Coasts EQ3

Question 1

What are the two types of sea level change?

Answer 1

Isostatic

Eustatic

Question 2

What is eustatic change and what scale does the change occur on?

Answer 2

Change in sea level as a result of the changing level in the volume of water in the oceans

Global

Question 3

What is isostatic change and what scale does the change occur on?

Answer 3

Change in sea level as a result of the changing level of the land.

Local/ regional

Question 4

What were the sea levels 1800 years ago compared to now?

How quickly are sea levels currently rising?

How much is the sea level expected to rise by 2100?

Answer 4

110m lower

3.2mm per year

4-6m

Question 5

What are the 3 causes of isostatic change?

What are the 3 causes of eustatic change?

Answer 5

• Tectonic activity
• Glaciation
• Post-glacial readjustment
• Thermal expansion
• Changes in ice sheet extent
• Tectonic activity

Question 6

Explain the causes of isostatic changes.

Answer 6

• Tectonic activity: Folding of sedimentary rock by compressive forces at a destructive plate margin produces an isostatic fall in sea level for anticlines and a fall for synclines. Lava or ash from volcanic activity produces an isostatic fall. e.g. Hawaiian hot spot island chain or Caribbean island arc. During the 2004 Boxing Day Tsunami in the Indian Ocean extension of the crustal plate caused an isostatic fall in the land on the island of Sumatra by 20 cm in the Banda Aceh region.
• Glaciation: As water is stored on the land in glaciers, the weight of the land increases and the land sinks slightly, causing the sea level to rise slightly. This is referred to as compression.
• Post-glacial readjustment: During glacial periods, the weight of the ice depresses the crust in areas below the ice sheets. The solid lithosphere is forced down into the plastic asthenosphere. The rigid nature of the solid crust means that when sections of the crust are depressed by ice and forced down, adjacent areas are uplifted in a see-saw effect. The melting of ice causes the previously ice-covered crust to slowly rebound upwards whilst adjacent areas subside.

Question 7

Explain the causes of eustatic changes.

Answer 7

• Thermal expansion: Rising water temperature leads to the thermal expansion of water, increasing its volume even further. This leads to marine transgression - rising sea levels flood lowland areas.
• Changes in ice sheet extent: Melting of sea ice has no effect on global sea levels as the floating ice mass already displaces its volume.
• Tectonic activity: Rising magma at a constructive plate margin/hot spots lifts the overlying crust, reducing the capacity of the ocean and producing eustatic sea level rise. Uplift of crustal plate reduced Indian Ocean capacity causing a 0.1 mm eustatic rise in global sea levels.

Question 8

What is happening in Kiribati?

Why are the sea levels rising?

What is next for Kiribati?

Answer 8

2014 president of Kiribati finalised the purchase of 2km2 of one of the Fijan islands. 200km from Kiribati. Kiribati consists of 33 widely spaced islands- low lying. Rising by 1.2cm a year.

Due to thermal expansion, ice sheets are melting.

Land purchased by Kiribati will be used for the future for agriculture and fish farming projects to guarantee the nations food security. They’ll be environmental refugees.

Question 9

What are submergent coastlines and examples?

Answer 9

A rise in sea level floods the land. e.g Ria, Fjard, Fjord, Dalmatian coast.

Question 10

What are emergent coastlines and examples?

Answer 10

A fall in sea level exposes land previously covered by the sea. e.g Raised beaches, Fossil/ relic cliffs.

Question 11

What are raised beaches and an example?

Answer 11

A flat surface covered by sand or rounded pebbles/boulders above sea level. Usually vegetated by plant succession (though further succession prevented due to grazing)

Raised beaches and marine terraces are beaches or wave-cut platforms raised above the shoreline by a relative fall in the sea level.

e.g. Isle of Arran

Question 12

What are fossil cliffs and an example?

Answer 12

A steep slope found at the back of a raised beach exhibiting evidence of formation through marine erosion but now above high tide level. They may contain wave-cut notches, caves and arches providing evidence of formation by marine erosion.

Isle of Arran

Question 13

What is a ria and an example?

