2. Erosion & Weathering Changes

3. Essential Questions  What is weathering?  What is erosion?  What is the difference between slow and fast moving changes to the Earth’s surface?

4. What is Weathering?  WEATHERING is a process that breaks down rocks and wears down Earth’s surface.  Over time, weathering wears away mountains. Air, water, ice and organisms break rocks into smaller pieces.

5. What is Erosion?  Erosion is a destructive force in which pieces of rock are moved. EROSION occurs when wind, water, or ice move rock and soil. Ex. Waves are constantly eroding rocks, sand and soil along the coastline.Ex. Waves are constantly eroding rocks, sand and soil along the coastline. Ex. You already know that ice expands as it freezes. When water gets into the cracks and freezes, the rock expands and later is broken down into smaller parts.Ex. You already know that ice expands as it freezes. When water gets into the cracks and freezes, the rock expands and later is broken down into smaller parts.

6. More About… Weathering and Erosion Weathering is when rocks are broken down, like the Grand Canyon. Erosion can cause mudslides.

7. Weathering/Erosion Weathering… Weathering…  breaks down rocks  can form caves Erosion… Erosion…  can move sediments  can turn mountains into valleys and form lakes  can cause sand dunes

8.  The freezing and melting of water causes weathering. When water freezes, it expands. The ice in the cracks of the rock, push against the sides of the rock. Then the ice melts. Eventually, the rock will split apart. Icy Rocks

9.  You already have learned that weathering breaks down rocks and erosion moves the rocks. Now, lets look at fast and slow moving changes. Let’s See….

10. Slow Moving Changes  Earth’s surface is constantly changing. Weathering and Erosion are both considered Slow moving changes. One example of slow moving change is a sinkhole. It takes a long time for the ground to become unstable to sink in. Another example of a slow moving change is a canyon.

11. The Grand Canyon  The Grand Canyon is made primarily of sedimentary rocks. Rivers remove rock and soil. Over time, they carve out valleys. In some cases, rivers carve out deep canyons, such as the Grand Canyon.  You can see the jagged edges of the mountain which help us infer that rocks were broken down and later carried away.

15. Look at these Sedimentary Rocks- What do you notice?

16. Fast Moving Changes  One example of a fast moving change is a mudslide. Fast changes occur suddenly.  Volcanoes, earthquakes, hurricanes, and tsunamis are also fast moving changes.

17. Let’s Review  Which force wears away at Earth’s surface? A. volcanoesA. volcanoes B. weatheringB. weathering C. plates collidingC. plates colliding D. earthquakesD. earthquakes

18. Let’s Review  What process is responsible for the creation of sea stacks (as seen to the left)? A. weatheringA. weathering B. depositionB. deposition C. glaciersC. glaciers D. erosionD. erosion

19. Let’s Review  Which of the following does NOT cause erosion? A. evaporationA. evaporation B. windB. wind C. iceC. ice D. waterD. water

20. Let’s Review  Which process comes first, erosion or weathering? A: erosion B: weathering Weathering breaks down the rocks- Erosion moves the rocks

21. Let’s Review  Water can break down rocks because: A. water carries strong acids that erode rocksA. water carries strong acids that erode rocks B. water takes up less space when it freezes and rocks collapse inwardB. water takes up less space when it freezes and rocks collapse inward C. water expands when it freezes in cracks in rocksC. water expands when it freezes in cracks in rocks

22. Let’s Review  Many sandy beaches are particularly prone to erosion as a result of: A. TidesA. Tides B. RainB. Rain C. HumansC. Humans

23. Let’s Review Short Response  A strong hit from a hammer can help break apart rocks. What natural processes can help to weather or erode rocks?

24. Let’s Review Extended Response   Explain how ice can cause the erosion of a rock. Draw a diagram if it helps you explain your ideas.

25. Let’s Review Short Response  Bill invents a device which he says will entirely prevent soil erosion near rivers. Tests show that it does reduce erosion by 75%, but it doesn’t totally prevent it. Is Bill’s invention worth developing? Give 2 reasons why or why not.