WEATHERING AND EROSION
UNIT 4 STUDY GUIDE
Unit Test on ______________.
- Changing Earth’s Surface
THE BIG IDEA OF THIS UNIT:
Weathering, erosion, and deposition act together in a
cycle that wears down and builds up the Earth’s surface.
Weathering

the process by which rock is broken down very
slowly (much slower than earthquake activity,
landslides, or volcanic activity)
Just breaking downnot moving yet!
Mechanical Weathering

breakdown of rock into smaller pieces by
physical means
The rock is still a rock, just smaller.
Ice Wedging

alternate freezing and thawing of water that seeps
into the cracks of rocks and cause breakage
Ex. potholes
Ice Wedging
Yosemite National Park, California
Abrasion

the grinding and wearing away of rock by wind,
water, or gravity
Exfoliation

the peeling or flaking of rock due to repeating
heating and cooling
Exfoliation
Plants

the roots of plants grow down into the rock
and eventually bust it apart (root pry is an
example)
Root Pry
Animals

can wear down rock as well
Animals
Animal burrowing
causes weathering to
occur.

Chemical Weathering

rock breaks down as a result of a chemical reaction
It doesn’t just look different, it IS different!
Acid Precipitation

rain, sleet, or snow that contains a high
concentration of acids (sulfur, nitrogen, and carbon
oxides); acid rain can dissolve the limestone that is
on some buildings.
Acid Precipitation
Plant acids (Humic acids)

moss and lichens, which are fungi and algae living
together, can break down rock
Oxidation

oxygen in the air can cause rust
Weathering creates sediments.
Then, sediments get carried away.
Erosion- the process in which weathered
rock and soil (sediments) are transported/
moved from one place to another; Example
– The Rocky Mountains have sharp peaks
and are younger than the Appalachian
Mountains because they haven’t been
eroded as much.
Erosion
4 Agents (causes) of Erosion:
1)
2)
3)
4)
Gravity
Water
Wind
Waves
1) Gravity/Mass Movement
when gravity pulls rocks and soil downhill
a.
Landslide – sudden mass erosion of rocks, trees, and
soil downhill
Landslide Video
• http://www.youtube.com/watch?v=CUXhjP
kGBtU
Gravity/Mass movement
b. Mudslide- sudden mass erosion of mud downhill
Click on the video link.
http://www.youtube.com/watch?v=n1cCs-S5EKc
Gravity/Mass Movement
c. Creep – slow movement of
soil, rocks, and plants
down a slope where
plant roots and tree
trunks begin to lean
toward the soil as
erosion continues
Creep
- The Force of Moving Water
2) Water

happens when water picks up materials and carries
them away; running water changes the Earth’s
surface more than any other agent
a.
Runoff – water flowing across the Earth’s surface;
most sediment washes or falls into a river
b. Rivers – V-shaped valleys and canyons can be caused
by erosion from running water
c. Glaciers – frozen “rivers of ice” that can make Ushaped valleys
- Glaciers
How Glacier Erosion Shapes the Land
V-shaped by water, followed by U-shaped by ice
U-shaped Valley
3) Wind

occurs when wind picks up loose sediments and
carries them in the air
- Wind
Wind Erosion
SANDSTORM LEAVING NORTH AFRICA TOWARDS
THE ATLANTIC – CANARY ISLAND.
Wind Erosion- The Dust Bowl

Wind erosion is one cause of
soil loss. For example, wind
erosion contributed to the Dust
Bowl on the Great Plains. The
Dust Bowl ruined farmland in
western Oklahoma and parts
of the surrounding states.
Wind blew dry particles of
soil into great clouds of dust
that traveled thousands of
kilometers.
Slide 6