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 impact River rocks are rounded and smoothed due to the repeated tumbling along the river bed as they roll downstream

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 Erosion moves the 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://teachertube.com/viewVideo.php?video_id=20814&title=Weathering_and_Erosion_b

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

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.

Mosaic of closely packed pebbles, boulders Alkaline, dark, and rich in humus Weak humus- mineral mixture Dry, brown to reddish-brown, with variable accumulations of clay, calcium carbonate, and soluble salts Clay, calcium compounds Desert Soil (hot, dry climate) Grassland Soil (semiarid climate)

Forest litter leaf mold Acid litter and humus Acidic light- colored humus Humus-mineral mixture Light-colored and acidic Light, grayish- brown, silt loam Iron and aluminum compounds mixed with clay Dark brown firm clay Humus and iron and aluminum compounds 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 (229) and compare rainfall amounts to topsoil depths. You will learn how rainfall affects topsoil depth.