Download Weathering and Erosion

WEATHERING:
•Is the breakup of rock due to exposure to
processes that occur at or near Earth’s
surface
Types of Weathering
Mechanical
Weathering
Biomechanical
Biomechanical
Weathering
Weathering
Chemical
Chemical
Weathering
Weathering
Biochemical
Biochemical
Weathering
Weathering
Ice Wedging
Abrasion:
•The wearing away of rock material by grinding
action
Exfoliation:
•The peeling of surface layers from exposed
bedrock
Hydrolysis:
•The chemical reaction of water with other
substances
Abrasion
Exfoliation
Hydrolysis
Limestone Karst
Oxidation of
Desert
Landscape
Oxidation
Weathering by Living Things
(Biomechanical/Physical)
Weathering by Living Things
(Biochemical)
EROSION:
•The removal and transport of materials
by natural agents.
Transport Agents
Wind
Water
Glaciers
Gravity
Volcanic Eruption
Wind
Water
Ice
Gravity
Volcanic Eruption
MASS WASTING
Types Mass Movement Erosion: (Mass
Movement )
• Talus – rock fragments that have been
weathered from a cliff and pulled down by
gravity.
Types Mass Movement Erosion:
(Mass Movement )
• Landslide – movement of a mass of bedrock
or loose soil and rock down a slope of a hill,
mountain, or cliff.
– usually occurs on steep slopes after heavy rains or
when large amounts of snow melt.
• (makes soil heavier and can
make a layer of water between
the soil and bedrock which
makes the soil easier for
gravity to pull down)
Types of Landslides:
(Mass Movement Erosion)
• Creep – slow, gradual movement of soil down
a slope.
– Objects fixed in the soil (fence) will also lean
downhill.
– The presence of water in soil contributes to creep.
Creep
Types of Landslides:
(Mass Movement Erosion)
• Slump - blocks of land tilt and move
downhill along a surface that curves into the
slope.
– Usually occurs because
the top of the slope is
too steep and the
bottom can’t support it.
Slump Animation
Slump
Types of Landslides:
(Mass Movement Erosion)
• Mudflow - rapid movement of
water that contains large amounts
of suspended clay and silts.
– Can travel up to 100km/Hr
– can move rock, boulders, trees, and houses
– occurs in drier regions that get infrequent, but
heavy rainfall
Mudflow
Types of Landslides:
(Mass Movement Erosion)
• Earthflow - mass of weathered material
saturated with water flows downhill
– Slower and less fluid than a mudflow.
– speed depends on the amount of water in soil,
composition of soil, and steepness of slope
– can last a couple of days to years
Earthflow
Types of Landslides:
(Mass Movement Erosion)
• Lahar - mudflow that accompanies a volcanic
eruption.
– heat from the erupted material melts the snow on
top of a volcano which and it moves down the side
of the volcano.
Lahar
Soils
Soil is a combination of highly
weathered clastic sediments
(mostly sand, silt and clay),
chemical sediments and organic
material in which plants can
grow.
The material from which soil is
formed is called Parent Material.
A soil can either be a Transported
Soil or a Residual Soil.
Soils formed from sediments that were
produced elsewhere are called
Transported Soils
(Example: Glacial and Alluvial Soils)
A soil whose parent material is the
bedrock beneath it is a
Residual Soil
Residual Soils form as their parent material is
weathered away. How fast this happens depends
on four things:
1. The rock type of the parent material (ex.
some rocks are more chemically stable than
others)
2. Climate (high rainfall, hot temps. Increase
rate of soil formation)
3. Plant and Animal Activity (Biochemical and
Biomechanical Weathering)
4. Slope (A deep soil can’t form on a slope)
A cross-section of a soil, from the
surface (A) to the un-weathered
parent material (R) is called a Soil
Profile.
(A)
(B)
(C)
(R)
Organic remains (Humus)
Fine particles of weathered parent material mixed with Humus- Topsoil
Clays, Iron Oxides and dissolved minerals that have leached
From above- Subsoil, usually brown or red
Partially weathered parent material- Rock Fragments
Parent Rock- “Bedrock”
Soil Formation Sequence
Conditions in which soils develop in different
locations cause the profiles of soils to vary in
appearance. What causes this variation is the
composition, appearance and thickness of the 4
major layers or Horizons of a soil profile.
Examples of Soil Profiles from
around the World (Different types
of soils)
Soil Fertility-The ability of a soil to grow plants.
Since different types of plants have different nutrient
requirements, different soil types have different plant
populations.
Harvesting crops that have used nutrients
from the soil, removes those nutrients from
the ground. This can cause soil to become
depleted of nutrients. Several things can
prevent this:
1. Allowing fields to remain “fallow” for a
period.
2. Crop rotation.
3. Fertilizing (downsides-nutrients in
runoff).
Salinization- The build-up of
dissolved minerals that are
concentrated in lower soil
horizons, and are brought to the
surface through irrigation.