Model paragraphs for most common AQA questions Flashcards
(11 cards)
Formation of a stack?
- Firstly, a crack forms in the headland due to hydralulic action and abrasion.
- Over time the crack is enlarged into a cave. Continued erosion deepens the cave until it breaks through the headland to form and arch. -
- Eventually the roof of the arch becomes unstable and collapses due to gravity and further erosion leaving a freestanding collumn of rock called a stack.
- The stack is continuallu eroded and may eventually form a stump.
Formation of a spit?
- A spit is formed by the process of longshore drift. Sediment is transported along the coastline by prevailing winds and waves.
- When the coastline changes direction such as at a river mouth, the sediment begins to deposit out into the sea.
- Over time, this builds up to form a narrow strip of land called a spit
- If wind direction changes, the end of the spit may become hooked.
- Sheltered areas behind spit allow mudflats and salt marshes to develop
Formation of a bar and lagoon
A bar is formed when longshore drift moves sediment acorss the entrance of a bay, connecting two headlands.
As the sediment builds up, it creates a bar which cuts off the bay from the sea.
This trapps water behind it forming a lagoon
Bars ususally form where there is little river input, allowing deposition to dominate over erosion.
Formtion of headlands and bays
Headlands and bays form along discordant coastlines where bands of hard and soft rock run perpendicular to the coast.
The softer rock, such as clay, erodes more quickly through processes like hydraluic action and abrasionm , forming bays.
The harder the rock, such as chalk or limestone, is more resistant and is left jutting out into the sea as a headland
Fornation of wave cut platforms
Wave cut platforms form as destructive waves erode the base of a cliff through hydralic action and abrasion. This creates a wave cut notch.
Over time, the notch deepens, and the unsupported cliff above collapses due to gravity.
This process repeats, causing the cliff to retreat inland.
As the cliff moves back, a gently sloping rocky platform is left at the base, which is called a wave-cut platform
Formation of a tombolo
A tombolo forms when a spit extends out from the mainland and connects to an island.
Longshore drift transports sediment along the coastline, and when the coastline changes direction or the wave energy decreases, deposition occurs.
Over time, the sediment builds up, linking the mainland to the island with a narrow strip of land known as a tombolo.
Formation of offshore bars
Form when waves carry sediment offshore due to backwash dragging material away from the coastline.
These bars build up underwater, parallel to the coast.
They are oftten found where waves break early, depositing sediment offshore instead of on the beach.
Offshore bars can absorb wave energy, protecting the coast behind them from erosion
Formation of barrier beaches
They form when a spit grows across a bay and joins at two headlands, emtirely cuttting off the water begind from the open sea.
As sediment continues to be depoisted by longshore drift, a long, narrow ridge of sand is built up above sea level.
Also forms a lagoon behind it.
More common in areas with low tidal ranges and large supply of sediment
Formation of islands
can form when rising sea levels flood low-lying land, leaving higher land isolated as an island.
They can also from through deposition, where sediment builds up offshore to create new land.
Erosion can sometimes seperate a former headland from the mainland, turning it into an island
Formation of sand dunes
They are formed when sand is blown inland from the beach by strong onshore winds.
When the sand encounters obstacles like driftwood or vegetation, it begins to accumulate.
Pioneer plants such as marram grass stabilise the sand with their root systems, allowing dunes to grow larger
Over time, dunes devlop in succession from embryo dunes closest to the sea to more mature dunes further inland
Formation of esturaine mudflats and saltmarshes
Mudflats from in estuariesm where river water meets the sea, in sheltered, low-energy environments.
Fine sediment brought by river settles out, creating flat, muddy areas.
Overtime, vegetation colonises the mudflats, stabilising them and encouraging further deposition.
As more sediment accumulates, the are develops into a salt marsh, with zones of different vegetation based on the frequency of tidal flooding
