Changing Earth’s Surface 4.4

How might a natural disaster affect Earth’s surface? It might. change landforms.

How might a fire alter an environment and how can the area benefit from a fire? A fire will burn down trees destroying animal habitats. It can destroy some trees, but will allow for the germination of other trees. Some seeds require intense heat in order to germinate. Some fires prevent larger fires from occurring when the vegetation is drier.

How can environments change? What kinds of natural events cause changes in an ecosystem? Earthquakes Floods Fire Hurricanes Tornadoes Volcanic eruptions

How can organisms change an ecosystem? They could eat too many of one species, enter a new ecosystem, or use too many resources.

Environments are constantly changing. Think about where you live… How has your environment changed since you’ve lived there? Have new trees or plants grown? Have fences been added? Have new houses been built? Things in our environment are change all the time. What has changed outside our school even this year???

Environmental changes can be caused by natural events or by human actions. Natural events include: Earthquakes, storms, volcanoes, droughts, and other natural disasters Natural disasters can happen suddenly and be very violent. Think of an earthquake or a volcanic eruption. These changes greatly affect the plants, animals, and people living where these disasters occur. There is very little that anyone can do to prevent these natural disasters from occurring.

Organisms can cause change in an environment. Beavers are a good example. They build dams which can cause flooding, but the dams can also be beneficial by creating new habitats and food supplies. Large animals such as an elephant can cause damage by trampling trees and seedlings.

Organisms can cause change in an environment (continued) It’s not just land environments that change. Aquatic environments can also change. Algae could rapidly reproduce and use up nutrients and oxygen. Aquatic organisms can build reefs. These can create new habitats for other organisms.

Organisms can cause change in an environment (continued) People can cause change in an environment. Forests are cut down and destroy animals’ habitats to build roads and neighborhoods. People also cause pollution that damages water, soil, and air quality.

Tsunamis What is a tsunami? A tsunami is a series of huge waves caused by an earthquake or volcanic eruption beneath the ocean. Most are started by earthquakes.

How is plate tectonics related to the formation of tsunamis? Plate movement causes the earthquakes and volcanic eruptions that create tsunamis.

December 26, 2004 An earthquake measuring 9.0 and 9.3 on the Richter scale occurred in the Indian Ocean. This triggered a tsunami that sent a series of waves crashing onto the shorelines of southeast Asia. This tsunami destroyed entire villages and killed hundreds of thousands of people.

What causes floods? Usually floods are caused by a large amount of rainfall over a very short period of time. Why are floods dangerous? The force of rapidly moving floodwater can injure people and animals, uproot trees and other vegetation, and destroy or damage homes and property.

How can people prevent a river from flooding? People often build levees and dams in an effort to prevent rivers from overflowing their banks and flooding the surrounding areas. How can floods change the landscape of an area? They can erode the land or deposit large amounts of mud and debris.

Floodwater Floodwater picks up and carries away tons of mud and debris. Once the water recedes, the mud and debris are left behind. This mud and debris can bury crops and other plants, damaging or killing them.

Benefits of a flood A flood can benefit future crops. The mud that is left behind can be nutrient rich and will renew the soil making it more fertile.

Controlling flood waters In areas where floods are likely, people try to control the water’s flow by building dams or levees. A levee is a wall or a large mound of earth built along a river to prevent it from flooding. They raise or extend the banks of the river so that more water than usual can flow in the river.

Levees A levee can be a good solution to flooding, but a levee can also make a river valley narrower. This can cause increased flooding farther downriver.

New Orleans, 2005 In 2005, a break in a levee caused severe flooding in New Orleans.

How do earthquakes and landslides affect habitats? Earthquakes can cause a tremendous amount of damage. Power lines and gas lines can be broken causing fires. Earthquakes can also cause changes in landforms. Large cracks in the ground can open and shifting ground can cause a cliff to form in seconds. It can change a river’s course, drain a lake, or change the appearance of the natural and human-made features of a region.

Landslides A factor that contributes to landslides is the slope of the land. As the angle of the slope increases, the slope becomes too steep to hold rock and soil. Streams can cause slopes to become very steep. As the water from the stream flows through a valley, the water can cut away rock and soil until the valley wall becomes too steep. Waves can also cause slopes to become too steep.

Landslides A landslide can cause more damage than an earthquake. It can carry buildings down a hillside or bury highways under debris. Trees can be uprooted and change a small slope to a steep cliff. Tumbling rocks from the landslide can damage the riverbed by removing plants and killing fish and other animals. Debris can fall into rivers or streams and create dams, change the course of the water, or cause flooding.

What are long-term effects of natural disasters? The sudden changes caused by natural disasters can have long-term effects on Earth and its habitats. A volcanic eruption can send gases and particles of ash into the air. This debris spreads into the atmosphere where it can remain for months or even years.

Natural Disasters can bring positive changes. Volcanoes build new land. Floods and landslides can add to the soil by leaving behind nutrient-rich mud. Volcanic ash can block sunlight from small plants so that surrounding trees grown more quickly. New habitats can be formed and fresh minerals can brought to the Earth’s surface.

How can living things change their environments? Beavers build dams, creating new habitats; elephants can trample trees and seedlings; humans cut down forests and cause pollution.

Can a natural environmental change cause more damage than a change caused by people? Give an example. Yes, a natural ecosystem change can cause more damage than one caused by humans. A volcano, for example, can cause more damage to a local ecosystem than is caused by building a road.

What information would indicate to scientists that a tsunami might be about to occur? An earthquake or volcanic activity as well as changes in wave height and length might indicate to scientists that a tsunami is about to occur.

How do tsunamis damage habitats over a wide area? Tsunamis damage habitats because they crash ashore with a powerful force and submerge large areas of land.

How can floods harm people? Floods can damage homes and other structures, pollute water supplies, and create dangerous situations in which people are suddenly surrounded by water. People and animals can drown.

How can floods affect crops that are planted near a river? Floods can damage or destroy crops that have been planted, but they can also enrich the soil for future planting.

How do earthquakes affect wildlife habitats? Earthquakes cause violent shaking that disturbs animal and plant life. They change the shape of the landscape by opening cracks in the ground and moving waterways.

What might happen if a landslide occurred in a populated area? Buildings, including people’s homes, might be damaged or lost. Roads, power lines, and water-supply lines might be damaged.

How might an area benefit from a volcanic eruption? Wildfires might clear out old plant growth, add nutrients to the soil, and encourage new plants to sprout.

How can a natural disaster affect the climate of an area? A natural disaster can affect the climate by changing the temperature of the air, changing the depth or location of bodies of water, adding gases and particles of ash to the atmosphere, or changing the shape of the Earth’s surface.