2.2.1 Coastal landforms

Question 1

What are the erosional landforms?

Answer 1

• Cliffs
• Wave-cut notch/platform
• Headlands
• Bays
• Caves, Arches and Stacks

Question 2

Examples for each erosional landform

Answer 2

• Cliffs: Flamborough Head in Yorkshire
• Wave-cut notch/platform: Flamborough Head in Yorkshire
• Headlands: Swanage on the South Coast of England
• Bays: Robin Hood’s Bay, North East
• Caves, Arches and Stacks: Durdle Door in Dorset.

Question 3

What are the depositional landforms?

Answer 3

• Beaches
• Spits
• Offshore Bars
• Tombolos
• Barrier islands
• Sand dunes
• Estuarine Mudflats
• Saltmarshes

Question 4

Examples for each depositional landform

Answer 4

• Beaches
• Spits: Hurst Spit, New Forest
• Tombolos: Lindisfarne in Northumberland. | St Ninian’s Isle in Shetland
• Barrier islands: Start Bay in Devon
• Sand dunes: Studland in Dorset

Question 5

Halophytes

Answer 5

Plants which can tolerate salt water.

Question 6

Xerophytes

Answer 6

Plants which can tolerate very dry conditions.

Question 7

Formation of a cliff and wave-cut platforms

Answer 7

Cliffs form as the sea erodes the land. Over time, cliffs retreat due to the action of waves and weathering.

Weathering and wave erosion cause a notch to form at the high water mark. This eventually develops into a cave.

Rock above the cave becomes unstable with nothing to support it, and it collapses.

Wave-cut platforms are flat surfaces left behind when a cliff is eroded.

Question 8

Formation of headlands and bays

Answer 8

Headlands and bays form where there are bands of alternating hard rock and soft rock at right angles to the shoreline.

The soft rock is eroded quickly, forming a bay. The harder rock is eroded less and sticks out as a headland.

Question 9

Caves, arches, stacks and stumps

Answer 9

Weak areas in rock (e.g. joints) are eroded to form caves.

Caves on the opposite sides of a narrow headlands may eventually join up to form an arch.

When an arch collapses it forms a stack.

Question 10

Coves

Answer 10

Coves are formed on resistant rock coastlines (concordant). Erosion occurs in an area of resistant rock and a weakness if punctured in the rock, causing rapid erosion of the soft rock behind it. This creates a cove, often with sandy beaches.

For example, Lulworth Cove, Dorset, UK

Question 11

Formation of a beach

Answer 11

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.

Question 12

Describe the features of a beach

Answer 12

Berms and ridges of sand and pebbles (about 1-2m high) found at high tide marks.

Runnels are grooves in the sand running parallel to the shore, formed by backwash draining to sea.

Cusps are crescent-shaped indentations that form on beaches of mixed sand and shingle.

Question 13

Formation of a spit

Answer 13

Spits tend to form where the coast suddenly changes direction - e.g. across river mouths.

1) Longshore drift continues to deposit material across the river mouth, leaving a bank of sand and shingle sticking out into the sea.

2) Occasional changes to the dominant wind and wave directions may lead to a spit having a curved end (sometimes known as a recurved end).

3) Over time, several recurved ends may be abandoned as the waves return to their original direction.

4) The area behind the spit is sheltered from the waves and often develops into mudflats and saltmarshes.

Question 14

Different types of spits

Answer 14

• A straight spit that grows out roughly parallel to the court is called a simple split.
• A spit that has multiple recurved ends resulting from several periods of growth is called a compound spit.

Question 15

Formation of offshore bars and tombolos

Answer 15

1) Bars are formed when a spit joins two headlands together. This can occur across a bay or across a river mouth.

2) A lagoon forms behind the bar.

3) Bars can also form off the coast when material moves towards the coast (normally as sea level rises). These may remain partly submerged by the sea - in this case they’re called offshore bars.

4) A bar that connects the shore to an island is called a tombolo.

5) For example, St Ninian’s Isle in the Shetland Islands is joined to a larger island by a tombolo.

