horrible blackness that was darker than the darkest night. Famous songs were written about it, and on the following day, the world would hear the region referred to for the first time as "The Dust Bowl."

How does a drought affect our lives?
Drought affects our lives in many different ways because water is such an important part of so many of our activities. We need water to live, and animals and plants do too. We need water to grow the food we eat. We also use water for many different things in our lives, like washing dishes, cooking, bathing, and swimming or river rafting. Water is also used to help make the electricity we use to run the lights in our houses and the video games you may like to play. When we don't have enough water for these activities because of a drought, many people and many different things will be affected in many different ways.

How can we help if we're in a drought?
One of the easiest steps we can take to help mitigate the impacts of drought is conserving water. If we use water wisely at all times, more water will be available to us and to plants and wildlife when a drought happens. We can lose a lot of water doing simple everyday tasks. Did you know that turning off the water while you brush your teeth can save more than 100 gallons of water a month? If you have a leaky faucet, the drips can add up to 300 gallons of wasted water a month.

What are the different types of drought?
There are four basic approaches to measuring drought: meteorological, hydrological, agricultural, and socioeconomic. The first three approaches deal with ways to measure drought as a physical phenomenon. The last deals with drought in terms of supply and demand, tracking the effects of water shortfall as it ripples through socioeconomic systems.

Meteorological drought is defined usually on the basis of the degree of dryness (in comparison to some "normal" or average amount) and the duration of the dry period. Definitions of meteorological drought must be considered as region specific since the atmospheric conditions that result in deficiencies of precipitation are highly variable from region to region. For example, some definitions of meteorological drought identify periods of drought on the basis of the number of days with precipitation less than some specified threshold. This measure is only appropriate for regions characterized by a year-round precipitation regime such as a tropical rainforest, humid subtropical climate, or humid mid-latitude climate.

Agricultural drought links various characteristics of meteorological (or hydrological) drought to agricultural impacts, focusing on precipitation shortages, differences between actual and potential evapotranspiration, soil water deficits, reduced groundwater or reservoir levels, and so forth. Plant water demand depends on prevailing weather conditions, biological characteristics of the specific plant, its stage of growth, and the physical and biological properties of the soil. A good definition of agricultural drought should be able to account for the variable susceptibility of crops during different stages of crop development, from emergence to maturity.

Hydrological drought is associated with the effects of periods of precipitation (including snowfall) shortfalls on surface or subsurface water supply (i.e., streamflow, reservoir and lake levels, groundwater). The frequency and severity of hydrological drought is often defined on a watershed or river basin scale. Although all droughts originate with a deficiency of precipitation, hydrologists are more concerned with how this deficiency plays out through the hydrologic system. Hydrological droughts are usually out of phase with or lag the occurrence of meteorological and agricultural droughts. It takes longer for precipitation deficiencies to show up in components of the hydrological system such as soil moisture, streamflow, and groundwater and reservoir levels. As a result, these impacts are out of phase with impacts in other economic sectors.

Socioeconomic definitions of drought associate the supply and demand of some economic good with elements of meteorological, hydrological, and agricultural drought. It differs from the aforementioned types of drought because its occurrence depends on the time and space processes of supply and demand to identify or classify droughts. The supply of many economic goods, such as water, forage, food grains, fish, and hydroelectric power, depends on weather. Because of the natural variability of climate, water supply is ample in some years but unable to meet human and environmental needs in other years. Socioeconomic drought occurs when the demand for an economic good exceeds supply as a result of a weather-related shortfall in water supply.

Aquifer - an area that contains large amounts of water under the surface of the earth.

Climate - day-to-day weather over a longer period of time. Climatology is the study of climate.

Climograph - a graph that shows monthly average temperature and precipitation for some location.

Dam - a structure built across a river to hold back water for a variety of reasons, including protecting areas from floods, storing water, and generating power.

Desalination - the process of removing salts and other minerals from seawater so that it can be used for drinking water.

Drought - less rainfall than is expected over an extended period of time, usually several months or longer. Or, more formally, it is a deficiency of rainfall over a period of time, resulting in a water shortage for some activity, group, or environmental sector.

Drought Index - a numerical scale that scientists use to describe the severity of a drought. Scientists take many kinds of data (like streamflow, rainfall, temperature, and snowpack) and "blend" it into a single number, called a drought index value, to make it easier to understand the drought conditions of a particular area. Drought indices are one type of drought indicator.

