Coastal landforms Flashcards
Difference between soft and hard rock
Hard rock is like granite take a long time to erode, while softer rocks like sandstone erode more quicker
Rocks with lots of joints and faults (cracks and weaknesses in the rock) erode faster
How are discordant coastlines made up?
They are made up of alternating bands of hard and soft rock at right angle to the coast
Rain
How are concordant coastlines made up?
The alternating bands of hard and soft rock are parallel to the coast
sandwich
Where do headland and bays form?
They form along discordant coastline (rain) the less resistant rock is eroded faster, forming a bay with a gentle slope
How are caves, arches and stacks formed?
The resistant rock that makes up headlands often has weakened like cracks
Waves crash into the headland and enlarge the cracks (mainly by hydraulic action and abrasion)
Repeated erosion and enlargement of the cracks causes a cave to form
Continued erosion deepens the cave untill it breaks throughthe headland to form an arch
Till erosion continues to wear away the rock supporting the arch, untill it eventually collapes forming an stack
How are wave-cut platforms formed?
Repeated erosion causes the rocks above the notch to become unstable and it eventually collapses
The collapsed material is washed away and a new wave-cut notch starts to form
After repeated collapses the cliff retreats, leaving a wave-cut platform
How are sand beaches created?
Sand beaches are created by low energy waves and are flat and wide - sand particles are small so the weak backwash can move them back down the beach creating a long gentle slope
How are shingle beaches created ?
Shingle beaches are created by high energy waves and are steep and narrow - snad particles are washed away but lsrge shingle is left behind
The shingle particles build up a steep slope
How are beaches created?
They are formed by constructive waves (depositing material)
Beaches are found on coasts between the highand low water marks
Spits
Spits form at sharp bends in the coastline (rivermouth)
Longshore drift transports sand and shingle past the bend and deposits it in the sea
Strong winds and waves can curve the end of the spit (forming a recurved end)
The area behind the spit is sheltered from waves, so material accumulates and plants are able to grow.
Over time, the sheltered area can become a mud flat
Bars
A bar forms when a split joins two headland together
The bay between the headlands gets cut off from the sea
This means a lagoon can form behind the bar
Offshore bars can form if the coast has a gentle slope - friction with the sea bed causes waves to slow down and deposit sediment offshore creating a bar that is not connected to the coast
Sand dunes
Sand dunes are formed when sand deposited by longshore drift is moved up the beach by the wind
Obstacles cause wind speed to decrease so sand is deposited, forming small embryo dunes
Embryo dunes are colonised by plants
The roots of the vegetation stabilise the sand, encouraging more sans to accumulate there. This forms foredunes and, eventually, mature dune. New embryo dunes form in front of stabilised dunes
Dune slacks (small pools) can form in hollows between dunes
