1 Processes that Change Earth’s Surface S8.D.1.1.1,2,4 Unit 4 Lesson 1

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Processes that Change Earth’s Surface

S8.D.1.1.1,2,4

Unit 4

Lesson 1

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Weathering• Breakdown of rocks into smaller pieces called sediment

• 3 main causes of weathering

1. Liquid water

2. Ice

3. Wind

1. Physical Weathering

2. Chemical Weathering

examples

• 2 kinds of weathering

3Other examples

Physical Weathering• rock breaks into smaller pieces but its

chemical composition does not change• Also called Mechanical weathering

WIKI

Weathering

Unloading/ pressure release

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• The chemical composition of the rock changes• Rocks break down through chemical reactions• Air and water react with minerals in rock to create various chemical reactions

Chemical Weathering

Types of chemical

weathering

Types

Feldspar to Clay

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Erosion• Process by which sediment is moved over

Earth’s surface by water, wind, or ice

Houses undermined by coastal erosion in Pacifica, California. Photograph courtesy of NASA.

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Erosion• Most erosion happens over long periods

of time • rivers carving through land takes millions of years

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The Grand Canyon is an impressive example of stream erosion through rock

Erosion site

Erosion clip

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Erosion• Some erosion happens very quickly

• after heavy rains, fast moving water can carry large amounts of sediment away

• heavy rains can also cause landslides

• Soil erosion can be prevented by planting vegetation, trees, shrubs, and other plants.

• Roots of these plants will help hold soil in place. Soil will not be blown away by wind or washed away by water as easily

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Deposition/Sedimentation

• Process in which eroded sediment is dropped at another location Deposition animation

• Sediment may get transported thousands of miles by one of the world's major rivers, or it may just go from the top of the hill to the bottom during a landslide

*Increase erosion somewhere can cause an increase of sediment elsewhere

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Deposition/Sedimentation

• Most deposition happens when water or wind slow down

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Formation of Mountains

• When two of earth’s plates collide, mountains can form• The formation of mountains takes millions of years

Video clip of mountains forming

Appalachian Mountains

Pocono Mountains

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3 Types of Rocks

1. Sedimentary

2. Igneous

3. Metamorphic

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Sedimentary Rocks

• Form from:1. Sediment2. Remains of living things (coal)

• Sediment builds up and top layers put pressure on bottom layers squeezing the sediment together

• Over time, sediment in lower layers become cemented together to form sedimentary rock

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Sedimentary RocksSandstone Shale

LimestoneCoal

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Igneous Rocks

• Magma- molten rock underground

• Lava- molten rock above ground

• Igneous rock forms when molten rock cools and hardens– If it cools slowly, large crystals form– If it cools quickly, small crystals form (obsidian)

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Igneous Rocks

Granite

Pumice

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Metamorphic Rocks

• Form when heat and pressure change the chemical composition of a rock

• Rocks that are buried very deep are under extreme heat and pressures

• Minerals in the rock react to form new minerals

• Most metamorphic rocks in Pennsylvania formed from the continental collision responsible for the formation of the Appalachian Mountains

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Metamorphic RocksSlate

Marble Gneiss (nice)

Forms from shale

Forms from sandstone

Forms from limestone Form from granite

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Rock Cycle•Rocks can cycle between types if exposed to:

•heat and pressure•weathering and erosion•melting and cooling

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Rock Cycle

Rock cycle

AnimationRock Cycle Animation

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Fossils• Evidence that organisms existed in the distant past

• Can help scientists learn what ancient organisms– looked like

– where they lived

– when they became extinct

• Can also help scientists learn about Earth’s environments in the past.

•Ex. Finding a marine fossil somewhere would suggest that area was once underwater

• Estimated that one in a million organisms become a fossil

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