Drought I ndicator - a way to look at one or more variables, such as precipitation, to describe available water in soil or hydrologic systems. It may be a record of a single measurement, such as rainfall at a particular rain gauge. It may also be a complex index. Drought indices (indexes) are a subset of drought indicators.

Dust Bowl - an area of the U.S. Plains that included parts of Kansas, Colorado, Oklahoma, Texas, and New Mexico. The term was coined in the 1930s, when dry weather and high winds caused many dust storms throughout the United States, but particularly in this area.

Erosion - a process that wears the earth's surface away, causing soil to move from one place to another. It's a natural process, but human activities can make it worse.

Groundwater - water that is found underground in spaces in soil, sand, or rocks.

Hydroelectricity - electricity created by channeling water through turbines in power stations located below dams.

Irrigation - an agricultural practice that involves providing water to crops through pipes, ditches, or streams.

Mitigation - actions that we can take before, or at the beginning of, drought to help reduce the impacts of drought. Mitigation includes actions as diverse as drought planning, implementing land use practices that increase the organic content and water-holding capacity of soil, and designing agricultural policy that doesn't encourage short-term economic gains at the expense of long-term productive capacity. The Intergovernmental Panel on Climate Change uses mitigation to mean reducing emissions of greenhouse gasses.

Reservoirs - water that's collected and stored in natural or manmade lakes.

Submarginal Farmland - lands with nutrient-poor soils and/or soils that have been damaged by poor cultivation practices.

Water Banking - a water management strategy that temporarily transfers water from those who are willing to lease it to those who are willing to pay to use it.

Water Recycling - reusing treated wastewater for purposes like agricultural and landscape irrigation. It's also referred to as water reclamation or water reuse.

Xeriscaping - a type of landscaping around homes and businesses that uses a limited amount of water.

Click on the chart to make larger!

Click Here to see the current U.S. Drought Monitor!

Lesson Plan: Here is a lesson plan on water conservation.

Lesson Plan: Here is a lesson plan on how drought affect agriculture.

Science Fair Project Ideas: Here is a complete list of science fair project ideas. Discover the science behind the weather that impacts us every day.

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What is a drought? A drought is when there is a lack of precipitation over an extended period of time, usually a season or more, resulting in a water shortage for some activity, group, or environmental sector.

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A flood is an overflow of water on normally dry ground. This is most commonly due to an overflowing river, a dam break, snowmelt, or heavy rainfall. Less commonly happening are tsunamis, storm surge.

The most deadly flooding was in 1931 in China and killed between 2,000,000 and 4,000,000 people. The Kerala flood in India was another flood that has destroyed people's houses.

During a flood, people try to move themselves and their most precious belongings to higher ground quickly. The process of leaving homes in search of a safe place is called flood evacuation.

Bangladesh is the most flood prone area in the world.

Pollution of drinking water

During a flood there is plenty of water logging and overflow of water, but it is mostly polluted and not safe to drink. If people drink this dirty water, they may suffer from diseases such as typhoid and cholera, hepatitis and other such diseases. People can get ready to survive a flood by filling many containers with fresh and clean drinking water and storing other emergency supplies; like: medicine and food. During flood people try to go to higher sides because the flood water wouldn't reach high areas. Also drains overflow and mix with clean water and people who drink it might fall ill.

Floods can happen on flat or low-lying areas when water is supplied by rainfall or snowmelt more rapidly than it can either infiltrate or run off. The excess accumulates in place, sometimes to hazardous depths. Surface soil can become saturated, which effectively stops infiltration, where the water table is shallow, such as a floodplain, or from intense rain from one or a series of storms. Infiltration also is slow to negligible through frozen ground, rock, concrete, paving, or roofs. Areal flooding begins in flat areas like floodplains and in local depressions not connected to a stream channel, because the velocity of overland flow depends on the surface slope. Endorheic basins may experience areal flooding during periods when precipitation exceeds evaporation.

Riverine (Channel)

Floods occur in all types of river and stream channels, from the smallest ephemeral streams in humid zones to normally-dry channels in arid climates to the world's largest rivers. When overland flow occurs on tilled fields, it can result in a muddy flood where sediments are picked up by run off and carried as suspended matter or bed load. Localized flooding may be caused or exacerbated by drainage obstructions such as landslides, ice, debris, or beaver dams.

