COASTAL SYSTEMS AND LANDSCAPES CGP - Coastal Landforms

Question 1

Coastal landform caused by erosion

Answer 1

Cliffs and wave cut platforms
Headlands and bays
Caves, arches and stacks

Question 2

Cliff and wave-cut platform formation

Answer 2

Form as sea erodes the land. Overtime, cliffs retreat due to action of waves and weathering. Weathering and wave erosion cause notch to form at high water mark (eventually develops into cave). Rock above notch/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 3

Where do headland and bays form? And how?

Answer 3

Where there are bands of alternating hard rock and soft rock at right angles to the shoreline
Soft rock is eroded quickly, forming bay. Harder rock eroded less and sticks out as headland.

Question 4

What are landform that are found in cliffs called? E.g.

Answer 4

Cliff profile features. Caves, arches, stacks

Question 5

How are caves, arches, stacks and stumps formed?

Answer 5

Weak areas in rock (e.g. joints) are eroded to form caves.
Caves on opposite sides of headland may eventually join up to form an arch.
When each collapses it forms a stack.
Continued weathering and erosion causes top of stack to collapse to from stump.

Question 6

What six coastal landforms are formed by deposition?

Answer 6

Beaches
Spits
Offshore bars and tombolos
Barrier islands
Sand dunes
Estuaries and salt marshes

Question 7

When are beaches formed? What are they in the system?

Answer 7

When constructive waves deposit sediment on the shore. A store in coastal system.

Question 8

What are shingle beaches like?

Answer 8

Steep and narrow. Made up of larger particle, which pile up at steep angles.

Question 9

What are sand beaches like?

Answer 9

Formed from smaller particles. Wide and flat.

Question 10

What are three distinctive features a beach might have?

Answer 10

Berms
Runnels
Cusps

Question 11

What are berms?

Answer 11

Ridges of sand and pebbles (about 1-2 meters high) found at high tide marks.

Question 12

What are runnels?

Answer 12

Grooves in the sand running parallel to the shore, formed by backwash draining to the sea.

Question 13

What are cusps?

Answer 13

Crescent-shaped indentations that form on beaches of mixed sand and shingle.

Question 14

Where do spits tend to form? Example?

Answer 14

Where the coast suddenly changes direction. E.g. across river mouths.

Question 15

Spits formation

Answer 15

Longshore drift continues to deposit material across mouth of river, leaving bank of sand and shingle sticking out into sea. Straight spit that grows out roughly parallel to coast is called a simple spit. Occasional changes to dominant wind and wave direction may lead to a spit having a curved end (recurved end). Over time, several recurved ends may be abandoned as waves return to original direction. Spit with multiple recurved ends from several periods of growth is a compound spit. Area behind spit sheltered form waves often develops mudflats and salt marshes.

Question 16

When are bars formed? Where can this occur?

Answer 16

When a spit joins two headlands together. Can occur across a bay or across a river mouth.

Question 17

What forms behind a bar?

Answer 17

A lagoon.

Question 18

What are offshore bars?

Answer 18

Bars that form off the coast (normally as sea level rises). May remain partially submerged by the sea.

Question 19

What is a tombolo? Example?

Answer 19

A bar that connects the shore to an island. E.g. St Ninian’s Isle in the SHetland Islands is joined to a larger island by a tombolo.

Question 20

What is a barrier beach?

Answer 20

A general term for any beach that shelters the coast, including barrier islands, spits and bars.

Question 21

What are barrier islands? Where do they tend to form?

Answer 21

Long, narrow islands of sand or gravel that run parallel to the shore and are detached from it. In areas where there’s a good supply of sediment, entail lope offshore, fairly powerful waves and small tidal range.

Question 22

Two theories how barrier islands formed:

Answer 22

After last ice age ended, when ice melt caused rapid sea level rise. Rising water flooded land behind beaches and transported sand offshore, where it was deposited in shallow water, forming islands.
Another theory - islands were originally bars, attached to the coasts, which were eroded in sections, causing breaches in the bar.

Question 23

What often forms behind barrier islands and why?

Answer 23

Lagoon or marsh because coast is sheltered from wave action.

Question 24

Example of where barrier islands are found

Answer 24

Many coastlines e.g. east coast of the USA - e.g. Horn Islnd Mississippi.

Question 25

Sand dune formation

Answer 25

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 e.g. marram grass. Vegetation stabilises sand and encourages more sand to accumulate, forming embryo dunes. Overtime, oldest dunes migrate inland as newer embryo dunes are formed. Mature dunes can reach heights of up to 10m.

Question 26

Where do mudflats and salt marshes form?

Answer 26

In sheltered, low energy environments, e.g. river estuaries or behind spits.

Question 27

How do salt marshes and mudflats develop?

Answer 27

As silt and mud are deposited by the river or the tide, mudflats develop. Mudflats colonised by vegetation that can survive the high salt levels and long periods of submergence by the tide. Plants trap more mud and silt, gradually they build upwards to create an area of salt marshes that remains exposed for longer and longer between tides.

Question 28

What forms channels on the surface of mudflats and salt marshes?

Answer 28

Erosion by tidal currents or streams form channels. They may be permanently flooded or dry at low tide.