sediment

Question 1

sources of sediment (7)

Answer 1

rivers 
cliffs
long shore drift
wind
glaciers
offshore
volcanoes

Question 2

sediment cell

Answer 2

stretch of coastline usually bordered by two prominent headlands where the movement of sediment is more or less contained.

Question 3

sediment budget

Answer 3

balance between sediment being added to and removed from the coastal system

Question 4

positive sediment budget

Answer 4

more inputs than out puts
e.g more material added to the cell than removed, a net accretion of material, this is a positive budget of a surplus sediment and so shoreline builds towards the sea.

Question 5

weathering

Answer 5

break down or disintegration of rock in situ (in its original place)

Question 6

mass movement

Answer 6

when rocks loosened by weathering move down slope under influence of gravity.

Question 7

example of positive feedback involving weathering and mass movement.

Answer 7

1. weathering and mass movement
2. debris at base of cliff
3. debris removal is fast (exceeds rate of mass movement)
4. weathering and mass movement increase so less protection at base of cliff, leading to increases weathering and mass movement

Question 8

example of negative feedback involving weathering and mass movement.

Answer 8

1. weathering and mass movement
2. debris at base of cliff
3. debris removal is slow ( does not exceed rate of mass movement)
4. more protection at base of cliff, leading to decreased weathering and mass movement

Question 9

mechanical weathering

Answer 9

break up of rocks physically, examples include frost shattering, salt crystallization, wetting and drying

Question 10

frost shattering

Answer 10

1. water enters crack or joint in the rock when it rains and then freezes in cold weather. when water freezes, expands in volume by around 10%
2. expansion exerts pressure on the rock which forces the crack to widen.
3. with repeated freezing and thawing fragments of rock break away and collect at base of the cliff as scree.
4. these angular rock fragments are then use by sea as tool in marine erosion.

Question 11

salt crystallization

Answer 11

when salt water evaporates, it leaves salt crystals behind.can grow over time and exerts stresses on the rock, just as ice does, causing it to break.

Question 12

wetting and drying

Answer 12

frequent cycles of wetting and drying are common on the coast.rocks rich in clay, such as shale expand when they get wet and contract as dry, can cause them to crack and break up.

Question 13

biological weathering with examples

Answer 13

breakdown of rocks by organic activity:

1. plant roots grow into small cracks in cliff face widen as roots grow.
2. water through running decaying vegetation becomes acidic, leads to chemical
3. birds e.g puffins and animals dig burrows as so marine organisms which can also excrete chemicals.

Question 14

chemical weathering

Answer 14

chemical reaction where salts may be dissolved or a clay-like deposit may result, which is easily eroded. examples are carbonation, oxidation and solution

Question 15

carbonation

Answer 15

rainwater absorbs carbon dioxide from the air to form a weak carbonic acid .this reacts with calcium carbonate in rocks,such as limestone and chalk, to from calcium bicarbonate which is easily dissolved.the cooler the temperature of the rainwater the more carbon dioxide is absorbed so therefore more effective in winter.

Question 16

oxidation

Answer 16

reaction of rock minerals with oxygen, e.g iron to form a rusty red powder leaving rocks more vulnerable to weathering.

Question 17

solution

Answer 17

dissolving of rock materials such as halite (rock salt)

Question 18

mass movement

Answer 18

downhill movement of material under the influence of gravity

Question 19

soil creep

Answer 19

slow form of movement of individual soil particles downhill. often involves particles rising to the ground surface due to wetting or freezing and then returning vertically to the surface in response to gravity as soil dries out or thaws. occurs in wet situations.

Question 20

mud flow

Answer 20

involves earth and mud flowing downhill,usually over unconsolidated or weak bedrock such as clay, often after heavy rainfall. water gets trapped in the rock, increasing pore water pressure which forces rock particles apart and leads to slope failure. important in determining slope stability. sudden and fast flowing occurring in wet conditions.

Question 21

runoff

Answer 21

when overland flow occurs down a slope or cliff face , small particles are moved down slope to enter the littoral zone. type of flow that transfers both water and sediment. raid and wet.

Question 22

landslide

Answer 22

block of rock moving very rapidly downhill along a planar surface. moving block remains largely intact. slide movement, usually rapid and can be dry/wet

Question 23

rockfall

Answer 23

sudden collapse or breaking away of individual rock fragments.fall or bounce down slope to form scree. it s a fall which is rapid and dry.

Question 24

landslip/ slump

Answer 24

slide surface is curved rather than flat. occur in weak and unconsolidated clay and sands often when permeable rock overlies impermeable rock, which causes a build up of pore water pressure. characterized by sharp break of slope and the formation of a scar,multiple land slips can result in a terraced appearance. slide, rapid wet

Question 25

soliflucation

Answer 25

similar to soil creep but specific to cold periglacical environments. in summer, surface layer of soil thaws out and becomes extremely saturated because it lies on top of impermeable frozen ground (permafrost). known as the active layer, the sodden soil with its blanket of vegetation slowly moves downhill by flow.slow and wet.