Erosion & WeatheringErosion & WeatheringChangesChanges

Essential QuestionsEssential Questions

What is weathering?What is weathering? What is erosion?What is erosion? What is the difference between slow What is the difference between slow

and fast moving changes to the and fast moving changes to the Earth’s surface?Earth’s surface?

What is Weathering?What is Weathering?

WEATHERINGWEATHERING is a is a process that breaks down process that breaks down rocks and wears down rocks and wears down Earth’s surface.Earth’s surface.

Over time, weathering Over time, weathering wears away mountains. wears away mountains. Air, water, ice and Air, water, ice and organisms break rocks organisms break rocks into smaller pieces. into smaller pieces.

What is Erosion?What is Erosion? Erosion is a destructive force in Erosion is a destructive force in

which pieces of rock are moved. which pieces of rock are moved. EROSIONEROSION occurs when wind, water, occurs when wind, water, or ice or ice movemove rock and soil. rock and soil. • Ex. Waves are constantly eroding rocks, Ex. Waves are constantly eroding rocks,

sand and soil along the coastline. sand and soil along the coastline. • Ex. You already know that ice expands Ex. You already know that ice expands

as it freezes. When water gets into the as it freezes. When water gets into the cracks and freezes, the rock expands cracks and freezes, the rock expands and later is broken down into smaller and later is broken down into smaller parts.parts.

More About… More About… Weathering and ErosionWeathering and Erosion

Weathering is when Weathering is when

rocks are broken rocks are broken

down, like the Grand down, like the Grand

Canyon.Canyon.

Erosion can cause Erosion can cause

mudslides.mudslides.

Weathering/ErosionWeathering/Erosion

Weathering…Weathering… breaks down rocksbreaks down rocks can form cavescan form caves

Erosion…Erosion… can move sedimentscan move sediments can turn mountains can turn mountains

into valleys and form into valleys and form lakeslakes

can cause sand can cause sand dunesdunes

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

Icy RocksIcy Rocks

You already have learned that You already have learned that weathering breaks down rocks and weathering breaks down rocks and erosion moves the rocks. Now, lets erosion moves the rocks. Now, lets look at fast and slow moving look at fast and slow moving changes.changes.

Let’s See….Let’s See….

Slow Moving ChangesSlow Moving Changes Earth’s surface is Earth’s surface is

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

The Grand CanyonThe Grand Canyon

The Grand Canyon is made primarily The Grand Canyon is made primarily of sedimentary rocks. Rivers remove of sedimentary rocks. Rivers remove rock and soil. Over time, they carve rock and soil. Over time, they carve out valleys. In some cases, rivers out valleys. In some cases, rivers carve out deep canyons, such as the carve out deep canyons, such as the Grand Canyon. Grand Canyon.

You can see the jagged edges of the You can see the jagged edges of the mountain which help us infer that mountain which help us infer that rocks were broken down and later rocks were broken down and later carried away. carried away.

Look at these Sedimentary Rocks- What do you notice?

Fast Moving ChangesFast Moving Changes

One example of a fast moving One example of a fast moving change is a mudslide. Fast changes change is a mudslide. Fast changes occur suddenly.occur suddenly.

Volcanoes, earthquakes, hurricanes, Volcanoes, earthquakes, hurricanes, and tsunamis are also fast moving and tsunamis are also fast moving changes.changes.

Let’s ReviewLet’s Review

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

Let’s ReviewLet’s Review

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

Let’s ReviewLet’s Review

Which of the following does Which of the following does NOTNOT cause erosion?cause erosion?• A. evaporationA. evaporation• B. windB. wind• C. iceC. ice• D. waterD. water

Let’s ReviewLet’s Review

Which process comes first, Which process comes first, erosion or weathering?erosion or weathering?

A: A: erosionerosionB: B: weatheringweathering

Weathering breaks down the rocks- Erosion moves the rocks

Let’s ReviewLet’s Review

Water can break down rocks Water can break down rocks because:because:• A. water carries strong acids that erode A. water carries strong acids that erode

rocksrocks• B. water takes up less space when it B. water takes up less space when it

freezes and rocks collapse inwardfreezes and rocks collapse inward• C. water expands when it freezes in C. water expands when it freezes in

cracks in rocks cracks in rocks

Let’s ReviewLet’s Review

Many sandy beaches are particularly Many sandy beaches are particularly prone to erosion as a result of:prone to erosion as a result of:• A. TidesA. Tides• B. RainB. Rain• C. HumansC. Humans

Let’s ReviewLet’s ReviewShort ResponseShort Response

A strong hit from a hammer can help A strong hit from a hammer can help break apart rocks. What natural break apart rocks. What natural processes can help to weather or processes can help to weather or erode rocks?erode rocks?

Let’s ReviewLet’s ReviewExtended ResponseExtended Response

Explain how ice can cause the erosion of a rock. Draw a diagram if it helps you explain your ideas.

Let’s ReviewLet’s ReviewShort ResponseShort Response

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