2 - Coasts (Currents, tides, low/high energy coastlines) Flashcards
What are currents?
Permanent or seasonal movement of surface waters in the seas and oceans.
Explain longshore currents.
A result of wave refraction…a slight local rise in sea level = a longshore current coming from the headland, moving eroded material towards the bays = contributing to beach build-up
Explain rip currents.
A result of sandbars forming parallel to the beach. Waves have enough energy to go over the sandbar as they approach the beach but not enough energy to back over on retreat back to the sea = water trapped between beach and sandbar in the basin…eventually enough water will build up to break through the sandbar = fast flow channelled out to sea = rip current strongly sucks water out from basin into sea.
What are tides?
The periodic rise and fall of sea levels.
What causes tides?
The gravitational pull of the sun and the moon. The moon has a greater influence because it is nearer.
The moon pulls the water towards it = high tide and a compulsory bulge on the opposite side of earth.
Areas between the 2 bulges = low tide.
As the moon orbits around the earth, high tides follow it.
What is a spring tide?
Twice a lunar month, the moon and sun are positioned in a straight line so the tide raising force is strongest = highest high tide and lowest low tide.
What is a neap tide?
Twice a month, the moon and sun are positioned at 90 degree/ perpendicular to each other in relation to the earth = lowest monthly tidal range/ lowest high tide and highest low tide
Why is it important to understand the tidal range of an area?
Tidal range is a significant factor in a coastlines development as they determine the upper and lower limits of erosion and deposition.
What are the 3 conditions of an intense storm (tidal) surge?
Low pressure system (depression) allows the water level to rise, forming a bulge.
Strong winds drive the waves, pushing them towards the coastline.
Both conditions during a spring tide = more intense.
What areas in the UK are particularly at risk of storm surges and why?
The East coast of England…Kent, Essex and Norfolk due to the shape of the North Sea: the water is ‘funnelled’ as it is pushed south and concentrated into a space that is decreasing in size = water is piled up.
What is a low energy coastline, (describing its characteristics and giving examples)?
A coastline where wave energy is low.
Rate of deposition > rate of erosion.
Landforms include beaches and spits.
Examples are estuaries, inlets and sheltered bays.
What is a high energy coastline, (describing its characteristics and giving examples)?
A coastline where wave energy is high.
Rate of erosion > rate of deposition.
Landforms include headlands, cliffs and wave-cut platforms.
Examples are the exposed Atlantic coasts of North Europe, North America and the North Cornish Coast of SW England.
