coastal zone Flashcards
What is weathering?
the breakdown of rocks where they are.
What is erosion?
When the rocks are broken down and carried away by something eg sea water.
What is mechanical weathering?
the break down of rock without changing its chemical composition.
Name one type of mechanical weathering?
Freeze-thaw weathering
What is freeze-thaw weathering?
temp alternates above and below 0*C
water gets in cracks
water freezes , rock expands, putting pressure on rock,
water thaws, rock contracts releasing pressure
repeats which causes cracks to widen and break up.
What is chemical weathering?
The breakdown of rock by changing its chemical composition.
Name a type of chemical weathering?
Carbonation weathering which happens in warm and wet conditions.
What is carbonation weathering?
Rainwater has carbon dioxide dissolved in it which makes it a weak carbonic acid.
Carbonic acid reacts with rock that contains calcium carbonate e.g carboniferous limestone, so rocks dissolve by rainwater.
What is mass movement?
shifting of rock and loose material down a slope eg cliff.
How does mass movement happen?
when the force of gravity acting on a slope is greater than the force supporting it
When is mass movement likely to happen?
When the material is full of water as it acts like a lubricant.
What does mass movement cause?
coasts to retreat rapidly.
Name two types of mass movement?
slides ( material shifts in a straight line) and slumps( material shifts with a rotation.
what are the four processes of erosion?
Hydraulic power -(waves crash against rock ,compress air which causes pressure on rocks repeats widens cracks and breaks off)
Abrasion -(eroded particles scrape/rub against rock removing small bits)
Attrition-(eroded particles in water smash into each other and break into smaller fragments)
Solution-( weak carbonic acid in seawater dissolves rock like chalk/limestone
What are the waves called that carry out erosional processes?
Destructive waves.
What is a destructive wave?
high in frequency, high and steep, more powerful backwash than swash( movement of water up the beach)
so material is removed from the coast.
Erosion by waves cause what to cliffs?
wave cut platforms.
Where does the wave erosion mostly happen?
The foot (bottom) of the cliff. first a wave-cut notch which is enlarged as the erosion continues. Rock above becomes unstable and collapses. Collapsed material washes away. the process repeat and the wave cut platform is left behind.
Where do headlands and bays form?
Where there is alternating bands of resistant and less-resistant rock along a coast.
Name one less-resistant rock?
clay. Its erodes quickly and washes away to cause a bay ( bays have a gentle slope).
Name a resistant rock?
Chalk. erodes slowly and is left jutting out forming a headland ( headlands have steep sides) can have weakness like cracks.
What can form in an eroded headland?
Caves, arches and stacks.
How is a cave formed?
Waves crash into headlands and enlarge the cracks. Repeated erosion enlarges crack to form cave
How does an arch form?
Erosion continues through cave until it breaks through the headland.Durdle door. Erosion continues until rock supporting arch collapses and leaves a stack. old Harry
What is transportation?
The movement of material by a process called longshore drift.
What is the prevailing wind? do waves follow these winds
The most common wind. yes waves follow.
Do waves hit the coast at right angles?
No oblique angles ( anything that isnt a right angle.
How does longshore drift happen?
Swash carries material up the beach in the same direction as waves. The backwash then carries material at right angle back towards the sea.
What is traction?
Traction- large particles like boulders pushed along the seabed by force of water.
what are the four processes of coastal transportation called?
Traction
suspension
saltation
solution
What is suspension?
Small particles like silt and clay are carried along the water.
What is saltation?
pebble size particles bounce along the seabed by force of water.
What is solution?
soluble materials dissolve in the water and are carried along.
What is deposition?
When the materials being carried are dropped on the coast.
What happens if deposition is greater than erosion?
Coasts are built up.
When is deposition increased?
lots of erosion elsewhere on the coast. lots of transportation of material into the area. low energy(slow) waves ( not strong enough to take alot of material away)
What are constructive waves?
Waves that deposit more material than they erode.
Info on constructive waves?
low frequency 6-8 waves per minute
low and long
powerful swash which carries material up the coast
backwash is weaker doesnt take alot of material back down.