Slow-rising floods most commonly occur in large rivers with large catchment areas. The increase in flow may be the result of sustained rainfall, rapid snow melt, monsoons, or tropical cyclones. However, large rivers may have rapid flooding events in areas with dry climate, since they may have large basins but small river channels and rainfall can be very intense in smaller areas of those basins.

Rapid flooding events, including flash floods, more often occur on smaller rivers, rivers with steep valleys, rivers that flow for much of their length over impermeable terrain, or normally-dry channels. The cause may be localized convective precipitation (intense thunderstorms) or sudden release from an upstream impoundment created behind a dam, landslide, or glacier.

Flash floods are the most common flood type in normally-dry channels in arid zones, known as arroyos in the southwest United States and many other names elsewhere. In that setting, the first flood water to arrive is depleted as it wets the sandy stream bed. The leading edge of the flood thus advances more slowly than later and higher flows. As a result, the rising limb of the hydrograph becomes ever quicker as the flood moves downstream, until the flow rate is so great that the depletion by wetting soil becomes insignificant.

Estuarine and coastal

Flooding in estuaries is commonly caused by a combination of storm surges caused by winds and low barometric pressure and large waves meeting high upstream river flows.

Coastal areas may be flooded by storm surges combining with high tides and large wave events at sea, resulting in waves over-topping flood defenses or in severe cases by tsunami or tropical cyclones. A storm surge, from either a tropical cyclone or an extratropical cyclone, falls within this category. Research from the NHC (National Hurricane Center) explains: "Storm surge is an additional rise of water generated by a storm, over and above the predicted astronomical tides. Storm surge should not be confused with storm tide, which is defined as the water level rise due to the combination of storm surge and the astronomical tide. This rise in water level can cause extreme flooding in coastal areas particularly when storm surge coincides with spring tide, resulting in storm tides reaching up to 20 feet or more in some cases."

Urban flooding

Catastrophic

Catastrophic riverine flooding is usually associated with major infrastructure failures such as the collapse of a dam, but they may also be caused by drainage channel modification from a landslide, earthquake or volcanic eruption. Examples include outburst floods and lahars. Tsunamis can cause catastrophic coastal flooding, most commonly resulting from undersea earthquakes.

Causes of floods

Flooding is usually caused when a volume of water within a water body, such as a lake, overflows outside it. Sometimes if a dam breaks, it suddenly releases a large amount of water. The result is that some of the water travels to land, and 'floods' the area. Many rivers are in a channel, between river banks. They flood when the strength of the river causes it to flow beyond the banks. This is more common at bends or meanders.

Flood damage can be prevented by moving away from places that flood. However, people have long liked to have their homes and businesses alongside water because water is good for agriculture and transport and in other ways. Floods are also caused due to improper management of drains.

Rainfall is the most common cause. Snow melt is also a cause of flooding. Tsunamis and Storm Surge are less common ways that floods happen. Coastal Flooding is another common cause of flooding, and this is caused by low pressure systems or storms.

Flood safety planning

In the United States, the National Weather Service gives out the advice "Turn Around, Don't Drown" for floods; that is, it recommends that people get out of the area of a flood, rather than trying to cross it. At the most basic level, the best defense against floods is to seek higher ground for high-value uses while balancing the foreseeable risks with the benefits of occupying flood hazard zones. Critical community-safety facilities, such as hospitals, emergency-operations centers, and police, fire, and rescue services, should be built in areas least at risk of flooding. Structures, such as bridges, that must unavoidably be in flood hazard areas should be designed to withstand flooding. Areas most at risk for flooding could be put to valuable uses that could be abandoned temporarily as people retreat to safer areas when a flood is imminent.

Planning for flood safety involves many aspects of analysis and engineering, including:

observation of previous and present flood heights and inundated areas,

statistical, hydrologic, and hydraulic model analyses,

mapping inundated areas and flood heights for future flood scenarios,

long-term land use planning and regulation,

engineering design and construction of structures to control or withstand flooding,

intermediate-term monitoring, forecasting, and emergency-response planning, and

short-term monitoring, warning, and response operations.

Each topic presents distinct yet related questions with varying scope and scale in time, space, and the people involved. Attempts to understand and manage the mechanisms at work in floodplains have been made for at least six millennia.

