Coastal Landforms Flashcards
What is a Geo and how do they form?
A deep and steep sided inlet, formed where waves open up a prolonged joint.
What is a blow hole, and how does it form?
A blow hole is a vertical shaft formed on a headland from a cave, in which, at high tide waves, can have air and sea spray forced through them.
What are headlands and bays and how do they form?
Headlands are protruding landscapes, consisting of more resistant rock, whereas bays are landscapes of less resistant rock, situatued inbetween headlands. These landforms only occur on discordant coastlines of differing rock resistivity.
How do the characteristics of a headland and bay differ?
Headlands are typically high energy coastlines, which are exposed to high energy processes such as hydraulic action, whereas bays are much lower energy coastlines, which allow for the deposition of sediment, sometimes deposition of sediment from the high energy headlands.
What are cliffs, headlands and bays and how are they created?
Cliffs, headlands and bays form when rocks of differing hardness are exposed together at a dicordant coastline. The tougher, more resistant rocks, (e.g granite and limestone) form headlands with cliffs, whereas weaker rocks, (e.g. clays and shales) are eroded to form sandy bars. This is due to wave refraction.
What profiles are you likely to find in a cliff?
Joints and faults are often found, caused by differing levels of tectonic activity, and widened by weathering and erosional processes. You can also find folds (sedimentary rocks squeezed by tectonic forces resulting in a bend) and dips (the titling and angling of horizontal sedimentary rocks by tectonic forces).
Why do cliffs collapse and retreat?
They collapse and retreat due to erosional and weathering processes undercutting and weakening the cliff face, slowly forming a cave at the base, which then expands, eventually unable to support the cliff’s weight, causing it to collapse. The rocks are then washed away, leaving a retreated cliff and a shore platform.
How does a headland progress from the pure headland to a stump?
The headland starts with a crack forming in the side of the headland, which slowly grows into a cave due to erosional processes and weathering. This then turns into an arch as it breaks throught the other side of the headland. Weathering then causes the top of the arch to collapse, leaving a stack, which is then slowly eroded and weathered into a stump, which then eventually is completely eroded.
Where and how do beaches form, and what determines their type?
Beaches form in low energy environments in bays, allowing for accretion of sediment. Beaches of fine sediment such as sand form the majority of the time, but in beaches where there is a strong swash, larger pieces of sediment can be collected, eventually forming a shingle beach. They can also form as sea level changes, where shingle is deposited as it falls.
What is a Berm?
A narrow shelf, path or ledge, usually at the bottom or top of a slope where the gradient is much lower, often flat.
What is a spit and how does it form?
Spits are long, narrow stretches of sand/shingle that protrude into the sea or across an estuary, and are the result of materials being moves along the coast by longshore drift, continuing to accrete in the same direction when the coastline curves; where there is an estuary. The end is also often curved where waves are refracted around the end of it into more sheltered waters behind it.
Why does a spit requrire a constant flow of sediment, and what can happen if this flow is disturbed?
If a spit does not recieve a constant flow of sediment to replenish itself, it can be eroded, and eventually breached, which can severely damage the very fragile salt marsh environment behind it.
What is an onshore bar and how does it form?
An onshore bar is formed when longshore drift deposits sediment in a spit like fashion across a bay, and connects to the other side, enclosing the bay from the ocean. The water trapped behind the bar then becomes a lagoon, often shallow with delicate environments.
What is a tombolo and how does it form?
A tombolo is formed when a spit connects the mainland to an island, this passage between the two being known as a tombolo. It is formed as the wave refraction around an obstacle such as the island offshore creates a low energy environment, allowing for the deposition of sediment.
What is a saltmarsh and how does it form?
A saltmarsh forms behind spits and bars, and is a very fragile environment that houses very fragile ecosystems. These areas are constantly flooded and drained by salt water as the tide changes, and therfore maintain a marshy waterlogged feel. These environments also allow for flocculation, usually occuring on salt marshes located over estuaries.
