coasts Flashcards
features of destructive waves
high frequency
high
steep
features of constructive waves
low frequency
low
long
destructive waves
backwash is more powerful than swash so material is removed
how do constructive waves build beaches
swash is more powerful than backwash so material is deposited
mechanical weathering
breakdown of rock without changing it’s chemical composition
e.g. freeze thaw weathering
chemical weathering
breakdown of rock by changing its chemical composition
e.g. carbonation weathering
process of freeze-thaw weathering (mechanical)
- water enters rock that has cracks
- it freezes overnight which makes the crack bigger
- in the day, it melts and more water fills into the crack
- the water freezes again making the crack bigger
- this repeats until the rock breaks
process of chemical weathering
- rainwater has carbon dioxide dissolved in it —> makes it a weak carbonic acid
- carbonic acid reacts with limestone —> so rocks break
define hydraulic action
waves crash against rock and pushes air into cracks —> the force of this causes bits of rock to break off
define abrasion
loose rocks (sediment) are thrown against the cliff by waves. this wears away at the cliff and chips bits of rock
define attrition
eroded particles in water collide and knock into each other to become smaller and more rounded
define solution
seawater dissolves material from the rock
what is mass movement
shifting of rocks and loose material down a slope e.g. a cliff
why does mass movement happen
it happens when the force of gravity acting on a slope is greater than the force supporting it
define slide
material shifts in a straight line along a slide plane
define slump
material rotates along a curved slip plane
define rockfall
material breaks up and falls down a slope
3 types of mass movement
slides
slumps
rockfall
describe longshore drift
- waves follow the direction of the prevailing wind and approach beach at an angle
- swash carries material up the beach at the same angle
- backwash carries material straight back down the beach at right angles
- overtime, material moves along beach in zigzag pattern
define deposition
when water loses energy and drops the material it is carrying
when does deposition on an area of a coast increase?
there’s lots of erosion elsewhere (so more material is available)
how do headlands and bays form
- alternating bands of resistant and less resistant rock
- less resistant rock is eroded faster, forming a bay
- resistant rock erode more slowly and forms a headland which sticks out
forms along discordant coastlines