Weathering Erosion Deposition The Wearing Down and Building

Weathering, Erosion , & Deposition The Wearing Down and Building Up of Earth

WEATHERING, EROSION, & DEPOSITION • Performance Indicator: 8. E. 5 A. 1 Develop and use models to explain how the process of weathering, erosion, and deposition change surface features in the environment.

WEATHERING • Weathering is any process that breaks down rocks and creates sediments. • There are two forms of weathering, chemical and mechanical (physical).

CHEMICAL WEATHERING • Chemical weathering is decomposition of rock caused by chemical reactions resulting in formation of new compounds.

EXAMPLES OF CHEMICAL WEATHERING • the process that breaks down rock through chemical changes. • The agents of chemical weathering: – water- water dissolves rock over time – oxygen- combines with iron to form rust (oxidation) – carbon dioxide- dissolves in water to form carbonic acid – living organisms- plant roots secrete acids – acid rain- from the burning of fossil fuels

Water • Water weathers rock by dissolving it.

Oxygen • Iron combines with oxygen in the presence of water in a processes called oxidation. • The product of oxidation is rust.

Carbon Dioxide • CO 2 dissolves in rain water and creates carbonic acid. • Carbonic acid easily weathers limestone and marble.

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

Acid Rain • Compounds from burning coal, oil and gas react chemically with water forming acids. • Acid rain causes very rapid chemical weathering.

2 factors that determine the rate of weathering: • rock type- Rock that is permeable (has holes that let water in), weathers faster than rock that is impermeable. The mineral content of rock also determines how fast a rock weathers. • climate- Rock weathers faster in warm, humid climates.

MECHANICAL WEATHERING • Mechanical (physical) weathering is the breakdown of rock into smaller pieces.

Mechanical Weathering • Process by which rocks are broken down into smaller pieces by physical forces. • Types of Mechanical weathering – Ice wedging – Plant roots – Abrasion – Burrowing of animals (animal action) – Temperature changes (freezing and thawing)

ICE (Frost) Wedging

PLANT ROOTS

ABRASION • mechanically weathered by abrasion. • Abrasion is weathering by grinding action.

These mountains in Salt Lake City, Utah, were also weathered by abrasion.

Abrasion

Animal Action (Burrowing)

How decomposers enrich soil and make it fertile: mechanical weathering. Chipmunks live in dens in the soil and search the litter for seeds and nuts. Plant roots break up the soil and hold it in place. Earthworms break up the soil, making it easier for plant roots to spread and for air and water to enter the soil. They create waste which makes soil more fertile by adding nitrogen. Bacteria are decomposers that break down animal and plant remains and wastes.

Freezing and Thawing (temperature changes)

Erosion • Erosion is the removal of rock particles from a location. • Caused by water, wind, ice, or gravity.

EROSION • Erosion is the process by which natural forces move weathered rock and soil from one place to another. Gravity, running water, glaciers, waves, and wind all cause erosion. The material moved by erosion is sediment.

GRAND CANYON, ARIZONA

WATER EROSION Water sources such as rivers, streams, ocean tides, and runoff can move rock particles away. .

Water Erosion-Rivers • Rivers and streams carry sediment. As the sediment moves mechanical weathering occurs. • Through water erosion, rivers create waterfalls, flood plains, and valleys.

Water Erosion-Waves • Waveswaves shape the coasts by transporting sand. While the sand is moved, mechanical weathering occurs. • Waves create sea stacks, caves, arch, and wave-cut cliffs.

Erosion by Runoff • As water from precipitation (rain, snow, etc. ) moves over the land, it carries particles with it. The moving water is called runoff. • Runoff creates rills and gullies.

WIND EROSION Sometimes the wind can move rock particles away: this can lead to dust storms!

WIND EROSION • Wind Erosion creates dust storms, hoodoos, and arches.

Ice Erosion As a glacier flows over the land, it picks up rocks in a process called plucking.

Ice Erosion Ice erosion creates: U -shaped valleys, glacial lakes, moraines, drumlins, and kettle lakes.

Think about it…. • Water is NEEDED by all living things to survive. – How does water change the planet?

Erosion by Gravity • Gravity causes sediment to move downhill. • It creates: landslides, mudflows, and creeps.

DEPOSITION • Deposition occurs when the agents (wind or water) of erosion lay down sediment. Deposition changes the shape of the land.

Deposition is the adding of sediment in an area as it settles out and forms new landforms. In this picture, taken in Squaw Creek, near Sisters, Oregon, rocks have been deposited along the bank of the river after heavy rains.

Deposition • In this picture, also taken in Squaw Creek, a sandbar has been formed by sediment that has been washed down the river. This might also be considered a spit.

Deposition • In this picture, salt has been deposited in the Great Salt Lake, Utah. You can see the salt deposits. They appear as white areas on the edge of the water.

Landforms • http: //www. classzone. com/books/earth_scie nce/terc/content/visualizations/es 1205/es 120 5 page 01. cfm? chapter_no=visualization

• Erosion, weathering, and deposition are at work everywhere on Earth. Gravity pulls everything toward the center of Earth causing rock and other materials to move downhill. Water’s movements (both on land underground) cause weathering and erosion, which change the land’s surface features and create underground formations.

The effects of these processes are as follows: • Changes in shape, size, and texture of landforms (i. e. mountains, riverbeds, and beaches). • Landslides • Buildings, statues, and roads wearing away. • Soil formation • Washes soil, pollutants, harmful sediments into waterways. • Causes metals to rust • Reduces beaches, shorelines. • Forms new landforms.

THE BREAK DOWN ACTIVITY SHEET • Weathering, Erosion , & Deposition: The Wearing Down and Building Up of Earth

Analyze your learning… Compare the relationship between weathering and erosion to the relationship between convergent and divergent boundaries.

Rate your learning…. • Where are you on the generic learning scale (0 -4) with: – Understanding erosion? – The difference between weathering and erosion? – Understanding how weathering and erosion work together?

Weathering and Erosion work together continuously to wear down and carry away the rocks at the Earth’s surface!!!!! END - Erosion

Deposition • Deposition is the process in which sediment laid down in new locations. • Caused by water, wind, ice, and gravity.

Think about it… • What needs to happen before deposition can occur? • Why did we study deposition last in our weather, erosion, & deposition mini unit?

Rate your learning…. • Where are you on the generic learning scale (0 -4) with: – Understanding deposition? – The connection between weathering, erosion, and deposition? – Understanding why deposition was studied AFTER weathering and erosion?