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Geography > Rivers- Weathering And erosion > Flashcards

Rivers- Weathering And erosion Flashcards

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1
Q

Name 5 erosional processes:

A

1) hydraulic action
2) attrition
3) abrasion
4) solution
5) corasion (check spelling)

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2
Q

Name 4 transport processes:

A

1) traction
2) saltation
3) solution
4) suspension

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3
Q

Define the term ‘river’

A

Natural bodies of water that flow in open channels.

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4
Q

What is lithology?

A

The properties of rocks- mineral, composition, cracks, joints

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5
Q

What is the watershed?

A

The ‘line’ dividing two drainage basins.

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6
Q

What is flocculation?

A

The process in which clay and silt particles combine when fresh water mixes with the salt water. The heavier particles sink more rapidly.

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7
Q

What is the thalweg?

A

The line of maximum velocity in a river.

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8
Q

What is the helicoidal flow?

A

The corkscrew-like motion that occurs in a meander.

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9
Q

What is the bank full stage?

A

Where the channel variables (depth, width and velocity) of a river are unable to cope with additional water.

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10
Q

What are river cliffs?

A

Steep sided slopes on the outer bend of a meander.

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11
Q

What is a slip off slope?

A

The gently slope deposited on the under bend of a meander.

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12
Q

What is entrainment?

A

Picking up of particles from the ground/bed of a river.

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13
Q

What are unconsolidated rocks?

A

Loose, broken material that is often easily eroded.

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14
Q

What are consolidated rocks?

A

Solid rocks or sediments that have been bonded together by sedimentary cement.

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15
Q

What is the sediment yield?

A

The amount of material (debris) carried away by water.

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16
Q

What is the hydraulic radius?

A

The cross-sectional area of a river divided by the wetted perimeter.

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17
Q

What is the wetter perimeter?

A

The total length of the bed and base of a river channel in contact with the river.

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18
Q

What are pools?

A

The deep parts of a river located on the outer bend of a meander.

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19
Q

What are riffles?

A

The ridges- often formed of gravel- found in the straight part of a river between two meanders.

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20
Q

What is cavitation?

A

The explosion of air in joints and cracks as a result of air at very high pressure.

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21
Q

What is aspect?

A

The direction a slope faces; for example North- and South facing slopes.

22
Q

Name 5 types of mass movement:

A

1) rotational slip
2) Rock fall
3) slumping
4) mudflow
5) landslide

23
Q

Name three flow movements:

A

1) surface wash
2) sheetwash
3) through flow

24
Q

What is pressure release?

A

The process where overlying rocks, removed by erosion, cause underlying ones to expand and fracture parallel to the surface.

25
Q

What is the ‘line’ called that divides Britain into hard and soft rock?

A

The Tees-Exe Line

26
Q

Which to rivers does The Tees-Exe line run from?

A

River Tees and the River Exe

27
Q

What type of rock is South/East of The Tees-Exe line?

A

Soft rock such as chalk and clay.

28
Q

What type of rock is North/west of The Tees-Exe line?

A

Hard rock such as granite.

29
Q

How are braided channels formed?

A

When the main channel separated into a number of smaller interlocking channels. They occur when rivers don’t have the capacity to transport their load.

30
Q

State three factors which lead to the formation of braided channels:

A

1) a channel gradient which is steeper than meandering stream
2) load, large proportion of coarse material
3) highly variable discharge

31
Q

When do flood plains form?

A

When the channel variables cannot cope with river discharge.

River overflows into surrounding area so velocity decreases and the river had less energy so deposits it’s load.

Repeating flooding and deposition of alluvium.

32
Q

State three factors affecting slopes:

A

1) climate
2) aspect
3) rock type

33
Q

Name four mechanical weathering processes:

A

1) freeze-thaw
2) salt crystal growth
3) pressure release
4) disintegration

34
Q

Name four chemical weathering processes:

A

1) carbonation
2) hydrolysis
3) hydration
4) oxidation

35
Q

Name two types of biological weathering:

A

Animals and roots

36
Q

State two factors affecting weathering:

A

Climate and geology

37
Q

State three factors affecting river flow and velocity:

A

1) type of flow
2) channel shape
3) channel roughness

38
Q

State 5 factors affecting sediment yield:

A

1) relief
2) tectonic activity
3) storms
4) vegetation
5) human activity
6) type of sediment

39
Q

State two slow movements:

A

1) soil creep

2) rain-splash erosion

40
Q

Define levees:

A

Raised ridges running parallel to the edge of the channel and are formed by repeating flooding of a river.

41
Q

Describe the difference between material flood plains are made up of and levees:

A

Levees= coarse material like sand and gravel.

Flood plains= fine silt and clay.

42
Q

State two conditions needed to form deltas:

A

1) carry a large volume of sediment

2) enter a still body of water eg.. Sea or lake

43
Q

Why is deposition increased if water is salty?

A

Because salt particles group together and become heavier, river deposits it’s heaviest load first. This process is called flocculation.

44
Q

State two things which slow down the velocity of a river:

A

1) vegetation

2) flocculation

45
Q

Describe turbulent flow:

A

Water flow is not steady or uniform but turbulent, chaotic and eddying.

46
Q

State three conditions necessary for turbulent flow to occur:

A

1) complex channel shapes (eg.. Meanders, pools and riffles).
2) high velocities
3) cavitation (pockets of air explode under high pressure)

47
Q

Describe laminar flow:

A

The movement of water in a series of sheets. It is common in groundwater and glaciers, not so much in rivers unless they are very straight.

48
Q

State three conditions needed for laminar flow:

A

1) shallow channels
2) smooth, straight channels
3) low velocities

49
Q

How does channel roughness affect the velocity of a river?

A

Channel roughness causes direction that slows down the velocity of the water.

50
Q

How do you work out the hydraulic radius?

A

Hydraulic radius= cross-sectional area divided by wetted perimeter

Geography (17 decks)

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