River Landforms

Question 1

what is an interlocking spur

Answer 1

• an interlocking spur is an acute, gently sloped valley with a deepened channel

Question 2

how do interlocking spurs form

Answer 2

• potential and kinetic energy causes river to vertically cut into channel
• which creates a deep channel by hydraulic action and freeze thaw
• resistance along the way causes river to change direction and meander, making spurs of highland to interlock

Question 3

what are rapids

Answer 3

areas of shallow, fast-flowing water in a stream

Question 4

how are rapids formed

Answer 4

• they form downstream of a waterfall where water flow is straighter and quicker
• they mark the point of a previous waterfall

Question 5

what is a waterfall

Answer 5

a waterfall is a cascade of water falling from a height

Question 6

when are waterfalls formed

Answer 6

when a river flows over an area of hard rock followed by an area of softer rock

Question 7

what is a gorge

Answer 7

• a gorge is a high valley side located directly downstream a waterfall
• it is a steep sided valley with rocky walls

Question 8

how are gorges formed

Answer 8

• they are formed as waterfall retreats upstream
• it leaves a steep sided valley called a gorge
• every time over changing cap rock breaks off the gorge retreats and grows longer

Question 9

what is an oxbow lake

Answer 9

an oxbow lake is a horseshoe shaped lake that was previously part of a river

Question 10

how is an oxbow lake formed

Answer 10

• narrow neck of meander is laterally eroded
• narrower neck gets flooded by river to create shortcut to main channel
• process of flooding repeats and erodes narrow neck
• redundant loop cut from main channel
• high velocity river deposits material on the the outside
• creates a body of land between river and loop
• marsh plants colonise deposited material

Question 11

what is the result of the process of an oxbow lake being formed

Answer 11

a straightened river channel and an isolated loop lake (oxbow lake)

Question 12

the four simplified stages of oxbow lake creation

Answer 12

• erosion
• flooding
• new course
• oxbow lake

Question 13

what is a flood plain

Answer 13

• a flood plain is made by a period of prolonged heavy rain
• causing an increase in rivers discharge
• so water rises over banks and floods surrounding land
• repetition builds up levees and flood plain

Question 14

stage 1 of a flood plain

Answer 14

• before levee

- silt deposits on flood plain

Question 15

stage 2 of a flood plain

Answer 15

• during a flood

- heavy deposited material nearer the river bed and fine sediment further on flood plain

Question 16

stage 3 of a flood plain

Answer 16

• raised bank either side of river a natural levees

- river bed builds up bed load that deposits overtime

Question 17

4 characteristics of flood plains

Answer 17

• large area of flat land
• layers of alluvium cover flood plain
• oxbow lakes
• reeds and marsh plants

Question 18

where are levees found in a river

Answer 18

in the lower course

Question 19

how is a waterfall formed

Answer 19

• softer rock is eroded by hydraulic action and abrasion more than hard rock
• creating a step
• as water goes over step it erodes more soft rock
• a steep drop is eventually created, forming the water fall

Question 20

how is a gorge formed (after a waterfall is formed)

Answer 20

• hard rock is undercut by erosion
• it becomes unsupported and collapses
• collapsed rock is swirled around the floor
• eroding soft rock by abrasion, creating a deep plunge pool
• overtime, more undercutting causes more collapses
• and the waterfall retreats leaving a seep sided gorge