Essential Question How does weathering and erosion impact earth’s surface features?

Weathering The natural breaking down of rocks and other materials on the Earth’s surface. A slow continuous process that affects all substances exposed to the atmosphere. Two types of weathering: Mechanical Chemical

Mechanical Weathering Forces of nature break rock into smaller pieces without changing the chemical make up of the rock. Rocks are broken into smaller pieces Fragments tend to become rounder as weathering continues. 5 types of Mechanical Weathering

Temperature Repeated heating and cooling of outer surface of rock causes outer layers to break off. Breaking of outer layers called: Exfoliation.

Ice Wedging Water seeps into cracks in rocks. Temperature drops and water in cracks freezes and expands widening the crack.

Organic Activity Mechanical Weathering caused by plants or animals. Could be animals simply walking. Root-pry: roots in cracks of rocks widen cracks as the root grows.

Gravity Pulls loose material down. As rocks fall they collide and break.

Abrasion Wearing away by solid particles carried by wind or water.

Chemical Weathering Weathering which changes the mineral composition of rocks through chemical reactions. Most often involves water.

3 Types of Chemical Weathering 1. Water Water dissolves minerals and carries them away. Water can form weak acid with many chemicals. 2. Acid formation Mild acids form and breakdown minerals Plants (Lichens) can often form mild acids that breakdown rock material 3. Oxidation Oxygen in the air combines with minerals to form new compounds Rusting is an example

Erosion and Deposition

Breaking Down Processes Erosion The process by which weathered rock and soil particles are moved from place to place. Deposition The process by which weathered sediments are laid down in a new location creating new landforms.

5 Agents of Erosion Gravity Glaciers Wind Surface Water / Running Water Ocean Shoreline / Ocean Waves

Gravity Pulls rock and soil down a slope Called Mass Movement Rapid Rockslides Mudflow Avalanche Slow Slump Creep

Glaciers Carry very large to very small debris Most powerful agent Deposits Form piles called moraines Drumlins – little mounds Glacial lakes Kettle lakes U-shaped valleys

Wind Removes loose material from the earth’s surface. Amount of material carried depends on wind speed Most active in deserts, plowed fields, beaches Deposits by wind Loess- layer of fine silt or sand Dunes- mounds of sand

Running Water MAJOR CAUSE OF EROSION When water moves it carries particle called the load. Speed of water determines the size of the load Creates canyons and valleys River deposits Delta Oxbow lake Flood plains

Waves Constantly erode and shape the shoreline. Formation Sea cliffs Sea stacks and caves Deposits Beaches Spits sand bars Barrier Islands

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