Download Weathering PPT

Weathering
Weathering

Process that breaks down and changes
rock at or near earth’s surface


Mechanical – rock is broken into smaller
pieces by physical means
Chemical – rock undergoes changes due to a
chemical change in composition
Mechanical Weathering

Two factors that are important to mechanical
weathering are temperature and pressure.
Frost wedging
Exfoliation

bedrock is under pressure within the earth; as it is
exposed to the surface the pressure is reduced and the
rock expands and long curved cracks form; layers of rock
are stripped away

Root action
Abrasion
Chemical Weathering

Chemical reactions take place that alter
the rocks composition




Water: can dissolve many kinds of
minerals and rock
Oxygen: can combine in chemical
reactions with other substances –
oxidation. Example: rust
Carbon dioxide combines with water in the
atmosphere to create carbonic acid which
dissolves rocks
Acid precipitation
Factors affecting the rate of
weathering




Climate
Rock type and composition
Surface area
topography
Erosion

The transport of weathered material form
one place to another
Forces that aid erosion


The force of gravity tends to pull materials
downslope.
http://www.youtube.com/watch?v=XC9AqJlaCj4&feature=related
Running water
Running water has greater erosional power than
wind and can move more material greater
distances.
 As the slope of the
land decreases, the water
slows and larger
particles are deposited.

http://www.youtube.com/watch?v=MFpCJsc_k64
Glacial erosion

Due to their high density glaciers carry huge
rocks and piles of debris and scratch and grind
over surfaces.
Erosion by abrasion

http://www.youtube.com/watch?v=D5uDaEpJHjE

Wind erosion


Wind picks up and moves fine particles
Prevalent in areas of low precipitation and high
temperatures
Wind erosion

http://www.youtube.com/watch?v=PQmo
n7Rj6ns&feature=related
Mass Movements


The downslope movement of loose
sediment and weathered rock due to
gravity
Influenced by




weight of material
materials resistance to sliding/flowing
a trigger
water
Types of mass movement



Creep – slow, steady downhill movement
Flows – materials flow as if thick liquid
Slides – rapid, downslope movement of a thin layer of
material that separates from underlying bedrock

Slumps –

Avalanches –

Rock falls –
mass of material rotates and slides along a
curved surface
landslides that occur in mountainous
areas with thick accumulations of snow
rocks break loose and fall downward





Good Catch
That's a Big Rock
Washington Mudslide
Glad I Wasn't Standing There
Even More Thankful I Wasn't Driving