coats Flashcards
how do waves form
by winds blowing over the sea. friction with the surface of the water causes ripples that develop into waves. tsunamis form when earthquakes or volcanic eruptions shake the sea bed.
the distance that wave-generating winds blow across the water is called the fetch
what happens when waves reach the coast
in the open sea, there is little horizontal movement of water
circular orbit in open water
friction with seabed distorts circular motion
increasing elliptical orbit as water becomes shallower, and waves move forward.
the wave breaks and collapses onto the beach.
water returns as backwash
water rushes up beach as wash
define and describe constructive waves
formed by storms often hundreds of kilometers away. common in summer
low waves with wave crest far apart. gently sloping wavefronts. breaking wave push large amounts of sand and pebbles up the beach
define and describe destructive waves
formed by local storms close to the coast. common in winter
waves close together. waves become high with a steep wavefront. breaking waves plunging down onto the beach with little forward swash
wrong backwash erodes sand and pebbles and can destroy the beach
Erosion
The breakdown and transport of rocks
Attrition
Rocks that bash together to become smooth/smaller
Solution
A chemical reaction that dissolves rocks
Abrasion
Rocks hurled at the base of a cliff to break pieces apart
Hydraulic Action
Water enters cracks in the cliff, the air compresses, causing the crack to expand.
Types of Erosion
Attrition
abrasion
Hydraulic Action
Solution
Types of Transportation
Solution
suspension
traction
saltation
transportation
A natural process by which eroded material is carried/transported.
Solution
Minerals dissolve in water and are carried along.
Suspension
Sediment is carried along in the flow of the water.
Saltation
Pebbles that bounce along the sea/river bed
Traction
Boulders that roll along a river/sea bed by the force of the flowing water
Mass Movement
A large movement of soil and rock debris that moves down slopes in response to the pull of gravity in a vertical direction
Mass Movement steps
1 Rain saturates the permeable rock above the impermeable rock making it heavy.
2 Waves or a river will erode the base of the slope making it unstable.
3 Eventually, the weight of the permeable rock above the impermeable rock weakens and collapses.
4 The debris at the base of the cliff is then removed and transported by waves or a river.
What is Deposition?
When the sea or river loses energy, it drops the sand, rock particles, and pebbles it has been carrying. This is called deposition.
Deposition happens when the swash is stronger than the backwash and is associated with constructive waves.
Types of Weathering
Carbonation
mechanical
Carbonation
The weathering of rocks by chemicals is called chemical weathering. Rainwater is naturally slightly acidic because carbon dioxide from the air dissolves in it. Minerals in rocks may react with the rainwater, causing the rock to be weathered
Mechanical
Mechanical weathering is caused by physical changes such as changes in temperature, freezing and thawing.
Water gets into cracks in rocks, freezes when the temperature drops below 0’c, prising the rock apart. When the water melts, a larger crack develops. Over time this causes rocks to break apart.
Formation of Coastal Spits -Deposition
1) Swash moves up the beach at the angle of the prevailing wind.
2) Backwash moves down the beach at 90° to the coastline, due to gravity.
3) Longshore Drift transports material along the beach.
4) Deposition causes the beach to extend, until reaching a river estuary.
5) Change in prevailing wind direction forms a hook.
6) Sheltered area behind spit encourages deposition, salt marsh forms.
Formation of Bays and Headlands
1) Waves attack the coastline.
2) Softer rock is eroded by the sea quicker forming a bay, calm area causes deposition.
3) More resistant rock is left jutting out into the
sea. This is a headland and is now more vulnerable to erosion.
Freeze-thaw weathering stage one
Water seeps into cracks and fractures in the rock.
Freeze-thaw weathering stage two
When the water freezes, it expands about 9%. This wedges apart from the rock
freeze-thaw weathering stage three
With repeated freeze-thaw cycles, the rock breaks off.
what does the size of a wave depend on
Fetch How far the wave has travelled
• Strength of the wind.
• How long the wind has been blowing for
Formation of Coastal Stack
1) Hydraulic action widens cracks in the cliff face
overtime.
2) Abrasion forms a wave-cut notch between HT and
LT.
3) Further abrasion widens the wave-cut notch from a cave.
4) Caves from both sides of the headland break through to form an arch.
5) Weather above/erosion below –arch collapses
leaving stack.
6) Further weathering and erosion eaves a stump.
Describe how a wave-cut platform is formed?
The sea attacks the base of the cliff-forming a wave-cut notch.
The notch increases in size causing the cliff to collapse.
The backwash carries the rubble towards the sea forming a wave-cut platform.
The process repeats and the cliff continues to retreat.
