Unit 1C - River Landscapes in the UK - River landforms of erosion and deposition

Question 1

Name landforms found in upper course?

Answer 1

Inter-locking spur, V-shaped valley, waterfall and gorge

Question 2

What is needed to create waterfall?

Answer 2

Hard rock followed by and over soft rock

Question 3

What is created when waterfall retreats?

Answer 3

A steep sided gorge

Question 4

How does a waterfall form?

Answer 4

• softer rock eroded, by h-a and abrasion, more than hard rock, creating a ‘step’ in river
• as water goes over step, it erodes more and more of softer rock
• steep drop eventually created (waterfall)

Question 5

How does a steep-sided gorge form from waterfall?

Answer 5

• hard rock eventually undercut by erosion and becomes unsupported and collapses
• collapsed rocks swirled around at foot of waterfall where they erode softer rock by abrasion, creating deep plunge pool
• over time, more undercutting causes more collapses. Waterfall will retreat, leaving a steep-sided gorge

Question 6

What are interlocking spurs?

Answer 6

• in upper course, most of erosion is vertically downwards, creating steep-sided, V-shaped valleys
• rivers aren’t powerful enough to erode laterally and have to wind around high hillsides that stick out into their paths on either side
• hillsides interlock with each other as river winds around them
  An area of hard rock around which the river winds

Question 7

Name landforms found in middle course?

Answer 7

Meander and ox-bow lake

Question 8

What is a meander?

Answer 8

A bend in a river

Question 9

What happens on outside bend of meander? Why?

Answer 9

River flows fast and erodes creating river cliff, as channel is deeper so less friction to slow current down

Question 10

What happens on inside bend of a meander? Why?

Answer 10

River flows slowly, depositing creating a slip off slope, as channel is shallower so more friction to slow current down

Question 11

What happens to create an ox-bow lake?

Answer 11

River erodes through neck of a meander on outside bend or flood occurs cutting off meander

Question 12

How does an ox-bow lake form from a meander?

Answer 12

• Meander gets larger over time and neck gets narrower due to continued lateral erosion through hydraulic action on outer bend
• river breaks through neck, either during a flood or erosion, and flows along shortest course
• deposition of rocks and soil at edges, cutting off meander and forming an ox-bow lake

Question 13

How does a meander scar form from an ox-bow lake?

Answer 13

Ox-bow lake eventually dries up leaving a meander scar

Question 14

Name landforms found in lower course?

Answer 14

Floodplain, levee and estuary

Question 15

What is a flood plain?

Answer 15

A large flat area either side of a river channel that floods

Question 16

2 things that build up flood plains?

Answer 16

• When river floods onto flood plain, water slows down and deposits eroded material that it’s transporting, building up flood plain.
• Meanders migrate across flood plain, making it wider, and downstream, flattening out valley floor. Deposition that happens on slip-off slopes of meanders builds up flood plain

Question 17

Levees and floodplains are depositional features and occur when a river flood, why?

Answer 17

More water in contact with surface when it floods so increased friction which slows speed of water as energy being used to overcome friction

Question 18

What are levees?

Answer 18

Natural embankments along edges of river channel

Question 19

How do levees form?

Answer 19

• During a flood, eroded material deposited over whole flood plain. Heaviest material deposited closest to channel as it gets dropped first when river slows down.
• Over time, deposited material builds up, creating levees along edges of channel

Question 20

Estuaries are created when?

Answer 20

When fresh and salt water meet at mouth and velocity falls as sea’s flow is slower than rivers’. As a result, sediment is deposited due to loss of energy

Question 21

How do estuaries form?

Answer 21

• Found at mouth, where river at its widest. Water here is tidal and floods over river banks, carrying silt ad sand onto valley floor.
• as tide reaches its highest point, water moving very slowly so sediment deposited
• over time, more and more mud builds up, creating large areas of mudflats
• at low tide, these are exposed

Question 22

On which river is landforms such as High Force Waterfall and Cross Fell at its source?

Answer 22

River Tees