Coastal Landforms Flashcards
Constructive/spilling waves
Deposits sand onto a gently sloping beach (begin breaking motion far from shore and lose energy when it reaches land)
Destructive/plunging waves
Hits steeply sloped beaches with great force, taking back much of the sand (may erode the beach)
Swash
The movement of sand, silt, and water driven onto the beach caused by wave action
Backwash
Water returning to the ocean by force of gravity
Longshore drift
The horizontal movement of sediment along a beach caused by waves and currents
Which processes cause shoreline erosion?
Corrosion (dissolved by sea water), abrasion (sand and sediment carried by water wear down rock surfaces and leave them smooth), attrition, hydraulic action (waves drive water into cracks in the rocks, breaking it apart)
How does air increase the work of hydraulic action?
As waves hit the rocks, compressed air is driven into the cracks, vibrating the rock face, which helps to disintegrate the rocks
Why are rocky ocean cliffs often so steep?
Undercutting - the action of waves that break away rock at water level, causing the cliff to lose support and collapse
(As rock is cracked and worn down by hydraulic action)
Where does sand that is deposited onto beaches come from?
Sediment (sand, clay, silt) from eroded cliffs is carried along by longshore drift
Describe the formation of caves and blowholes when cliffs retreat
Caves surface along the cliff. Hydraulic action enlarges the cliffs until support is lost and it collapses into the sea.
Blowholes form when the roof of a cave originally carved out by abrasion and hydraulic action collapses. Water goes through and up the blowhole like a whale.
Bays and headlands
Bays form as shorelines erode and softer rock (clay/sand/gravel) wears away faster than the hard rock > the hard rock that resists erosion forms headlands
What kind of erosional features come from the headlands?
Caves will form first, and they’ll get larger and deeper until they join together with a cave on the other side of the headland, creating a tunnel.
When the tunnels increase in size, they’ll form arches.
The arches will grow until support is lost and the sides will be left standing - stacks.
What are wave-cut platforms?
They are the flat, rocky remains of the original headlands and are an accumulation of sand and rocks. They form when undercutting occurs and the cliff has collapsed into the sea, leaving behind a flat platform
Spit
A long depositional feature of sediment created by longshore drift
Tombolo
A ridge of sand joining an island to the mainland created by longshore drift
