coastal processes Flashcards
what are the six main ways that waves erode the cliff
abrasion, hydraulic action, cavitation, wave quarrying, corrosion, attrition
what is abrasion
abrasion (corrasion) is where bits of rock and sediment transported by the waves smash and grind against rocks and cliffs, breaking bits off and smoothing surfaces
what is hydraulic action
air in cracks in cliffs is compressed when waves crash in. the pressure which is exerted by the compressed air breaks off rock pieces
what is cavitation
as the waves recede, the compressed air expands violently, again exerting pressure on the rock and causing pieces to break off
what is wave quarrying
the energy of a wave as it breaks against a cliff is enough to detach pieces of rock
what is solution
solution (corrosion) is where soluble rocks get gradually disolved by seawater
what is atrrition
bits of rock smashing into each other that then break into smaller bits
what are the four main processes of transportation
- solution
- suspension
- saltation
- traction
what is solution (transportation)
substances that are able to dissolve are carried along by the water, e.g. limestone
what is suspension
where very fine material like silt and clay particles are whipped up by turbulence and carried along in the water, most kinds of eroded material is transported in this way
what is saltation
where the larger particles like pebbles and gravel are too heavy to be transported through suspension so the force of the water causes them to bounce along the seabed
what is traction
where very large particles like boulders are pushed along the seabed by the force of the water
what is longshore drift (littoral drift)
where the swash carries the sediment up the beach parallel to the prevailing wind, the backwash then carries the sediment back down the beach at a right angle to the shoreline.
what is deposition
where the material being transported is dropped on the coast
what is marine deposition
where sediment being carried by the seawater is being dropped along the coast
what is aeolian deposition
where sediment being carried by the air is deposited
why does deposition occur
when the sediment load exceeds the ability of the water or wind to carry it, this can be either because the sediment load has increased or the wind or water flow is slowing down
why does wind or water slow down
- due to the increase in friction:
-waves coming into shallow water or wind reaches the land, causes friction with ground surfaces which slows them down - due to the flow becoming turbulent:
-if the water or wind encounters an obstacle the flow becomes rougher and overall speed decrease - if the wind drops then the wave height, speed and energy will decrease as well
what are the types of sub-aerial weathering
mechanical, biological, chemical
what are the types of mechanical weathering
freeze thaw, salt weathering, wetting and drying
what is freeze thaw weathering
- occurs when temperatures fluctuate above and below freezing
- water enters the joints and crevices in rocks
- if temperature drops below 0 degrees the water freezes and expands
- over time this repeated freeze thaw action weakens the rock, causing parts to break off
what is salt weathering
- caused by saline water
- saline water enters pores or cracks in the rocks during high tide
- as the tide goes out then the rocks dry and water evaporates causing salt crystals to form, when they form they expand which causes pressure on the rocks, meaning that pieces break off
what is wetting and drying
some rocks along the coast contain clay, when the clay becomes wet it expands which causes fragments to break off
what is chemical weathering
it is the breakdown of rock through changing its chemical composition. e.g. carbon dioxide in the atmosphere dissolves into the rainwater which creates a weak carbonic acid, this acid reacts with rock that contains calcium carbonate (limestone) and the rocks gradually dissolve
