Weathering and Erosion Notes
 Weathering is the breaking down of rocks and other materials on the
earth’s surface
Types of Weathering:
1. Physical or Mechanical Weathering– Breaks rocks into different shapes and
smaller pieces.
There is no change in the rocks chemical composition.
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Agents of Physical Weathering:
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Temperature : Changes in temp. cause repeated expansion and
contraction.
Ice Wedging: when liquid water goes into cracks and then freezes
causing the cracks to get wider.
Biological activity (root-pry, burrowing animals, human activities)
Unloading: The expanding of high pressure rock when exposed to a
lower pressure rock
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2. Chemical Weathering- The altering of the composition of minerals within a rock
that results in a reduction in size.
Agents of Chemical Weathering:
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Water: Dissolves minerals in rocks, making them weaker.
Acid: Dissolves minerals in rocks (examples: carbonic acid, acid rain,
and plant acid) Limestone and marble are the most affected types of
rocks.
Oxidation: Oxygen combines with iron minerals and sulfur minerals
changing the composition of the rock
Factors that determine the rate of Weathering:
 Composition: What the rock is made of
 Physical condition of rock:
-Cracks, holes, crevices – easier weathering
-Solid, unbroken – more weather resistant
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Erosion is the movement of weathered particles from one location to another,
where it is deposited.
The 4 main agents of erosion are:
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Water, Wind, Gravity, and Ice.
Water Erosion:
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Liquid water is the most common type of erosion.
Why?
Streams, raindrops, waves
Wind Erosion:
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Happens mainly in dry, windy climates.
Ex: Deserts, the beach (sand dunes)
Ice Erosion:
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Moving ice, in the form of glaciers, changes the surface of the Earth.
Glaciers are the most powerful form of erosion, but the least common.
Gravity Erosion:
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Movement of particles on steep slopes because of the influence of gravity.