Download Erosion and Sedimentation

Sediment
Notes #14
Terms (notes)
• Sediment is a naturally occurring material that has been broken
down.
• Weathering is the process of producing sediment from existing rocks,
minerals, and plant material.
• Erosion is the process of moving sediment from one location to
another.
• Deposition is the process of laying down (“depositing”) sediment.
Examples of sediment (not notes)
Peat
Clay
Sand
Betsiboka River,
Madagascar
Non-examples of sediment (not notes)
• As a table, discuss why the examples below are not sediment. Use
your definitions of sediment and weathering to explain why.
Rocky Outcropping
Icebergs
Used tires
Forces vs. Agents (notes)
• A force is what provides the energy for
action
• An agent is what actually does the
breaking down
• The main force for weathering and
erosion is gravity
Gravity (not notes)
• Gravity directly or indirectly powers the weathering and erosion on
this planet
Forces vs. Agents (not notes)
• As a table, identify the force and the agent in each of the following
examples:
A moving car
(What actually moves the
car? Where does it get its
energy?)
The final domino falling
(What actually pushes it
over? Where did it all
begin?
Agents of Weathering and Erosion (not notes)
• Each agent we discuss will have certain properties to the sediment
that it creates and moves.
• The main agents of erosion are wind, water, gravity, and ice
• For each agent we will discuss:
• The general appearance of the sediment produced.
• Whether the sediment is sorted or unsorted after being deposited.
Agent of Erosion – Wind (notes)
• Wind can only transport very small particles.
• Sediment is small and rounded.
• Sediment is sorted
Wind – Shaping the Land (not notes)
Even though it can only move small
particles, given time it can wear
away a large volume of rock.
Agent of Erosion – Water (notes)
• The most common and powerful agent of erosion.
• Sediment appears rounded and smooth
• Sediment is sorted
Water – River Structure (not notes)
• When rivers flow across an open area they
begin to meander (curve).
• This is because where the river flows faster on
the outer bank it wears away at the bank.
• Where the river flows slower on the inner
bank it drops off sediment.
• In extreme cases the river bends so far that
the tip breaks off and forms an “oxbow lake”.
Oxbow lakes beginning to form in Sandakan, Malaysia
An oxbow lake on the Danube River
Water – Waterfalls (not notes)
• Waterfalls occur when a hard layer of rock is on top of a softer layer.
Agent of Erosion – Gravity (notes)
• Gravity can act as a direct agent as well as the force that drives
erosion.
• Sediment appears jagged and angular
• Sediment is unsorted
(Rocks fall; aren’t you glad you came to school to learn this?) ->
Agents of Erosion – Ice (notes)
• Glaciers are massive sheets of ice that move slowly along the land.
• Glaciers are the only agent of erosion that can transport large
boulders.
• Sediment appears scratched
and grooved
• Sediment is completely unsorted
Glacial “till”
Boulder in Madison, New Hampshire, that was transported by a glacier
Valley Shape (notes)
• You can tell what formed a valley depending on its shape.
• A U-shaped valley is formed
by a glacier
• A V-shaped valley is formed
by running water