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Weathering, Erosion, and Deposition Forces wear down and build up Earth’s surfaces Water erosion and a farm field Natural Forces move and deposit sediments The Grand Canyon was formed by the movement of water Water flowed over the land and carried away weather rock and soil This shaped a valley where water flowed creating the canyon Weathering ◆ Weathering is the process by which natural forces break down rocks. ◆ There are two types of weathering, mechanical and chemical. Weathering ◆ Mechanical Weathering is the breaking up of rocks by physical forces ◆ Ice wedging, pressure release, plant growth, or abrasion ◆ Chemical Weathering is the breakdown of rocks by chemical reactions that change the rocks’ composition. ◆ Dissolving or rusting Weathering Waves and Wind Shape the Land What natural force created these isolated stone pillars? The movement of water (waves). The constant action of waves breaking against the cliffs slowing wore the rock cliff away Erosion and Deposition ◆ Erosion- weathered particles are picked up and moved to a new place ◆ Deposition- the part of the erosion process in which sediment in placed (deposited) in a new location Gravity ◆ Gravity is the force holding everything down on Earth – This force causes water to move downward (think from the top of a mountain to the bottom) – In the process it carries and deposits sediment in new places Three types of Erosion ◆ ◆ ◆ Water erosion- rivers, streams carry sediment and deposit sediment at river bottom, floodplain, and mouth of the river Wind erosion- Strong winds life tiny particles of dust and carry them long distances Ice erosion- As ice moves slowly it carries with it rock and soil particles frozen inside of the ice Valleys and Floodplains As streams flow and carry sediment from the surface of the land they form valleys Floodplain- area of land on either side of the stream that is underwater when the stream floods Erosion Deposition Alluvial Fan- fanshaped deposit of sediment at the base of a mountain formed from a stream Delta- an area of land formed by the buildup of sediment at the end (mouth) of a river Deposition Sandbar- a ridge of sand built up by the action of waves → Barrier Islands- a sandbar that builds up over time creates a long narrow island parallel to the coast ←