Sea level change

Question 1

How do erosion and sea level change alter the physical characteristics of coastlines and increase risk?

Answer 1

• Short and long term sea level changes influence the physical geography of coastlines and increase risks for people
• rapid coastal recession happens because of both physical and human influences
• coastal flooding is a significant risk on some coastlines, worsened by global warming, uncertain of extent

Question 2

Isostatic change

Answer 2

A local rise or fall in land level

Question 3

Eustatic change

Answer 3

Involves a rise or fall of water level caused by a change in volume of water. Global change, affects worlds connected seas and oceans.

Question 4

Why is sea level change complex?

Answer 4

• both isostatic and eustatic change can happen at the same time

Question 5

Why do sea levels change from day to day?

Answer 5

• high and low tides
• low atmospheric pressure causes slight increase in sea level
• winds push water towards coasts, wave height varies.

Question 6

Emergent coast

Answer 6

Where a former seabed is exposed as sea level drops

Question 7

How do isostatic and eustatic changes cause an emergent coast?

Answer 7

• Eustatic sea level fall caused by glacial periods and ice sheets on land lock water evaporated from the sea into ice at high altitudes.
• isostatic fall cause by a build up of land based ice sheets melting, causes land surface to rebound upwards over time

Question 8

Submergent coast

Answer 8

Where the coastline is drowned.

Question 9

How do isostatic and eustatic changes cause a submergent coast?

Answer 9

• Eustatic rise in sea level caused by melting ice sheets returning water to sea and causes a global sea level rise.
• As global temperature increases, causes the volume of ocean water to increase (thermal expansion), leads to sea level rise.
• Isostatic sea level rise caused when land sinks due to deposition of sediment. Weight of sediment deposition causes crustal sag.

Question 10

Post glacial adjustment

Answer 10

refers to the uplift experienced by land when the weight of ice sheets is removed.

Question 11

Emergent coastline example

Answer 11

West coast of North America

Question 12

Submerging coast example

Answer 12

East coast USA

Question 13

Features of an emergent coastline

Answer 13

Raised beaches reflecting previous sea levels

Question 14

Submergent coasts landforms

Answer 14

• Ria
• Fjords
• Barrier island

Question 15

Ria

Answer 15

Drowned rivier valleys in unglaciated areas, caused by sea level rise and flooding up the river valley, making it much wider than would be expected based on the river flowing into it.

Question 16

Where can fjords be found?

Answer 16

Norway and Canada

Question 17

How do fjords differ from rias?

Answer 17

• drowned valley is a u shaped glacial valley
• fjord is often deeper than adjacent sea
• at seaward end of the fjord, there is a submerged lip representing the former extent of the glacier that filled the valley.

Question 18

Barrier Island

Answer 18

offshore sediment bars, usually sand dune covered, but not attached to the coast.

Question 19

Where can barrier islands be found?

Answer 19

The east coast of the USA

Question 20

How do barrier islands form?

Answer 20

• once coastal sand dunes attached to the shore

- sea level rise flooded land behind dunes, formed a lagoon, dunes not eroded so became islands.

Question 21

Dalamtian coast and sea level rise

Answer 21

Consists of anticlines and synclines .

Post glacial sea level rise submerged the area, creating bays in areas that were once low-lying valleys.

Question 22

Accretion

Answer 22

When sediment is added to a landform by deposition. Can build up to form new land, balanced by subsidence caused by the weight of the newly deposited sediment

Question 23

How has sea level changed, or is changing?

Answer 23

• stable early 1800s
• started rising slowly, but accelerated after 1940, and is accelerating even faster now.
• expected to increase by 100cm by 2100

Question 24

How has measuring sea level changed over time?

Answer 24

It has become more accurate as tide gauges and satellite measurements have became more accurate

Question 25

Why is sea level difficult to predict?

Answer 25

• Thermal expansion depends on how high global temperatures rise
• melting of mountain glaciers will increase sea level rise
• melting ice sheets will increase sea level.
• can change locally due to tectonic forces, for example earthquakes can force land up or down

Question 26

Thermal expansion

Answer 26

The main driver of sea level rise, occurs because the volume of ocean water increases as global temperatures rise