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

http://www.youtube.com/watch?v=lyysL02ZvQ8