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geog - rivers
rivers
27
Geography
8th Grade
06/15/2006

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Cards

Term
what is a drainage basin?
Definition
this is an area of land drained by a river and its tributaries
Term
what is a watershed?
Definition
higher land which is the boundary of a river basin which separates two river basins
Term
what is the source?
Definition
the point at which a river begins
Term
what is a tributary?
Definition
a small stream of river flowing into a main river
Term
what is a confluence?
Definition
the place where a tributary joins the main river
Term
what is the mouth of a river?
Definition
the end of a river
Term
define transportation
Definition
movement of rocks, sediments and eroded materials down the river
Term
define erosion
Definition
the wearing away of land
Term
what are the 4 processes of erosion?
Definition
attrition, corrosion, corrasion, hydraulic action
Term
what are the 4 processes of deposition?
Definition
saltation, traction, suspension, solution
Term
what does traction mean?
Definition
large rocks and boulders are rolled along the bed of the river
Term
what does saltation mean?
Definition
smaller stones are bounced along the bed of a river in a leap-frogging motion
Term
what does solution mean?
Definition
dissolved material transported by the river
Term
what does suspension mean?
Definition
fine material, light enough in weight to be carried by the river. It is this material that discolors the water
Term
what does corrosion mean?
Definition
some rocks forming the banks and the bed of a river are dissolved by acids in the water
Term
what does corrasion (aka abrasion) mean?
Definition
fine material rubs against the river bank. The bank is worn away, by sand-papering action called abrasion, and collapses
Term
what does attrition mean?
Definition
material is moved along the bed of a river, collides with other material and breaks up smaller pieces
Term
what does hydraulic action mean?
Definition
the sheer force of water hitting the banks of the river
Term
what is the shape of the river and what type of spurs is there?
Definition
it is a v-shaped valley with interlocking spurs
Term
what happens after periods of heavy rain?
Definition
On the valley sides slowly moves downhill under gravity. The valley forms a V-shape as it deepened faster than it is widened.
Term
what happens in the upper course of the river?
Definition
steep, fast flowing river with little water. Lots of erosion
Term
what happens in the middle course of the river?
Definition
River starts to slow down. More water. Still eroding
Term
what happens in the lower course of the river?
Definition
River very slow. Much more water. Depositing here, NOT eroding
Term
what is an eddy?
Definition
Boulders broken off by erosion that sit on the river bed create swirling eddy currents as the water flows past as the river is not strong enough yet to move the boulders by traction.
Term
what do eddies do?
Definition
These eddies swirl the boulder round and erode a pothole in the river bed by abrasion.
Term
what is a braided channel?
Definition
In the summer months load is dropped by the low volume of low-energy water in the river. These build up to form obstructions in the river and it divides up the flow around them. In the winter, it is likely that the river volume will increase and remove these obstructions.
Term
what is a delta?
Definition
This deposition feature is one of the largest. When the flowing river hits the non-flowing sea, energy is suddenly lost. This causes all of the load in the river to drop in the river mouth. This builds up over time to create a delta – an area of land. The river divides into distributaries to continue to the sea which is now some way from its original meeting point. Lagoons and marshes can form.
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