Download weathering & erosion

WEATHERING & EROSION
What is Weathering?
• Process by which
rocks on or near
Earth’s surface break
down and change.
MECHANICAL WEATHERING
• Also called physical
weathering.
• Changes rocks size and
shape but NOT
composition.
• EX:
– Frost Wedging: freezing
water expands in rock
causing cracks
– Pressure:
• from tree roots
• removal of rock layers
above. When rock layers
are removed, rock can
expand causing cracking.
CHEMICAL WEATHERING
• Changes rocks
composition
• New minerals are formed
• Determined by
– Composition of rock
• Calcite dissolves in acidic
water
– Temperature
• As temperature increases
so does rate of weathering
Water
• Hydrolysis- reaction
of water with other
substances.
Oxygen
• Oxidation- reaction of
oxygen with water.
• Iron reacts with
oxygen & creates rust
• Magnetite + oxgyen =
hematite
Acids
• Carbon dioxide,
nitrogen oxides, and
sulfur dioxides from
fossil fuels create
acids in atmosphere.
• Cause acid rain.
• These acids dissolve
minerals in rocks.
• Can also tarnish
metals
WHAT AFFECTS THE RATE
OF WEATHERING?
• Climate
– Temperature & precipitation
in an area
– Chemical weathering more
common where
temperatures & precip are
higher
– Physical weathering more
common where dry, and
cold (freezing & thawing
occur more common)
• Rock type &
composition
– Hardness
– Sedimentary rocks
more easily weathered
than hard igneous or
metamorphic
• Surface area
– Mechanical weathering
breaks rock up into
smaller pieces…
creating more surface
area for chemical
weathering to occur
• Topography & other
variables
– Sloped areas expose
fresh rock after
erosion. Fresh rock
can then be weathered.
– Decaying organic
matter releases CO2
which creates acid
which weathers rock
faster.
WHAT IS EROSION?
• Transporting
weathered materials
from one place to
another.
WATER
• Steeper slopes, faster
water flows
• Faster water flows,
more erosion occurs
• Rill erosion- creates
small channels
• Gully erosion- creates
deep, wide channels
COASTAL
EROSION
• Ocean waves & tides
also cause erosion
• Constant erosion of
beaches leads to
creation of sand bars
which eventually
become barrier
islands.
ICE
• Glaciers
– Scrape out large
sections of earth’s
landscape
– Carry large rocks &
debris over many miles
WIND
• Occur in areas with
limited rainfall and
high temperatures
• Most of these areas
have very little plantlife to hold soil in
place
• Creates dunes
PLANTS, ANIMALS,
HUMANS
• Minor impact
compared to water,
wind, glaciers
• When humans
excavate land, cause
erosion, leads to water
pollution
• When animals burrow,
shovel dirt somewhere
else.
DAILY QUIZ #1
1. The breakdown of rocks is
a. Erosion b. Weathering
c. Mass wasting
2. Oxidation is a form of
a. Mechanical weathering
b. Chemical weathering
3. When a rock changes in size & shape but not
composition, it went through
a. Mechanical weathering
b. Chemical weathering
4. Wind erosion can create
a. Glaciers
b. Mass wasting
5. Coastal erosion results from
a. Ocean Waves
b. Glacier formation
c. Chemical weathering
c. dunes