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