Rivers Flashcards
(52 cards)
The boundary of a drainage basin separating one drainage basin from another?
Water shed
A point where two streams or rivers meet
Confluence
The starting point of a stream or river, typically, upper course
Source
Area of land drained by a river
Drainage basin
The end of a river
Mouth
How fast the river is flowing
Velocity
The volume and speed at which water flows through the river channel
Discharge
The breakdown and decay of rock by natural processes, usually acting on the river valley sides
Weathering
The movement of rocks and soil downslope due to gravity, helped by weaker rocks, steep slopes and heavy rainfall. Mass movements can be very slow - only a few millimetres a year- or sudden and rapid.
Mass movement
Involves the action of water wearing away the rocks and soils on the valley bottom and sides
Erosion
Where a river picks up and carries material as it flows downstream
Transportation
When a river no longer has enough energy to carry its load, this occurs. As the river’s discharge and velocity reduce, the heaviest material is deposited first- for example, after flooding events
Deposition
This happens when rainwater enters cracks or gaps in the rock then freeze if temperatures drop below zero. The water expands as it turns into ice and then exerts pressure on the rock, causing it to break into smaller pieces.
Freeze-thaw
The roots of plants, especially trees, can grow into cracks in a rock and split the rock apart
Biological weathering
Rainwater contains weak acids that react with some types of rocks, for example, the carbonates in limestone are dissolved by these acids and the rock breaks up
Carbonation
Results from the sheer force of the water hitting the river bed and banks and wearing them away. This action is particularly important during high-velocity flows
Hydraulic action
When pebbles grind along the riverbank and bed in a sand-papering effect.
Abrasion
When rocks that the river is carrying knock against each other. They break apart to become smaller and more rounded.
Attrition
When the water dissolves certain types of rocks, eg limestone.
Corrosion
Where the individual particles of soil move slowly down a slope from the force of gravity
rock-fall
Where material moves rapidly downslope in one go, for example, in a landslide. In a slump, the material often rotates as it moves.
Slumping
Where masses of soil or rock, usually mixed with water, flow like liquid downhill.
Mud-flow.
Name the 4 processes of erosion
Abrasion / corrasion
Corrosion
Hydraulic action
Attrition
What is abrasion / corrasion
Sandpaper action
