depositional land forms Flashcards
how do arches form?
- rocks have joints/faults which are eroded quicker forming sea caves
- this is accentuated by wave refraction which concentrates energy on the side of the headland
- line of weakness extends right through the headlands to form caves on both sides
- marine erosion deepens caves until they connect up creating complete tunnel through headland
how do stacks form?
-arch continues to widen until it is unable to support itself, roof of arch collapses falling under its own weight
through mass movement, leaving a stack which becomes detached from mainland
how do stumps form?
-stack is attacked at its base by marine erosion
-collapses to form stump
where are steep cliffs most commonly found?
in high energy environments
where are gentle cliffs most commonly found?
in low energy environments
what does the rate of retreat depend on?
- marine factors = fetch, beach, wave energy
- terrestrial factors subaerial processes, geology, rock strength
how do wave cut platforms form?
destructive waves hit against the cliff face, causing an undercut between the high and low water marks, mainly as a result of abrasion, corrosion and hydraulic action
what are spits?
narrow strips of land formed when longshore drift causes the beach to extend out to sea
what can occur when the spits from opposite sides of a bay reach out towards each other?
a double spit
what could a double spit lead to?
a barrier beach being formed
when does a barrier beach occur?
when a beach or spit extends across a bay to join two headlands
what does a barrier beach trap
water behind it
where are barrier beaches commonly formed?
in areas w low tidal ranges
why have some barrier beaches formed in the past
due to rising sea level after last glacial period when meltwater from glaciers deposited sediment in the coastal zone.
what happens when a barrier beach becomes separated from the mainland
it becomes a barrier island
