Coasts Eq2 Flashcards
What are constructive waves
Low height, long wavelength, strong swash (the forward movement of a wave up a beach), weak backwash (the backward movement of a wave down a beach), pushes sediment up creating a ridge
What are destructive waves
High waves height, short wavelength, strong backwash, weak swash, so sediment is eroded and carried creating an offshore ridge
What is hydraulic action
Sheer force of water crashing against the coastline causing material to be dislodged and carried away
What is corrosion
Process of chemical erosion, occurs in limestone
What is attrition
When material such as rocks and stones carried by waves hit and knock against each other, wearing them down
What is abrasion
When rocks and other materials carried by the sea are picked up by strong winds and thrown against the coastline causing more material to be broken off and carried away by the sea
Wave cut notches
Curved indentation 1-2 metres high extending along the base of a cliff, as a result of abrasion, hydraulic action, and sometimes corrosion between high and low tide marks
Wave cut platforms
Flat rock surface exposed at low tide, extending out to sea from the base of a cliff, occurs when a wave cut notch forms and the rock above collapses
What is cave-arch-stack-stump
Cracks are formed in rock due to abrasion, when waves force themselves into the cracks, caves are formed,when this continues to the other side, arches are formed, when the material above an arch collapsed, stacks are formed, and then when this erodes, stumps are formed
What is a cliff
Vertical, or near vertical, or sloping wall of rock or sediment that borders the sea, angle of slope differs due to rock structure and geology, though the processes that act on them are the same
What is traction
Large material rolling or sliding along the seabed
What is saltation
Sand and small sediment bounces along the seabed
What is suspension
Lighter, finer sediment is carried within the water
What is solution
Ions dissolved in the water
What is longshore drift
Waves approach the coast at an angle due to prevailing wind, the swash pushes the sediment up the beach at an angle, the backwash pulls the sediment down, causing it to move in a zigzag pattern, this results in the net movement of sediment along the beach
What is wave refraction
When waves approach shallow water and slow down due to friction, waves in the bays continue to move at the same rate, which concentrates energy to the headlands, increasing erosion and spreads out energy in the bay, increasing deposition
What is a spit
When a beach extends along a curve in the coastline, the longshore drift current loses energy, causing deposition
What is a swash aligned shoreline
When waves approach the beach parallel to the shoreline, so longshore drift is limited
What is a drift aligned shoreline
When waves approach the beach at an angle, so there is consistent longshore drift
What is a cuspate foreland
Triangular shaped feature extending out from shoreline, caused by opposing longshore drift directions
What is a bar
A bridge connecting two areas of land, with a shallow lagoon behind it
What is a tombolo
A bar that attaches to an offshore island, caused by wave refraction around the island which leads to deposition
What is a bayhead beach
Swash aligned beach where waves move sediment into a bay
What is gravity settling
Energy of waves is not great enough to transport sediment, so larger material settles first, followed by smaller material
What is flocculation
Very fine particles like clay ‘clump’ together due to electrostatic attraction and then, when they have formed larger particles, they sink
What is an example of a sediment cell
Flamborough head to the wash
2 examples of mechanical weathering
Freeze thaw (water expands when it freezes and exerts mechanical force on the rocks surrounding it), exfoliation (sometimes referred to onion skin weathering, when sheets or layers of rock split off due to differential thermal expansion)
2 examples of biological weathering
Burrowing - when worms and vertebrate animals burrow and bring rocks to the surface allowing chemical weathering to occur at a greater depth
Root action - causes mechanical and chemical weathering of rock due to wedging action of plant roots that grow along joints and bedding planes
1 examples of chemical weathering
Carbonation - occurs in limestone coasts, sea water reacts with limestone and forms acid, which washes away
What is rock fall
Fragments of rock break away from the cliff face due to weathering
Occurs where there is more brittle, resistant rock, usually results in steep cliff profiles,
What is a landslide
Blocks of rock slide down the hill
Occurs frequently when strata are dipping towards the coast, rock with joints are more vulnerable, results in a sloping cliff profile
What is a mudslide
Saturated soil flows down a slope
Occurs in unconsolidated material that is saturated with water, results in sloping cliff profiles
What is slumping
Saturated soil slumps along a curved surface
Occurs in unconsolidated sediment, especially when wet, results in step-like cliff profile
What is meant by dynamic equilibrium
Coastal systems are always trying to reach a balance point between the amount of energy in an area and the amount of sediment
E.g in winter, storms create destructive waves which forms an offshore ridge, in summer the offshore bar creates a barrier, forming constructive waves which bring sediment back up the beach
