Erosion And Deposition Flashcards
What is erosion
Erosion is the wearing away of the earths surface by the movement of weathered material.
What are the three main agents of erosion
Water
Wind
Ice
What is the difference between erosion and weathering.
Erosion wears away the earths surface through moving objects scouring the surface whilst weathering happens in one place.
What is weathering
It is the breaking down of rocks and soil by actions of the weather.
What is deposition
Deposition is the build-up of the weathered material that has been removed from the earths surface.
What does weathering and erosion produce
Loose stones, soil, and mud
What are deposition features
Features that form part of a landscape, created by deposition.
Eg: beaches, sand dunes.
What are agents of erosion
Forces of nature that cause erosion.
What is abrasion
It is the wearing away of the of the river banks or bed by the rivers load
What is the start of a river called
The source
What is the place where a river flows into the sea called
The mouth
What is a river course
It is the length from the rivers source to mouth.
What is river erosion and deposition influenced by
The speed the river flows at
The amount of water in the river
What are the 3 sections of a river
Upper course
Middle course
Lower course
What are the features of the upper course
The gradient is the steepest The width is narrow Vertical erosion takes place Flows the fastest Shallow depth Creates waterfalls and Rapids
What is vertical erosion
It is when the bed of the river is eroded and deepens the river channel
What causes the river to move so fast
The steep gradient
What weathers materials do rivers transport
Sand
Rock
Mud
Stones
What is the spare energy in the upper course used for
To transport the large rocks
How can erosion take place in the upper course
The movement of these large rocks against the bed of the river causes Vertical erosion
Why are the sides of the valley so steep
So loose stones and soil can easily be washed into the river and add to the load
What is a waterfall
It is a sudden drop in the gradient of a river,that looks like a cliff or sharp slope.
Why do waterfalls occur
When the course of a river flows or soft rock that rock erodes quicker and creates a step in the bed.
What are plunge pools and how are they formed
It is a small eroded pool of a river bed at the base of a waterfall due to the harder rocks of the land breaking off and falling into the river and being stirred around by the force of the waterfall.
What are Rapids
They are fast flowing area of a river
How are Rapids formed
When different types of rock cross the river course. The hard and soft rock erode differently causing uneven layers in the river bed.
What are potholes
Potholes are deep surfaces in the ground.
How do potholes occur
When stones carried in the load of a river spin around by the river currents. This action wears away deep holes in the river bed.
What are Rapids
They are fast flowing area of a river
How are Rapids formed
When different types of rock cross the river course. The hard and soft rock erode differently causing uneven layers in the river bed.
What is a delta
A fan-shaped (semi-circular) area of sand and silt deposited at the mouth of a river.
How do deltas form
When a river reaches a large area of water such as the sea, the river banks are low so that water can flow over them. The water spreads out and deposits load. This causes the river to divide into smaller channels.
Why doesn’t South Africa have large deltas
Because the force of our ocean waves and currents are too strong for deltas to form.
What is a floodplain
It is a wide, flat area next to the river channel, usually covered by flood water.
How are floodplains formed
When lighter silt and mud deposit on the flat valley floor
What is a levee
A levee is deposition on top of a river bank,formed when river floods.
How are levees formed
When a river floods the heavier load of the river material is deposited on the river bank.
What is silt
It is either fine sand or rich soil from weathered material.
What is a meander
The winding path that a river takes around obstacles for it has less energy to go over them.
How do meanders form
By erosion around an obstacle (large rocks)
What is an ox-bow lake
It is the remainder of a meander after being cut of by river erosion.
How do of-bow lakes form
By repeated erosion on the outside of a meander, narrowing the distance between the two meanders. Deposition from the river load cuts off the old meander and makes it a short cut for the new path.
What are the features of the middle and lower course of a river
Flatter land Erosion is lateral Slip offs River cliffs Meanders Ox-bow lakes Current is weaker
What is lateral erosion
It is erosion that takes place sideways
What is a river cliff
The outside bank of a river that undergoes erosion
How are river cliffs formed
Because the current on the outside bend is faster, it erodes the bank and forms a river cliff.
What is a slip of
It is the inside bank of a river that undergoes deposition
How does a slip off form
Because the current on the inside of the river bend is weaker or slower, some of the load is deposited on the slip off slope.
What causes meanders to change their shape and position
Erosion
Deposition
