Weathering and Erosion

Weathering• The process that breaks down rocks and

other materials of Earth’s crust into smaller pieces.

Erosion

• The removal of rock particles by wind, water, ice, or gravity.

Weathering and erosion work together to wear down and carry away rocks on Earth’s surface

Avalon

Wildwood

Weathering

Weathering can happen two different ways

- Physical and Chemical

Physical Weathering

• Rock is physically broken down into smaller pieces

There are five types of physical weathering

1. Freezing and thawing

Frost Wedging

Frost Heaving

2. Plant Growth

3. Animal Actions

Burrowing of Animals

4. Friction and impactRiver rocks are rounded and smoothed due to the repeated tumbling along the river bed as they roll downstream

Evidence of past liquid water on Mars!

5. Temperature Changes

Rocks expand (get bigger) when they are hot, and contract (get smaller) when they are cold.

This brick wall has expanded and there is a visible crack

Chemical Weathering

• The process that breaks down rock through chemical changes.

There are five types of chemical weathering

1. Water

• Water weathers rock by dissolving it

2. Oxygen• Iron combines with

oxygen in the presence of water in a processes called oxidation

• The product of oxidation is rust

3. Carbon Dioxide

• CO2 dissolves in rain water and creates carbonic acid

• Carbonic acid easily weathers limestone and marble

4. Living Organisms

• Lichens that grow on rocks produce weak acids that chemically weather rock

5. Acid Rain• Chemicals from burning coal, oil and gas

react chemically with water forming acids.

• Acid rain causes very rapid chemical weathering

All this weathering can create interesting landforms

Formation of Devil’s Tower, Wyoming

http://www.youtube.com/watch?v=Hsh3_ZMKq-A

Karst Topography• A type of

landscape in rainy regions where there is limestone near the surface

• Created by chemical weathering of limestone

Features of Karst: Sinkholes

Features of Karst: Caves

Features of Karst: Disappearing Streams

Erosion

Erosion moves rock particles using four different methods

1. Water Erosion

• Rivers, streams, and runoff

http://www.youtube.com/watch?v=ReCt2AcydCg&feature=related

2. Ice Erosion

• Glaciers

http://www.youtube.com/watch?v=XOGbOOaPHsw&feature=related

3. Wind Erosion

http://www.youtube.com/watch?v=mecKnkc9qMk

4. Gravity

• Landslides, mudslides, slump and creep

http://www.youtube.com/watch?v=ZVjr4mii3cE&feature=player_embedded#!

Summary

• Weathering breaks down rocks– It can be physical (ice, plants, animals,

friction, temperature change) or chemical (water, oxidation, acid rain, carbon dioxide, living organisms)

• Erosion moves the rocks

• Together they produce soil

http://www.youtube.com/watch?v=HjVSiuj7Lxk

Soil

• Soil is made from rocks, minerals (mostly sand and clay), and organic materials

• Soil forms layers of different characteristics called horizons

What is soil?

• Soil is a material that forms the crust of the earth.

• It comes from the weathering of rocks and decomposition of organisms.

• It is formed very slowly.

What’s in soil?

• Minerals

• Organic matter

• Air and water

• Living organisms

Soil is found in layers called horizons

Soil-notice the layers in the soil

O horizon(green)

• O = Organic

• The top, organic layer made up mostly of leaf litter and humus.

• Humus is decomposed organic matter.

A horizon(dark brown)

• A = Topsoil.

• Dark colored

• Where seeds germinate and roots grow. This is generally the most productive layer of soil.

B horizon(light brown)

• B = Subsoil

• Lighter colored

• Contains clay and mineral deposits (iron, aluminum, etc)

C horizon(tan)

• C = Parent Material

• Layer of large unbroken rocks

R horizon(black)

• R = Bedrock.

• The solid rock that is under the soil

• Areas with a lot of humus and topsoil are great for growing plants.

Weak humus-mineral mixture

Mosaicof closelypackedpebbles,boulders

Dry, brown toreddish-brown, with variable accumulationsof clay, calciumcarbonate, andsoluble salts

Desert Soil(hot, dry climate)

Grassland Soil(semiarid climate)

Alkaline,dark,and richin humus

Clay,calciumcompounds

Acidiclight-coloredhumus

Iron andaluminumcompoundsmixed withclay

Forest litterleaf mold

Humus-mineralmixture

Light, grayish-brown, silt loam

Dark brownfirm clay

Acid litterand humus

Humus andiron andaluminumcompounds

Light-coloredand acidic

Tropical Rain Forest Soil(humid, tropical climate)

Deciduous Forest Soil(humid, mild climate)

Coniferous Forest Soil(humid, cold climate)

Soil lab online

• Tomorrow you will meet in the computer lab (123) and compare rainfall amounts to topsoil depths.

• You will learn how rainfall affects topsoil depth.

Remainder of the period

• Answer the review questions as a group.

• Use this diagram to label the layers pictured in #4. You will still need to name and describe them (except layer E)

• Sharpen and return pencils and cup