Question 16

Formation of barrier islands (barrier beach)

Answer 16

Barrier islands (or barrier beaches) are long, narrow islands of sand or gravel that run parallel to the shore and are detached from it. They tend to form in areas where there’s a good supply of sediment, a gentle slope offshore, fairly powerful waves and a small tidal range.
It isn’t clear how they form, but scientists believe they probably formed after the last ice age ended, when ice melt caused rapid sea level rise. The rising waters flooded the land behind beaches and transported sand offshore where it was deposited in shallow water, forming islands.

A lagoon or march often forms behind the barrier island, where the coast is sheltered from wave action.

Barrier islands are found on many coastlines, including the east coast of the USA. e.g. Horn Island in Mississippi.

Question 17

Formation of sand dunes

Answer 17

1) Sand dunes are formed when sand deposited by longshore drift is moved up the beach by the wind.

2) Sand trapped by driftwood or berms is colonised by plants and grasses, e.g. marram grass. The vegetation stabilises the sand and encourages more sand to accumulate there, forming embryo dunes.

3) Over time, the oldest dunes migrate inland as newer embryo dunes are formed. These mature dunes can reach heights of up to 10m.

Question 18

Formation of estuarine mudflats and saltmarshes

Answer 18

1) Mudflats and saltmarshes form in sheltered, low-energy environments, e.g. river estuaries or behind spits.

2) As silt and mud are deposited by the river or the tide, mudflats develop.

3) The mudflats are colonised by vegetation that can survive the high salt levels and long periods of submergence by the tide.

4) 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.

5) Erosion by tidal currents or streams forms channels in the surface or mudflats and saltmarshes. These may be permanently flooded or dry at low tide.

Question 19

Plant Succession

Answer 19

A directional change in the types of plant species that occupy a given area through time. It involves the processes of colonisation, establishment and extinction.

Question 20

Sand dunes

Answer 20

Small ridges or hills of sand found at the top of a beach above the usual maximum reach of the waves.

Question 21

Psammosere

Answer 21

An ecological succession that began life on newly exposed coastal sand. The most common psammoseres are sand dune systems.

Question 22

Climax vegetation

Answer 22

The dominant mix of vegetation species that characterise an environment given time for colonisation to occur and reach stability.

Question 23

Conditions for sand dunes to develop

Answer 23

• Large sandy beaches
• Large tidal zone exposing a large beach
• Persistent onshore winds to dry and move the sand parties by saltation inland
• Shallow beach gradient (providing good conditions for sediment transport).

Question 24

Example of Sand dunes

Answer 24

Studland in Dorset

Question 25

Embryo dunes

Answer 25

• Youngest dune, at the front.
• “Pioneer species” colonise the dune.
• Salinity, lack of humus and pH of 8-9 make it a hostile environment.
• Vegetation needs a high salt tolerance (halophytes).
• Only 20% vegetation cover.
• Couch grass.

Question 26

Fore dunes

Answer 26

• Slightly higher and older dunes
• 20% visible sand
• Marram grass dominates
• Long roots which can reach deep groundwater stores
• These stems help to stabilise the sound.
• Embryo dunes alter environments allowing other species to colonise the area.

Question 27

Yellow dunes

Answer 27

• Highest point of the dune, well above tide level.
• More plant species can colonise due to less alkalinity and better water retention.
• Marram grass stabilises the sand due to its deep vertical root system.

Question 28

Grey dunes

Answer 28

• Much more stable, mosses and lichens fill the few remaining spaces between plants so that vegetation cover is 90-100%.
• Marram grass is now less common.
• Small shrubs appear for the first time.
• “Fixed dune” = sand not transported.
• Thin layer of humus is developed as plants die and decay. The moisture and nutrients present in the humus assists in the colonisation of this part of the dune.

Question 29

Dune slacks

Answer 29

• Occur in low lying allows between dune ridges.
• High water table attracts moisture loving plants.
• Spol acidic
• Vegetation cover almost complete
• Soil starts to develop

Question 30

Heath/woodland

Answer 30

• The end result of succession is a climate climax community.
• This last stage of plant succession is called climax vegetation and is rarely reached.
• The climactic community is known as a psammosere.
• Sheltered dune with minimal influence from the coast.