coasts Flashcards
(68 cards)
wave length
horizontal distance between crests
crest
top of a wave
trough
bottom of a wave
wave height
the vertical distance to the crest
wave frequency
number of waves breaking per minute
fetch
distance the wave has travelled uniturrupted over open water
swash
the water moving up the beach by energy from the wind
backwash
the wave moving back down the beach under the influence of gravity
characteristics of a constructive wave
long wave length
low frequency
low wave (under 1m)
wave front gently sloping
gains little height then breaks and slpis onto the beach
low energy
strong swash
weak backwash
characteristics of a destructive wave
high energy
steep wave front
wave height over 1m
gains height
restricted swash
strong backwash
plunges onto the beach so doesnt travel far
reasons why some waves are stronger than others
-how long the wind has been blowing (more energy transfered)
-speed of the wind, strong winds result in stronger waves as more energy is tranferred
-fetch as the longer the fetch the larger the possibility of large waves
what is weathering
breaking down of rocks by the action of the weather, can be physical or chemical
what is mechanical weathering
disintergration of rocks and is associated with extremes of temp and water. the rock is broken down without its chemical composition changing
what are the 2 main types of mechanical weathering
freeze thaw and salt weathering
what is freeze thaw
occours when it rains in places where it is very cold. When it rains in the day water gathers in cracks in the cliff. At night when temps drop the water freezes and expands by 9%. This freezing and thawing repeats making cracks bigger putting pressure on surrouding rocks. this causes rocks to break off from the cliff
what is salt weathering
when salt spray gets into cracks in cliffs, the water evaporates leaving behind salt which crystalises putting pressure on the surrounding rocks and weathering the structure
what is chemical weathering
Happens when a chemical reaction causes the rock to decompose/break up
rainwater mixes with carbon dioxide in the air the rain water then becomes a weak carbonic acid this acid then attacks the alkaline rocks especially chalk on limestone. The Rock is slowly dissolved by the acid and weakened over time
How does Mass movement happen
Mass movement is the downslope movement of rock soil or mud under the influence of gravity heavy rainfall usually triggers this
What is Rock fall
Fragments of rock breakaway from the cliff face due to weathering EG freeze thaw
what is slide (mass movement)
blocks of rock slide downhill
what is a slump (mass movement)
saturated soil slumped along a curved surface
What is DEPOSITion
Deposition is where the waves break and leave behind material they were transporting deposition results in more sediments staying on the beach then is taken away by the backwash
What is erosion
Erosion is the wearing wave rocks and on the coastline by the action of water or the wind this material is then transported
Why does deposition happen
Coastal deposition takes place in areas where the flow of water slows down waves loose energy and are no longer able to transport material