Answer 13

A drowned river valley with winding inlets - a section of river valley flooded by the sea, making it much wider than would be expected based on the river flowing into it. Rivers eroded steep-sided V-shaped valleys into the frozen landscape giving the ria a V-shaped cross-section when the valley flooded. Rias are a type of estuarine coastline.

South west England

Question 14

What is a fjord and an example?

Answer 14

Are drowned glacial valleys - a section of a glacially eroded valley flooded by the sea. They are common in glaciated areas that were covered during the last glacial period.

Norway, New Zealand, Chile

Question 15

What is a fjard and an example?

Answer 15

Flooded inlet with a low rocky banks on either side formed by post glacial drowning of glaciated lowland terrain. Islands called series.

Question 16

What is a Dalmatian coast and an example?

Answer 16

Long, narrow islands run parallel to the coastline and are separated from the coast by narrow sea channels called sounds.

A dalmatian coastline is formed where the geology creates valleys parallel to the coast so that when the sea level rises, a series of elongated islands remain offshore.

e.g Croatia

Question 17

What human factors are found on the 240km coast of the Nile Delta?

How much is the coastline retreating by?

What was built there?

Answer 17

• Fisheries - Settlements
• Toursim - Transport
• Holiday beach resorts. - Agriculture

3.3%

Aswam Dam was built in 1963 which increased coastal recession.

Question 18

What’s the location description of Holderness?

Answer 18

The Holderness coast is located on the east coast of England and is part of the East Riding of Yorkshire; a lowland agricultural region of England that lies between the chalk hills of the Wolds and the North Sea.

Question 19

What is happening at Holderness?

Answer 19

Europe’s fastest eroding coastlines. The average annual rate of erosion is around 2 metres per year. The main reason for this is that the bedrock is made up of till (soft clay). This material was deposited by glaciers around 12,000 years ago.

Physical causes:
- The bedrock is made up of till. This material was deposited by glaciers around 12,000 years ago and is unconsolidated.
- Holderness Coast is a lowland coastal plain deposited by glaciers. The boulder clay is experiencing more rapid rates of erosion compared to the chalk.

Human causes:
- Decision makers in Mappleton have protected the base of the cliff with rock armour and placed two large rock armour to act as groynes to build up the size of the beach.
- Humans can influence the rates of erosion through the choice of coastal management they deploy. A number of methods are known to increase rates of erosion. Sea walls, provide solid protection to coastal towns and promenades. However, their curved solid design reflects wave energy rather than absorbing it and so the wave energy is returned to the beach. As a result, beaches become eroded and the sea wall without beach replenishment will become exposed and undermined.

Question 20

What are the factors affecting coastal recession?

Answer 20

• Wind direction
• Tides
• Weather systems
• Seasons
• Storm activity
• Vegetation

Question 21

How does wind direction affect coastal recession?

Answer 21

Rates of recession are higher when the wind is blowing onshore. Offshore winds produce calm conditions. The dominant wind is the direction of the strongest wind. When the wind blows from the prevailing wind, strong winds produce destructive waves, and rapid recession.

Question 22

How do tides affect coastal recession?

Answer 22

Spring tides: At a new moon and full moon have extreme tides. Neap tides: At half moon and aren’t as strong. Occur 2x a year.

Question 23

How do weather systems affect coastal recession?

Answer 23

Anti Cyclones form high-pressure form gentle waves. Depressions are areas of low pressure that form rapid rates of coastal recession.

Question 24

How do seasons affect coastal erosion?

Answer 24

Winter waves create more destructive waves than summer waves. In winter, the difference between the temperature at the equator.

Question 25

How does storm activity affect coastal recession?

Answer 25

Storm events are deep depressions. They produce large, high-energy waves and fast rates of recession. Global warming is predicted to increase the intensity of global atmospheric circulation.

Question 26

What are the global and local factors that increase flood risk?

Answer 26

Local:
- Isostatic subsidence
- Removal of mangroves
- Low-lying coastline

Global:
- Sea level rise
- Tropical cyclones and storms
- Global warming

Question 27

Why is vegetation at the coast important?

Answer 27

• Reduces height of waves by 40% within the first 100m of coast.
• Traps sediment.
• Reduces storm surge levels by 0.5m for every 1km.