Sea level change

Question 1

What is Geological time?

Answer 1

Time is measured over millions of years.

Question 2

What causes natural climate changes?

Answer 2

Caused by orbital change, if the Earth is closer or further away from the sun then the Earth will change temperature

Caused by the eruption of volcanoes releasing chemicals like sulfur into the air.

Question 3

How has sea level changed over time?

Answer 3

Sea level’s rose dramatically 140,000 years ago but began fluctuating up and down but slowing getting lower and lower but in the last 10,000 years sea levels rose dramatically and are at their highest levels since being very low 20,000 years ago.

Question 4

What is the name of the current climatic period?

Answer 4

The Holocene

Question 5

What is Eustatic change?

Answer 5

Global change in sea levels

Question 6

What is isostatic change?

Answer 6

Local change in land levels

Question 7

What is tectonic activity?

Answer 7

Movement of the plates of the Earth.

Question 8

What factors would cause sea levels to fall?

Answer 8

• An ice age
• Tectonic activity opening up trenches for water to sink into

Question 9

What factors would lead to a sea level rise?

Answer 9

• Ice melting
• Global warming leading to thermal expansion, water size increases by 9%

Question 10

What factors would lead to a fall in land level?

Answer 10

Tectonic processes (submergence)
Crustal sag - Weight of glaciers clausing land to sink.

Question 11

What factors would lead to a rise in land level?

Answer 11

Tectonic processes (folding)
Post glacial uplift/rebound 2

Question 12

What is Isostatic change in sea level and what causes it?

Answer 12

Land can ‘sink’ at the coast due to the deposition of sediment (accretion), especially where the weight of sediment leads to very slow crustal sag and delta subsidence

Question 13

What is an isostatic fall in sea level and what causes it?

Answer 13

During the build up of land-based ice sheets, the colossal weight of the ice causes the Earth’s crust to sag. When the ice sheets melt the land surface slowly rebounds upwards over thousands of years.. This post glacial uplift slowly lifts the land surface out of the sea.

Question 14

What is a submergent coastline?

Answer 14

When the sea level rises (Due to high rates of melting ice, for instance at the end of an ice age) or the land level lowers (Due to crustal sag or tectonic activity), previously visible coastlines disappear under the water
E.G Rias, Fjords

Question 15

What is an Emergent coastline?

Answer 15

When the sea level lowers (Due to a high rate of ice forming, for instance during an ice age, thermal expansion or global warming) or a rise in land level (Due to post glacial rebound or tectonic activity), previously submerged coastlines reappear above the water.
E.G Raised beaches.

Question 16

What are the stages of the formation of a raised beach

Answer 16

1. Before the last ice age the sea eroded
   the cliffs creating landforms such as
   caves, beaches, and stacks.
2. The climate begins to get colder,
   marking the onset of a new glacial
   period, increasing the amount of
   precipitation falling as snow.
   Eventually this snow turns into
   glacial ice which acts as a store
   for water and slows down the
   hydrological cycle.
3. The weight of glacier causes the
   land surface to sink. Such a
   movement is said to be isostatic.

4.The climate gets warmer. Eventually
ice masses on the land begins to melt.
This starts to replenish the main store
and sea levels begin to rise

5.As the ice is removed from some land areas
they begin to move back up to their previous
levels (isostatic readjustment). If the
isostatic movement is faster than the
eustatic, emergent features are produced
such as raised beaches.

Question 17

What is a storm surge and how are they formed?

Answer 17

Abnormal rise of water generated by a storm over and above the predicted tide

Caused by strong winds in a hurricane or tropical storm, low pressure has minimal contribution.

Question 18

What are the factors that influence storm surges?

Answer 18

• Size of tropical storm, the winds of the storm push on a larger area of the ocean’
• Shape of the coastline, A concave coastline curving in wards and the storm surge will be less destructive and convex is shaped outwards and storm surge will be less
• Tidal range of coastline
• Width and slope of ocean bottom, Higher storm surges more effective with gentle slope and less effective with a narrow beach
• Angle of approach, storms approaching at a perpendicular angle will be more destructive to the coast.
• Local factors, Little coastline protection etc
• Storm intensity and speed, Stronger and faster winds produce a higher storm surge

Question 19

How are storm surges likely to increase?

Answer 19

• Projected to increase by at least 20%
• This is because of the rising temperature of the Atlantic ocean

Question 20

What is the most likely sea level rise by 2100?

Answer 20

45cm