Coastal landforms
- Created by: rchapman99
- Created on: 13-11-17 20:43
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- Headlands and bays
- The soft rock is eroded quickly, forming a bay. The harder rock is eroded less and sticks out as a headland.
- Headlands and bays form where there are bands of alternating hard rock and soft rock at right angles to the shoreline.
- Coastal landforms
- Caves, aches and stacks
- When an arch collapses, it forms a stack.
- Some landforms are found in cliffs called cliff profile features.
- Caves on the opposite sides of a narrow headland may eventually join up to form an arch.
- Weak areas in rock are eroded to form caves.
- Beaches
- Beaches form when constructive waves deposit sediment on the shore; they are a store in the coastal system.
- Shingle beaches are steep and narrow. They're made up of larger particles, which pile up at steep angles. Sand beaches, formed from smaller particles, are wide and flat.
- Beaches have distinctive features. Berms are ridges of sand and pebbles found at high tide marks. Runnels are grooves in the sand running parallel to the shore, formed by backwash draining to the sea. Cusps are crescent-shaped indentations that form on beaches of mixed sand and shingle.
- Spits
- Longshore drift continues to deposit material across the river mouth, leaving a bank of sand and shingle sticking out into the sea. A straight spit that grows out roughly parallel to the coast is called a simple spit.
- Occasional changes to the dominant wind and wave direction may lead to a spit having a curved end.
- The area behind the spit is sheltered from the waves and often develops into mudflats and saltmarshes.
- Offshore bars and tombolos
- Bars are formed when a spit joins two headlands together. This can occur across a bay or across a river mouth.
- A lagoon forms behind the bar.
- Bars can also form off the coast when material moves towards the coast. These may remain partly submerged by the sea; offshore bars.
- A bar that connects the shore to an island is called a tombolo.
- Barrier islands
- Long, narrow islands of sand or gravel that run parallel to the shore and are detached from it. Form in areas where there's a good supply of sediment, a gentle slope offshore, fairly powerful waves and a small tidal range.
- Rising waters flooded the land behind beaches and transported sand offshore, where it was deposited in shallow water, forming islands.
- A lagoon or marsh often forms behind the barrier island, where the coast is sheltered from wave action.
- Sand dunes
- Formed when sand deposited by longshore drift is moved up the beach by the wind.
- Sand trapped by driftwood or berms is colonised by plants and grasses. The vegetation stabilises the sand and encourages more sand to accumulate there, forming embryo dunes.
- Over time, the oldest dunes migrate inland as newer embryo dunes are formed. These mature dunes can reach h of up to 10m.
- Estuarine mudflats and saltmarshes
- Mudflats and saltmarshes form in sheltered, low-energy environments.
- As silt and mud are deposited by the river or ide, mudflats develop.
- The mudflats are colonised by vegetation that can survive the high salt levels and long periods of submergence by the tide.
- The plants trap more mud and silt, and gradually they build upwards to create an area of saltmarsh that remains exposed for longer and longer between tides.
- Erosion by tidal currents or streams forms channels in the surface of mudflats and saltmarshes. These may be permanently flooded or dry at low tide.
- Caves, aches and stacks
- Over time, several recurved ends may be abandoned as the waves return to their original direction. A spit that has multiple recurved ends resulting from several periods of growth is called a compound spit.
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