Wearing Down Earth’s Surface Chapter 1 Lesson 2. Mechanical Weathering.
WEATHERING: Is the breakup of rock due to exposure to processes that occur at or near Earth’s...
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Transcript of WEATHERING: Is the breakup of rock due to exposure to processes that occur at or near Earth’s...
WEATHERING:
•Is the breakup of rock due to exposure to processes that occur at or near Earth’s surface
Types of Weathering
Mechanical Weathering
Chemical Weathering
Biomechanical Weathering
BiochemicalWeathering
Chemical Weathering
Biomechanical Weathering
BiochemicalWeathering
Ice Wedging
Abrasion:•The wearing away of rock material by grindingaction
Exfoliation: •The peeling of surface layers from exposed bedrock
Hydrolysis:•The chemical reaction of water with other substances
Abrasion
Exfoliation
Hydrolysis
Limestone Karst
Oxidation Oxidation of Desert Landscape
Weathering by Living Things (Biomechanical/Physical)
Weathering by Living Things (Biochemical)
EROSION:
•The removal and transport of materials by natural agents.
Transport Agents
WindWater
GlaciersGravity
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 betweenthe 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 istoo 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 leachedFrom 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.