In the United States, the Association of State Floodplain Managers works to promote education, policies, and activities that mitigate current and future losses, costs, and human suffering caused by flooding and to protect the natural and beneficial functions of floodplains - all without causing adverse impacts. A portfolio of best practice examples for disaster mitigation in the United States is available from the Federal Emergency Management Agency.

In many countries around the world, waterways prone to floods are often carefully managed. Defenses such as detention basins, levees, bunds, reservoirs, and weirs are used to prevent waterways from overflowing their banks. When these defenses fail, emergency measures such as sandbags or portable inflatable tubes are often used to try to stem flooding. Coastal flooding has been addressed in portions of Europe and the Americas with coastal defenses, such as sea walls, beach nourishment, and barrier islands.

In the riparian zone near rivers and streams, erosion control measures can be taken to try to slow down or reverse the natural forces that cause many waterways to meander over long periods of time. Flood controls, such as dams, can be built and maintained over time to try to reduce the occurrence and severity of floods as well. In the United States, the U.S. Army Corps of Engineers maintains a network of such flood control dams.

In areas prone to urban flooding, one solution is the repair and expansion of man-made sewer systems and stormwater infrastructure. Another strategy is to reduce impervious surfaces in streets, parking lots and buildings through natural drainage channels, porous paving, and wetlands (collectively known as green infrastructure or sustainable urban drainage systems (SUDS)). Areas identified as flood-prone can be converted into parks and playgrounds that can tolerate occasional flooding. Ordinances can be adopted to require developers to retain stormwater on site and require buildings to be elevated, protected by floodwalls and levees, or designed to withstand temporary inundation. Property owners can also invest in solutions themselves, such as re-landscaping their property to take the flow of water away from their building and installing rain barrels, sump pumps, and check valves.

In some areas, the presence of certain species (such as beavers) can be beneficial for flood control reasons. Beavers build and maintain beaver dams which will reduce the height of flood waves moving down the river (during periods of heavy rains), and will reduce or eliminate damage to human structures, at the cost of minor flooding near the dams (often on farmland). Besides this, they also boost wildlife populations and filter pollutants (manure, fertilisers, slurry). UK environment minister Rebecca Pow stated that in the future the beavers could be considered a "public good" and landowners would be paid to have them on their land.

Related pages

Images for kids

A dog sitting on top of 2 feet of mud deposited by flooding in the 2018 Kerala floods in India. Flooding not only creates water damage, but can also deposit large amounts of sediment.

Minor flooding in a parking lot off Juniper street Atlanta on Christmas Eve from thunderstorms caused by an El Nino event. The same El Nino caused recorded highs for January in Atlanta

Flash flooding caused by heavy rain falling in a short amount of time.

Dozens of villages were inundated when rain pushed the rivers of northwestern Bangladesh over their banks in early October 2005. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Terra satellite captured the top image of the flooded Ghaghat and Atrai Rivers on October 12, 2005. The deep blue of the rivers is spread across the countryside in the flood image.

In Spanish: Inundación para niños

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Information for kids K - 6 about floods, how they occur and their effects. Includes easy to read section for early readers. For school and homeschooling projects and to read for interest.

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Did you know fires move faster when traveling uphill? Explore these interesting wildfire facts for kids from the experts at the Western Fire Chiefs Association (WFCA).

A wildfire is an uncontrolled fire that starts burning in wildland, such as a forest, grassland, or the edge of an urban area. Firefighters focus on protecting human lives, structures, and resources when they battle wildfires. ¹ Learn some wild facts about wildfires and remember: always be careful with fire.

Fact #1

Humans cause 89% of annual wildfires.²

Most wildfires are caused by humans and can result from many kinds of activities. For example, a stray ember from a campfire can spark a blaze, or a spark from a car engine can ignite dry grass. Not all human-caused fires are accidental. Starting a fire on purpose, to hurt the environment, buildings, or people, is called arson. Arson is against the law and can have terrible consequences.

Sometimes, firefighters will very carefully light fires on purpose in order to clear overgrown plants and help nature thrive. ³ However, these burns are handled by professionals in controlled conditions. A wildfire, on the other hand, is unplanned and extremely dangerous. Even if fires start small, it is difficult to predict if they will become large, destructive wildfires that threaten human lives and communities.

Fact #2

You need three things for a fire to start: heat, oxygen, and a fuel source.

