Weathering and Erosion

Weathering is the breaking down of Earth’s surface into smaller pieces. EROSION is the process that picks up and carries away these materials. Weathering and Erosion

Sometimes the earth’s surface changes VERY QUICKLY For Example: Earthquakes Landslides Volcanic eruptions Tsunamis Other times, the changes to the earth’s surface occur very SLOWLY This is known as WEATHERING

Weathering Changes the Surface of the Earth “Weathering” is a general term that describes processes that break down rocks at or near the surface. Weathering is the process where rock (the earth’s surface) is dissolved, worn away or broken down into smaller and smaller pieces. There are 3 types: 1. Biological Weathering 2. Physical Weathering 3. Chemical weathering. WEATHERING

What does “Weathered” mean? It means the Earth’s solid surface will gradually be broken into smaller and smaller pieces. It happens all the time; it is a natural action. A LARGE ROCK breaks into pebbles.

Biological Weathering Describes the action of living things on the solid surface of the Earth. Roots of plants “digging” into the rock cause them to break apart. Lichen (fungus) is often found breaking down the surface of the rocks on which it is attached. Burrowing and digging by animals and insects also contribute to this breaking down process.

Tree roots breaking up rock by “digging” into them.

Burrowing of Animals

Plant Roots

Physical Weathering Breaks rocks into smaller pieces When water freezes, it expands. The expansion can break the rock into smaller pieces. The action of wind blowing small pieces of rock against larger rocks wears rock away. The movement of running water in streams and rivers cause rocks to weather

Physical weathering physically breaks up rock. Frost shattered rockFrost shattered brick One example is called frost action or frost shattering. Water gets into cracks and joints in bedrock. When the water freezes it expands and the cracks are opened a little wider Over time pieces of rock can split off a rock and big boulders are broken into smaller rocks and gravel. This process can also break up bricks on buildings.

Frost Wedging

Chemical Weathering Primarily responsible for the formation of soils Carbon dioxide dissolved in rainwater makes a weak acid that dissolves certain rocks such as limestone.

Rain water is a very weak acid. It can dissolve limestone and other low carbonate rocks leaving behind pits and holes.

Water Water weathers some rock by dissolving it

Acid Rain Compounds from burning coal, oil and gas react chemically with water forming acids. Acid rain causes very rapid chemical weathering Weathering Brain Pop

Erosion Weathering causes the solid surface of the Earth to break down, dissolve and decompose. Erosion picks up the pieces and moves them from place to place

Water Wind Ice How does EROSION occur?

Water is the most powerful agent of erosion. Rain water picks up soil and sand as it runs off. Rivers carry away rocks and soils. Over MANY YEARS, rivers move enough materials to create valleys and canyons. Along the coastal areas, the waves along the oceans move sand and rocks. WATER

WIND Wind erosion happens mostly along the ground surface. Wind carries off soil and small rocks You have probably felt the sting of the dirt and sand when it blows against your legs or in your face.

A “wall” of dust approaching a Kansas home during the 1935 Dust Bowl. In the 1930’s, large amounts of soil were lost when areas of the central United States received LITTLE RAIN. Plants died and could no longer anchor the soil when winds blew. This time became known as the “Dust Bowl”. WIND

ICE Snow and ice can form glaciers in the mountains These glaciers move down the mountainside. As they move, they act like bulldozers, picking up rocks and soil and pushing boulders along in front of them.

Erosion is a natural process, but there are ways we can slow it down. 1.Plant cover crops on bare land 2. Plant trees to slow the speed of the wind 3. Build terraces, raised rows of dirt in the fields to help slow the run off of the rain.

Erosion is considered to be an environmental problem in many parts of the world. What do you think happened to this area? Brain Pop Erosion