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Water Erosion and The Force
Transcript of Water Erosion and The Force
Moving water is the major agent of the erosion that has shaped Earth's land surface.
Runoff and Erosion Con't
Rills and Gullies:
Runoff and the materials run downhill due to gravity.
Runoff downhill forming tiny grooves in the soil are called
As the rills flow into one another, they grow larger, forming
that are large channels in soil that carries runoff.
These flow only after it rains.
Runoff and Erosion Con't
Streams and Rivers:
Gullies join together to form a larger channel called a
that allows water to continually flow.
Rarely dry up.
As streams flow together, they form larger and larger bodies of flowing water called a
Streams and rivers grow by receiving water from
, which are streams that flow into a larger stream.
Erosion by Rivers
Through erosion, a river creates valleys, waterfalls floodplains, meanders, and oxbow lakes.
Deposits by Rivers
Deposition creates landforms such as alluvial fans and deltas. It can also add soil to a river's flood plain.
Work and Energy
is the ability to do work or cause change.
Water Erosion and The Force
Runoff and Erosion
Erosion can be caused by a rain drop; can sink into the ground, evaporate, and even lift soil.
As water moves, it brings soil particles with it, called runoff.
is all the remaining water that moves over Earth's surface, and when it flows in a thin layer over the land it may cause sheet erosion.
Amount of Runoff depends on 5 Factors:
The amount of rain an area receives
Vegetation (plants absorb water)
Type of soil (some absorb more water than others)
Shape of the land (slopes=more gravity)
How people use the land
More runoff, more erosion
For example, the tributaries to the Ohio River form a system that drains large parts of eastern North America.
is the land area from which a river and its tributaries collect their water.
If you follow a river to it's source you'll reach it's
, the high ground between two drainage basins.
The flat, wide area of land along a river is a
, which is where the water flows during a river flood.
A river develops
, a loop-like bend in the course of a river, where it flows through easily eroded rock.
Meanders can cause an
, which is a cut off meander, where sediments dam off parts of the river.
Where a stream flows out of a steep, narrow mountain valley, the stream suddenly becomes wider and shallower.
It is a wide, sloping deposit of sediment formed where a stream leaves a mountain range.
A river ends it's journey when it hits a still body of water.
Sediment deposited where a river flows into an ocean or lake.
Soil on Flood Plains:
Heavy rains or snow melt cause a river to rise above its banks and spread out over its flood plain.
When the flood finally retreats, it deposits sediment as new soil.
Produces very fertile soil.
-energy that is stored and waiting to be used.
-energy an object has due to its motion.
As gravity pulls water down a slope, the water's potential energy changes to kinetic energy that can do work.
When energy does work, the energy is transferred from one object to another.
How Water Erodes and Carries Sediment
Most sediment washes or falls into the river as a result of mass movement and runoff. Other sediment erodes from the bottom or sides of the river.
is the wearing away of rock by a grinding action.
Grinds down sediment particles, creating smaller rocks and deeper stream beds.
The amount of sediment that a river carries is its
Large, heavy objects are usually dropped to the bottom and roll or slide while smaller particles are carried by faster moving water.
Erosion and Sediment Load
A river's slope, volume of flow, and the shape of its stream bed all affect how fast the river flows and how much sediment it can erode.
A fast river carries more and larger particles, and slow rivers deposit it's sediment load.
As a river's slope increases, its speed increases.
If a river's speed increases, its sediment load and power to erode may increase.
Volume of Flow:
The flow is the volume of water flowing past a given point in a river at a certain point.
A flooding river may have hundreds of times more eroding power than the river has at other times.
Stream bed Shape:
Affects the amount of friction between the water and the stream bed.
is the force that opposes the motion of one surface as it moves across another surface.
Where a river is deep, only a small fraction of the water comes in contact with the stream bed, reducing friction, allowing it to move faster.
Boulders and other obstacles can cause friction that moves every other way, called
Deposition occurs along the sides of the river, where the water moves more slowly.