Firefighters call heat, air, and fuel the fire triangle. These three things combined can create ignition and start a fire. ⁴ Sources of heat can be cigarettes, a spark from a campfire or a gas-powered tool like a chainsaw, or even the sun. Fuel can be the dry wood you use to make a campfire, or it can be plants and grasses. Dry weather, especially droughts, and windy days make wildfires more likely and more dangerous.

Fact #3

Wildfires move at an average of 14 miles per hour.

The speed of a wildfire varies depending on the terrain, the type of fuel available, and weather conditions. ⁵ Rising smoke and heat can dry out fuel further up the slope of a hill, so fire burns more quickly uphill. Wildfires can also quickly get out of control when flames move from the ground to the tops of trees.

Fact #4

Wildfires can happen anywhere in the United States.

Wildfires happen more frequently in the central U.S. and on the East Coast, but wildfires that happen in the Western states (Alaska, Arizona, California, Colorado, Idaho, Montana, New Mexico, Nevada, Oregon, Utah, Washington, and Wyoming) are larger. Many Western state fires happen in undeveloped areas and tend to burn more acres than wildfires in other parts of the U.S. ²

Fact #5

Wildfires burn 5-10 million acres in the United States every year.

In the U.S., there has been a 223% increase in the amount of land burned by wildfires annually since 1983, when official wildfire record-keeping began. Wildfires in 1983 burned 1.3 million acres of land; in 2021, there were 7.1 million acres burned by wildfires. ⁶

Fact #6

Lightning is the biggest natural cause of wildfires.

There are two types of lightning: cold and hot. Cold lightning has an intense electrical current but does not last very long and rarely starts fires. Hot lighting has a weaker electrical current, but the bolt of lightning stays for a longer period of time. These longer-lasting bolts can cause wildfires. 7 Even though humans cause most wildfires, fires started by lightning are usually larger and burn more land. ²

Fact #7

Wildfires can take many shapes-even tornados!

Wildfires move, spread, and grow in several different ways.

Ground fires burn dead plant debris from the forest floor. These fires can burn for a long time without being detected because they burn so slowly and produce very little smoke. They can even burn through tree roots.

Surface fires happen when a fire burns slowly across a forest floor. This type of fire kills living vegetation and tree saplings.

Crown fires happen when winds, or fuel sources like vines, bring fire to the tops of trees. This type of fire spreads fast as the wind blows flames from treetop to treetop.⁸

Tornado fires are an extreme fire behavior. They are created by air temperature shifts and wind current changes. Flames can burn inside or outside of the tornado. These types of fires can grow very quickly.⁹

Fact #8

Fire is part of the ecosystem and helps maintain forests.

Fire is essential for the health of wildlands, just like rain and snow have their place in the natural cycle. It can even help certain trees spread their seeds. Giant sequoias are the largest trees on Earth, but they need fire in order to spread. Fire makes space in the forest for more light and water to reach sequoia seedlings. The mature trees are sturdy enough to withstand smaller, more frequent wildfires, and the heat from fires opens the cones to release sequoia seeds. ¹⁰ Firefighting in wild areas now includes regular, controlled burns that clear debris and potential fuel from the landscape. This work ensures that fire can benefit the environment while being safely managed. ¹

Fact #9

Extreme wind patterns cause wildfires to spread and grow rapidly.

The Rocky Mountains run from New Mexico to Canada. This huge mountain range creates strong wind currents. These winds are called Santa Ana winds when they move west towards Southern California ¹¹ and Chinook winds when they move east towards Colorado and Montana. 12 These winds can blow at 60-100 miles per hour and have fanned wildfires to dangerous heights in nearby states in just minutes.

Fact #10

The annual number of wildfires in the United States is decreasing, but the amount of acres burned by wildfires is going up.

Since 2000, wildfires have burned an average of 7 million acres every year-more than double the average amount of acres burned in the 1990s. However, the average number of annual wildfires in the 1990s was 78,600, while the current average number of annual wildfires is 70,000. ²

Sources

1. National Park Service, "Wildland Firefighting Tactics." Accessed December 14, 2022.

2. Congressional Research Service, "Wildfire Statistics." Accessed January 10, 2023.

3. National Park Service, "Types of Wildland Fire." Accessed December 14, 2022.

4. Firetrace, "What are the Different Stages of a Fire?" Accessed December 12, 2022.

5. Mercury Insurance, "How Wildfires Start and Spread." Accesses October 25, 2022.

6. Bankrate, "U.S. Wildfire Statistics 2022." Accessed January 10, 2023.

7. National Park Service, "Wildfire Causes and Evaluations." Accessed January 9, 2023.

8. Northwest Fire Science Consortium, "What are Types of Fire?" Accessed January 11, 2023.

9. Library of Congress, "Can a tornado be made out of fire?" Accessed January 11, 2023.

10. PBS, "Why the Giant Sequoia Needs Fire to Grow." Accessed January 10, 2023.

11. Science, "California's fire-fanning Santa Ana winds may not get any better with climate change." Accessed January 11, 2023.

