Surface Processes and Landscapes

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Surface Processes and Landscapes

• Weathering

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Weathering and Erosion

• Weathering is the chemical and physical breakdown
  of rocks into smaller fragments.
• Erosion is the movement of weathered material
  from one place to another.

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Weathering Types

• The two general types of weathering are physical
  and chemical.
• Physical weathering occurs when rock is cracked,
  split, or broken into sediments with no change in
  the rock composition.
• Chemical weathering occurs when rock is broken
  down by chemical action resulting in a change in
  the composition of the rock.

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Types of Physical Weathering

• Frost action caused by alternate freezing and
  thawing of water.
• Abrasion caused as rocks rub or bounce against
  each other.
• Exfoliation is the peeling away of large sheets
  of loosened surface material.
• Roots from large trees and shrubs as well as
  roots from lichens and mosses will split rocks as
  they grow.

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Types of Chemical Weathering

• Oxidation occurs when oxygen combines chemically
  with minerals. Ex. is rust.
• Hydration occurs when water combines chemically
  with minerals. Ex. is when feldspar or hornblende
  combine with water and form clay.
• Carbonation occurs when carbon dioxide combines
  with minerals. Example is carbonic acid which
  dissolves limestone creating caves, sink holes,
  stalactites and stalagmites.
• Organic Decay occurs when acids from decaying
  organic matter dissolve rock minerals.

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Soils

• Soil is one of the major products of weathering.
• Soil is the part of the weathered regolith in
  which rooted plants will grow.
• Soil is composed of rock minerals and organic
  matter and consists of all 3 states of matter.

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Soil Formation

• Soil types depend upon their place of origin.
• Soil formed by the weathering of the bedrock
  found beneath it is called residual soil.
• Soil formed from rock that was moved to its
  present location is called transported soil.

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Soil Profile

• As soils mature they grow richer and develop a
  series of layers called a profile.
• Topsoil is the uppermost layer containing the
  most organic matter and the most weathered rocks.
• Subsoil is below the topsoil and is rich in
  clay-sized particles but contains little organic
  matter.
• Below the subsoil is partly weathered bedrock on
  top of unweathered bedrock.

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Soil Solution

• A soil solution is the end product of weathering
  a solution of ground water containing ions of
  potassium, nitrate, phosphate, calcium and iron
  that the water picked up as it seeps through soil.

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Soil Conservation

• Due to the large demands upon earths farmable
  land, use of soil must be carefully planned and
  managed.
• Depletion occurs when too many nutrients are
  removed form the soil for crops to grow.
• Crop rotation, contour plowing, strip cropping,
  terracing, and wind breaks are all farming
  practices designed to preserve soil.

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Erosion

• Erosion is the transportation of loose sediments
  or rocks produced by weathering.
• The major mechanisms of erosion are
• Gravity
• Running water
• Glaciers
• Wind and
• Waves

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Types of Sediment

• Transported sediment is rock material that has
  been moved to another location.
• Transported materials will become abraded as they
  grind and bump against other rock material.
  These materials begin to appear rounded as they
  are abraded.
• Residual sediment is rock material that has
  weathered and remained in its place or origin.

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Running Water and Erosion

• Any running water makes a stream.
• Gradient, discharge, and channel shape influence
  a streams velocity and the erosion and
  deposition of sediments.
• Stream features include v-shaped valleys,
  deltas, flood plains and meanders.
• A watershed area is the area drained by a stream
  and its tributaries.

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Stream Velocity

• Carrying power is the ability of a stream to move
  particles of different sizes and this depends
  upon velocity.
• Velocity (speed) of a stream depends upon stream
  discharge and gradient.
• Discharge is the volume of water.
• Gradient is the steepness of the slope.

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Stream Velocity and Gradient
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Velocity and Channel Shape
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Velocity and Sediment Size

• Greater stream velocity will carry larger
  sediments.
• Stream load is the material that a stream carries.