Weathering, Erosion, and Deposition

Weathering

Weathering: rock materials are broken down into smaller pieces such as pebbles, sand, or soil materials

Types of Weathering

1. Mechanical: breaks down rock by physical means without changing its chemical composition• Caused by water, wind, ice, living organisms

2. Chemical: breaks down rock through chemical reactions• Oxygen, water, salts, and other substances can

react with the substances in rock and break, dissolve, or wash away the rock

Erosion

Erosion: the movement of weathered rock from one place to another

• Gradually occurs over long periods of time by…– ocean waves, rivers, streams, flooding, tsunamis,

glaciers, wind, gravity (landslides/mass wasting)

• Is considered a destructive process that breaks down Earth’s landforms

Look at the following pictures and name what type of erosion is

occurring

Baffin Island, Nunavut, Canada

• Waterfall (moving water)

Outer Banks, North Carolina

• Waves driven by ocean winds can cause the sandbars here to shift and change

Nevada's Great Basin National Park

• Wind

Rock Formation, Grand Canyon

• Winds sweeping through the Grand Canyon have eroded this sandstone outcrop into an anvil shape. Wind shapes these fantastical forms by eroding less dense rock, like sandstone, faster than surrounding rock.

Alaska's Saint Elias Mountains

• Bernard Glacier: Glaciers are slow but highly effective shapers of the land, essentially carrying away anything in their path—from soil and rocks to hills and even the sides of mountains.

Gulf of St-Lawrence, Québec

• Waves crashing against the shoreline

Deposition

Deposition: the dropping, or depositing, of pieces of rock that have been eroded by water, wind, ice, or gravity

• Is considered a constructive process that builds or creates Earth’s landforms

• The deposited pieces are called sediment

Delta Formation

• At the mouth of a river, where the river empties into an ocean or lake, the flowing water slows down and deposits the sediment it is carrying

• The sediment can build up to form a delta: a flat fan/triangle shaped piece of land at the river’s mouth

Mississippi River Delta

Nile River Delta

Erosion and Deposition

• Both are the result of interactions between Earth’s lithosphere and hydrosphere– Lithosphere: Earth’s rigid outer layer, which is

broken into tectonic plates– Hydrosphere: contains all of Earth’s water

(including liquid water, ice, and water vapor)

• Both are affected by factors like: slope of the land, sediment size, and speed of the water or wind

Video Clip

http://www.youtube.com/watch?v=ChEHQUMEkXw(shoreline erosion)