 Weathering is the
process that breaks down
rock and other
substances at the Earth’s
surface.
 Heat, cold, water, and ice
all contribute to
weathering.
 Repeated freezing and
thawing for example can
crack rock apart into
smaller pieces.
 Mechanical Weathering
(aka physical) breaking
rocks into smaller pieces.
 Mechanical Weathering
works slowly but over
long periods of time it
wears down whole
Mountains
 Mechanical Weathering in
Ireland
 Mechanical weathering breaks rocks in the
following manners:
 Frost Wedging: water collects into cracks, freezes, and
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expands breaking the rocks
Releasing pressure: remove top layer of rock, bottom rock
layers expands and breaks
Abrasion: wind and water pick up rock pieces and scrape
other rocks
Temperature Change: cold rocks heat up, expand, and break
Plucking: glaciers move and break off rock
Plants: roots grow and break rock apart
 Chemical weathering – process of
changing rocks into different ones
through chemical reactions
 Hydrolysis – rock reacts with water
and breaks down
 Ex: mineral feldspar turns into clay
 Oxidation – rock reacts with oxygen in
the air
 Ex: any rock with iron in it will turn red
 Carbonation – dissolved carbon
dioxide (CO2) in rain water makes it a
weak acid rain which dissolves marble
and limestone
 Acid rain – comes from pollution and
is much more destructive than
carbonation
 Organic (living) activity – plants or
animals produce chemicals which
break down rocks
 Ex: lichens – moss-like organism lives on
rocks
 The rate of weathering
usually depends on the
type of rock and the local
climate.
 Chemical weathering
occurs faster at higher
temperatures. Usually
were the climate is hot
and wet.
 The forces of weathering
breaks rocks into smaller
and smaller pieces. Then
the forces of erosion carry
the pieces away.
 Erosion is the movement of
rock particles by wind,
water, ice, or gravity.
 Weathering and Erosion
work together to wear
down and carry away the
rocks at the Earth’s surface.
 Weathering and erosion
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together can form things
like:
Caves
Canyons
Valleys
Arches
Steep Cliffside's
Remember this is
primarily caused by
wind, water, and gravity.
 Gravity’s role – gravity is the
force that pulls everything
down and is therefore the
force behind erosion
 Mass movement of rocks or
sediments can be fast or
slow.
 The different type of mass
movements caused by
gravity include landslides,
mudslides, slump, and
creep.
 Types of Erosion:
 Running water – streams,
rivers, currents, tides and
waves
 Glaciers – carries the largest
rocks, but moves the slowest
 Wind – moves small, dry
particles
 Plants, animals and humans
– burrowing, shoveling,
building, farming
 Mass movements – large
scale erosion includes creeps,
flows, slides, slumps,
avalanches and rock falls
 Grand Canyon Formation
 Deposition – when rocks and
sediments are laid down
(deposited)
 Deposition happens where the
wind, water or glacier stops moving
or drops the rock
 Examples of rock deposition:
 Sand dunes
 River deltas – when a river enters a
large body of water, slows down, and
drops the rock
 Beaches
 Soil
 So collectively erosion and weathering
break down rock and deposition
relocates the new sediments into
layered rocks or sedimentary rock.
 Soil – broken rock and
decayed organic (living)
matter
 Soil is the result of
chemical and mechanical
weathering over a long
period of time
 The type of soil depends on
the type of rock broken
down and the amount of
organic matter