12. Live Science, "What Are Chinook Winds?" Accessed January 11, 2023.

Related Article

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Did you know fires move faster when traveling uphill? Explore these interesting wildfire facts for kids from the experts at the Western Fire Chiefs Association (WFCA).

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A wildfire, or wildland fire, is an uncontrolled fire in a forest, grassland, brushland, or other sparsely populated area. Terms such as forest fire and brush fire may be used to describe specific types of wildfires. In Australia they are called bushfires.

Wildfires can be catastrophic, and they are often considered to be natural disasters. About 90 percent of them, however, are ignited by people, either by accident or on purpose. Accidental wildfires are started by unattended campfires, discarded cigarettes, or other careless behavior. Intentionally set wildfires are the result of arson. Only 10 percent of wildfires are started by natural causes, such as lightning or lava.

Fire danger in a wildland setting varies with weather conditions. Drought, heat, and wind dry out grass, leaves, and light branches, making them easier to ignite. Fire spreads quickly in these materials, which are known as flash fuels. The burning of flash fuels can create enough heat to ignite heavier fuels such as tree stumps and heavy branches. Once these heavy fuels are burning, it is hard to put the fire out. Green fuels-growing trees and plants-are not considered flammable, but an intense fire can dry out leaves and needles quickly enough to allow them to catch fire. Drought, heat, and wind all increase the intensity of a wildfire. The landscape also affects wildfire, which spreads quickly uphill and slowly downhill.

U.S. Air Force photo by Staff Sgt. Stephany D. Richards/U.S. Department of Agriculture

© University of Melbourne, Victoria, Australia

Tools for fighting wildfires include portable pumps, tank trucks, and earth-moving equipment. Airplanes and helicopters are also very important in fighting wildfires. They are used for dumping water or other chemicals that can slow down or contain wildfires. Aircraft are also used for gathering information and for moving people, supplies, and equipment. Technology has come to play an increasingly important role in combating wildfires. Forest managers and firefighters use satellites to detect fires in their early stages and to track fires in progress. They also use computer models to predict a fire's path.

U.S. Air Force photo by Master Sgt. Jeremy Lock/U.S. Department of Agriculture

Firefighting forces specially trained to deal with wildfires are maintained by public and private owners of forestlands. Such a force may attack a fire directly by spraying water and beating out flames. They may also try to stop the fire from spreading by removing vegetation at the edge of the fire. The cleared strip of land is called a fire line or firebreak. When the edge of the fire is too hot to approach, firefighters create a fire line at a safe distance. Sometimes they use a technique called backfiring, which involves setting controlled fires to eliminate fuel in the path of the wildfire. Backfiring is used only as a last resort.

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A wildfire, or wildland fire, is an uncontrolled fire in a forest, grassland, brushland, or other sparsely populated area. Terms such as forest fire and brush fire may be used to describe specific types of wildfires. In Australia they are called bushfires. Wildfires can be catastrophic, and they are often considered to be natural disasters.

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What is a wildfire?
A wildfire also known as a wildland fire, forest fire, vegetation fire, grass fire, peat fire, bushfire (in Australia), or hill fire is an uncontrolled fire often occurring in wildland areas, but which can also consume houses or agricultural resources. Wildfires often begin unnoticed, but they spread quickly igniting brush, trees and homes.

What causes a wildfire?
Common causes of wildfires include lightning, human carelessness, arson, volcano eruption, and pyroclastic cloud from active volcano. Heat waves, droughts, and cyclical climate changes such as El Niño can also have a dramatic effect on the risk of wildfires. Although, more than four out of every five wildfires are caused by people.

