Topic3(3)-Coastal Landforms

Question 1

Cliffs and wave-cut platforms

-how are they formed

Answer 1

• Cliffs form as sea erodes the land
• over time, cliff retreats due to the action of waves and weathering
• weathering and wave erosion causes a notch at higher water mark, developing into a cave
• rocks above cave become unstable, so collapses
• wave-cut platforms and flat surfaces are left behind when cliff is further eroded

Question 2

Headlands and Bays

-how do they form

Answer 2

• when there are bands of alternating soft and hard rock at right angles to the shoreline
• soft rock is eroded quickly,forming a bay
• hard rock is eroded less and sticks out as a headland

Question 3

Caves, arches and stacks

-how are they formed

Answer 3

• they are cliff profile features
• weak areas in rock are eroded to form caves
• caves on opposite sides of a narrow headland may eventually join up to form an arch
• when an arch collapses it forms a stack

Question 4

Name 3 sets of coastal landforms caused by erosion

Answer 4

1) cliffs and wave cut platforms
2) bays and headlands
3) caves, arches and stacks

Question 5

Name 6 sets of coastal landforms caused by deposition

Answer 5

1) beaches
2) spits
3) offshore bars and tombolos
4) barrier island
5) sand dunes
6) estuarine mudflats and saltmarshes

Question 6

Beaches

• how are they formed
• features

Answer 6

• formed when constructive waves deposit sediment on the shore (store)
• Berms and Ridges of sand and pebbles are found at high tide marks
• Runnels are grooves in the sand running parallel to shore, formed by backwash draining to the sea
• Cusps are crescent-shaped indentations that form on both beach types

Question 7

What are the 2 types of beach?

Answer 7

1) Shingle beaches

2) Sand beaches

Question 8

Shingle beaches

Answer 8

• steep and narrow

- made up of larger particles (piled at steeper angles)

Question 9

Sand beaches

Answer 9

• formed from smaller particles

- wide and flat

Question 10

Spits

-how are they formed

Answer 10

• tend to form where the coast suddenly changes direction
• longshore drift continues to deposit material across river mouth, leaving a bank of sand and shingle sticking out to sea
• occasional changes in dominant wind and wave direction may lead to curved end
• the area behind the spit is sheltered from waves so often develops into mudflats and saltmarshes

Question 11

What are the two types of Spits

Answer 11

1) Simple spits (no recurved end) just straight

2) Compound spits(multiple recurved ends)

Question 12

Offshore bars and tombolos

-how are they formed

Answer 12

• bars are formed when a spit joins 2 headlands together (can occur over a bay or river mouth)
• a lagoon forms behind a bar
• bars can also form off the coast when material moves towards the coast (as sea level rises)
• these may remain partially submerged so would be called offshore bars

Question 13

What is an offshore bar

Answer 13

Bars which form off the coast and remain partially submerged by the sea, usually due to sea level rise

Question 14

What is a tombolo

Answer 14

A bar that connects the shore to an island (often a stack)

E.G. St Ninians Isle in the Shetland Islands

Question 15

Barrier islands (Barrier beaches)
-what are they

Answer 15

-long, narrow islands of sand or gravel that run parallel to the shore and are detached
-tend to form in areas with a good sediment supply, a gentle slope offshore, fairly powerful waves and a small tidal range
E.G. Horn Island in Mississippi, USA

Question 16

Theories of how barrier beaches are formed

Answer 16

• scientists think they probably formed after the last ice age ended, when ice melt caused rapid sea level rise
• the waters flooded the land behind beaches and transported sand offshore, where it was deposited in shallow water, forming island
• another theory is the islands were originally bars which were eroded in sections

Question 17

What is normally found behind a barrier beach

Answer 17

Lagoons or marshes (sheltered)

Question 18

How are Sand dunes formed

Answer 18

• when sand deposited by longshore drift is moved up the beach by wind
• sand is trapped by driftwood/berms and colonised by plants and grasses e.g. marram grass
• vegetation stabilises sand and encourages more sand to accumulate there, forming embryo dunes

Question 19

Where do the oldest dunes migrate?

Answer 19

Inland, as newer embryo dunes are formed. These mature dunes can reach heights of up to 10m

Question 20

Where do Estuarine mudflats and saltmarshes form?

Answer 20

In sheltered, low-energy environments (e.g. behind spits, river estuaries)

Question 21

How are mudflats formed

Answer 21

Silt and mud are deposited by the river or tide.

Question 22

What does vegetation colonising do to mudflats

Answer 22

Allows them to survive high salt levels and long periods of submergence by the tide

Question 23

How do saltmarshes form

Answer 23

Plants which colonise mudflats trap more mud and silt, and gradually build up to create an area of saltmarsh that remains exposed for longer between tides

Question 24

What can erosion do to mudflats and saltmarshes

Answer 24

Erosion from currents or streams form channels

These may be permanently flooded or dry at low tide