Marine and sub-ariel processes

Question 1

What is corrasion?

Answer 1

​Sand and pebbles are picked up by the sea from an ​offshore sediment sink ​or temporal store and ​hurled against the cliffs at high tide, causing the cliffs to be eroded. The shape, size, weight and quantity of sediment picked up, as well as the wave speed, affects the erosive power of this process.

Question 2

What is abrasion?

Answer 2

A sandpaper action of rocks rubbing against the coastline which causes them to be smoothed down. Waves hurl pebbles and sand grains at the cliff face where they hammer, scrape and grind the rock

Question 3

What is attrition?

Answer 3

Wave action cause ​rocks and pebbles to hit against each other​, wearing each other down and so becoming round and eventually smaller. Involves rock fragments detached by hydraulic action or abrasion. Currents also cause rocks to swirl into each other

Question 4

What is hydraulic action?

Answer 4

As a wave crashes onto a rock or cliff face, ​air is forced into cracks, joints and faults within the rock and is trapped and compressed . As the wave retreats, the compressed air expands. The high pressure causes the ​cracks to force apart and widen when the wave retreats and the air expands. Over time this causes the rock to fracture.

Question 5

What is cavitation?

Answer 5

Bubbles found within the water may ​implode under the high pressure creating tiny jets of water that over time erode the rock.

Question 6

What is wave quarrying?

Answer 6

This is when breaking waves that hit the cliff face exert a high pressure on the rock. It is very ​similar to hydraulic action but acts with significantly more pressure to directly pull away rocks from a cliff face or scoop out smaller weathered fragments.

Question 7

What are the factors affecting erosion?

Answer 7

• Waves- Most erosion occurs during the winter months when waves are more likely to be destructive and more powerful due to frequent storms
• Beaches- If there is a beach in front of a cliff then this will ​absorb wave energy and thus reduce the effects of erosion.
• Subaerial Processes​- ​Weathering and mass movement ​processes such as landslides weaken cliffs. Rock fragments as a result of these processes may lead to increased corrasion and abrasion
• Rock Type- ​Sedimentary rocks like sandstone are made up of cemented sediment particles and are therefore are vulnerable to erosion, whereas ​igneous and metamorphic rocks are made up of ​interlocking crystals​, making them more resistant to erosion
• Rock Faults- ​Fissures, cracks and joints are are all types of weaknesses within the rock so the more there are, the quicker erosion of the rock will occur. They also i​ncrease the rock face surface area​, further promoting erosion.
• Rock Lithology- The type of rocks and the conditions of the rock’s creation directly affects its vulnerability to erosion eg. softer rock will erode more quickly

Question 8

What are the 4 main transportation processes?

Answer 8

• Suspension – Small sediment is suspended within the flow of the water.
• Saltation – Smaller sediment bounces along the sea bed
• Traction – Large, heavy ​sediment rolls along the sea bed pushed by currents.
• Solution ​– ​Dissolved material is carried within the water, potentially in a chemical form.

Question 9

What is LSD? (littoral drift)

Answer 9

• The waves hit the beach at an oblique angle determined by the direction of the ​prevailing wind
• The waves push the sediment in this direction up the beach in swash in the direction of prevailing wind
• Due to gravity, the wave then carries sediment back down the beach in backwash at a right angle
• This over time moves the sediment down the beach

Question 10

What is freeze-thaw weathering?

Answer 10

Water enters cracks in rocks and then the water ​freezes overnight during the winter. As it freezes, ​water expands by around 10% in volume which increases the pressure acting on a rock, causing cracks to develop. Over time these cracks grow, weakening the cliff making is more vulnerable to other processes of erosion

Question 11

What is salt crystallisation?

Answer 11

As seawater ​evaporates​, salt is left behind. Salt crystals will grow over time, exerting pressure on the rock, which forces the cracks to widen

Question 12

What is wetting and drying?

Answer 12

Rocks such as clay ​expand when wet ​and then contract again when they are drying. The frequent ​cycles of wetting and drying at the coast can cause these rocks and cliffs to break up

Question 13

What is carbonation?

Answer 13

Rainwater absorbs CO​2 from the air to create a ​weak carbonic acid which then reacts with ​calcium carbonate in rocks to form ​calcium bicarbonate ​which can then be easily dissolved

Question 14

What is oxidation?

Answer 14

When ​minerals become exposed to the air through ​cracks and fissures​, the mineral will become oxidised which will ​increase its volume, causing the rock to crumble. Oxidation occurs when oxygen reacts with minerals such as calcium and magnesium to form iron oxide. Iron oxide is reddish brown in colour and causes the decomposition of rock

Question 15

What is solution?

Answer 15

When rock minerals such as ​rock salt​ are dissolved

Question 16

What are the types of biological weathering?

Answer 16

• Plant Roots ​- Roots of plants growing into the cracks of rocks, which exerts pressure, eventually splitting the rocks.
• Birds ​- Some birds such as ​Puffins dig burrows into cliffs weakening them and making erosion more likely
• Decaying Vegetation - Water that flows through decaying vegetation and then over coastal areas, will be acidic, thus causing chemical weathering

Question 17

What is soil creep?

Answer 17

The ​slowest but most continuous form of mass movement involving the movement of soil particles downhill. Particles rise and fall due to ​wetting and freezing ​and in a similar way to longshore drift, this causes the soil to move down the slope.

Question 18

What is solifluction?

Answer 18

Occurs mainly in tundra areas where the land is frozen. As the top layers thaw during summer (but the lower layers still stay frozen due to permafrost) the surface layers flow over the frozen layers

Question 19

What is mudflow?

Answer 19

An increase in the water content of soil can reduce friction, leading to earth and mud to flow over underlying bedrock​, or slippery materials such as clay. Water can get trapped within the rock increasing ​pore water pressure​, which forces rock particles apart and therefore weakens the slope.

Question 20

What is rockfall?

Answer 20

Occurs on sloped cliffs when ​exposed to mechanical weathering​, though mostly occurs on ​vertical cliff faces and can be triggered by earthquakes. It leads to ​scree (rock fragments) building up at the base of the slope.

Question 21

What is a landslide?

Answer 21

Heavy rainfall leads to ​water between joints and bedding planes in cliffs which can ​reduce friction and lead to a landslide​. It occurs when a block of intact rock moves down the cliff face very quickly along a flat slope

Question 22

What is landslip/slump?

Answer 22

Contrary to a landslide, the ​slope is curved​, so often occur in weak and unconsolidated clay and sands areas. A build up in pore water pressure leads to the ​land to collapse under its own weight​.

Question 23

What is weathering?

Answer 23

The breakdown or disintegration of rocks in situ which leads to transfer and flows of material.

Question 24

Why is weathering active at the coastline?

Answer 24

Because rock faces are exposed to elements and cliff faces kept fresh by the constant removal of debris by the sea

Question 25

What is mass movement?

Answer 25

A group of processes and flows within the coastal system which transfers both energy and sediment. The sediment is an input, providing material to be transported and deposited elsewhere. It also provides an input into sediment cells. It is classified into 4 types: creep, flow, slide and fall.

Question 26

What are the aeolian transportation types?

Answer 26

• Surface creep - wind rolls/slides sand grains along the surface
• Saltation - wind is temporarily strong enough to lift grains into airflow
• Suspension - small particles are suspended in airflow