Where can wildfires occur?
Wildfires can occur anywhere, but are common in the forested areas of the United States and Canada. They are also susceptible in many places around the world, including much of the vegetated areas of Australia as well as in the Western Cape of South Africa. The climates are sufficiently moist to allow the growth of trees, but feature extended dry, hot periods. Fires are particularly prevalent in the summer and fall, and during droughts when fallen branches, leaves, and other material can dry out and become highly flammable. Wildfires are also common in grasslands and scrublands.

What are the Santa Ana winds?
The Santa Ana winds are hot, dry winds that aggravate the fire danger in forests and bush lands. These winds characteristically appear in Southern California and Northern Baja California weather during autumn and early winter. In southern California, under the influence of Santa Ana winds, wildfires can move at tremendous speeds, up to 40 miles in a single day, consuming up to 1,000 acres per hour. Dense clouds of burning embers push ahead of the flames crossing firebreaks without a problem.

What is a fire tornado?
A fire tornado or fire whirl is just a tornado made of fire. It happens when certain conditions (depending on air temperature and currents), acquires a vertical vorticity and forms a whirl, or a tornado-like effect. Fire tornadoes may be whirlwinds separated from the flames, either within the burn area or outside it. A fire tornado can make fires more dangerous.

How do firefighters put out the wildfires?
Firefighters use a tool known as a pulaski. Its a combination of an ax and hoe used to dig a fireline. A fireline is a strip of land from which all brush and debris have been cleared to rob a wildfire of its fuel. Firefighters also use hotshots and smoke jumpers to clear a large path in a big circle around the fire so the blaze is contained in a ring of dirt. When the fire reaches this area, it runs out of fuel and starves to death. If the fire is too large, however, planes and helicopters fly overhead, dropping water and special chemicals that smother the flames. This pink, fire-retardant chemical is called sky jell-o.

Click Here to get the latest wildfire information.

Click Here for to get more wildfire information.

Click Here to see if there has been any recent wildfire activity across the U.S.

SURFACE FIRES - The most common type of wildfires, surface fires move slowly and burn along the forest floor, killing and damaging vegetation.

GROUND FIRES - These are usually started by lightning, ground fires burn on or below the forest floor through the root system.

CROWN FIRES - These fires spread by wind moving quickly along the tops of trees.

SANTA ANA WINDS - "Santa Ana" is the name given to the gusty northeast or east wind that occurs in Southern California during the fall and winter months. Santa Ana winds are often hot and very dry, greatly aggravating the fire danger in forests and bush lands.

CONFLAGRATION - A large and destructive fire, typically aggravated by strong winds that carry firebrands over natural or artificial barriers.

Click Here to learn about more wildfire facts!

BEFORE A WILDFIRE: Have a disaster plan. Know whether you're in a wildfire prone area. Plant fire resistant shrubs and trees around your home. Have a garden hose that is long enough to reach around your home. Prepare a disaster supplies kit for your home and car. Include a first aid kit, canned food and a can opener, bottled water, battery-operated radio, flashlight, protective clothing and written instructions on how to turn off electricity, gas, and water. Always listen to the radio and television for the latest information and instructions for your area.

DURING A WILDFIRE: If you're advised to evacuate then do so immediately. Wear protective clothing and lock your home. Tell someone you left and where you are going. Choose a safe route away from fire hazards. Watch for changes in the speed and direction of fire and smoke.

AFTER A WILDFIRE: Stay away from wildfire areas until it is safe.

Lesson Plan: Here is a great lesson plan on teaching students to have an escape plan if a fire threatens their home.

Science Fair Project Ideas: Here is a complete list of science fair project ideas. Discover the science behind the weather that impacts us every day.

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What is a wildfire? A wildfire also known as a wildland fire, forest fire, vegetation fire, grass fire, peat fire, bushfire (in Australia), or hill fire is an uncontrolled fire often occurring in wildland areas, but which can also consume houses or agricultural resources.

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Forest fires are large uncontrolled fires that take place in the forest. Some of the fiercest fires occur in the forest because there is so much fuel (trees) to burn. Forest fires are a type of wildfire. Other types of wildfires include grass fires, brush fires, and hill fires.

Major Causes of Forest Fires

The major cause of forest fires in the United States is human activities. This can be carelessness such as not putting out a campfire or dropping a lit cigarette. It may also be arson, which is setting a fire on purpose and is against the law. Around 80% of forest fires in the United States are caused by humans.

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Kids learn about forest fires including major human and natural causes, how they spread, firefighters, campfire safety, fun facts, and good wildfires.