Coasts part 5
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What is eustatic sea level change?
A rise or fall in sea level due to an increase or decrease in the volume of sea water
What is isostatic sea level change?
- The movement of the land in response to the release of the weight of ice on the land.
- Scotland going up, south england going down
What is the sequence of sea level change?
- 1. climate cools so precipitation falls as snow. global sea levels fall
- 2. weight of ice sheets causes land to sink
- 3. climate warms, ice melts (eustatic rise) and forms of submergence appear
- 4. land springs back (isostatic change)
If all of the ice caps melted how much would sea levels rise by?
How much is southern England sinking by each year?
Name the landforms of submergence
- Drowned islands
Do rias form on discordant or concordant coastlines?
What is the difference between a ria and a fjord?
- Rias are drowned river valleys whereas fjords are drowned glacial valleys.
- Fjords are deeper inland and shallower towards the sea
Do drowned islands form on discordant or concordant coastlines?
Describe and explain the formation of a ria
- Rias are long, simple inlets found where rivers follow the planes of weaknesses in rocks (which are not well aligned and tributaries may flow) when the sea level was lower
- Formed when sea levels rise and rivers are cut down to a base level (as much as 100m below sea level) which then flooded
Describe and explain the formation of a fjord
- Fjords are long, narrow, steep sided inlets with hanging valleys (often marked by waterfalls).
- Formed by glaciers that eroded deep troughs below the present sea level which then flooded in eustatic sea level rise.
Where can the largest fjords be found?
In line with existing lines of geological weakness
Describe and explain the formation of drowned islands
- Drowned islands are hills that once ran parallel to the coast that have been flooded. The islands are the summits of former coastal mountain range
- Caused by eustatic and isostatic changes which gradually take place due to tectonic plates shifting
Describe and explain the formation of raised beaches
- A line of degraded cliff fronted by a former wave cut platform, often with beach deposits resting on it
- Result of sea levels falling and beach being raised out of reach of wave activity.
Describe and explain the formation of abandoned/relict cliffs
- Cliffs that were once on the coast that have now risen above the level of the land
- Caused by a fall in sea levels meaning that waves cannot attack cliffs leaving them isolated
Describe and explain the formation of slope-over cliffs
- Cliff slopes down towards the coast
- Cliff is abandoned by sea and degraded by solufluction and frost. As sea levels rise the slope erodes, the rate of which is dependant on how sheltered or exposed it is. Very exposed cliffs erode the entire pre-glacial slope whereas sheltered cliffs will not.
- The lower steep face is a result of present day erosion
Example of drowned islands
Dalmatian coast, Croatia
How many homes in the UK are at direct risk of flooding?
If all of the ice caps melted, which countries would be most at risk and why?
Low-lying countries such as Netherlands and Vietnam. Lots of people live here and land would be flooded
If all the ice caps in the world melted, which country and areas would be completely lost?
Which continent would suffer the least loss if all the ice caps melted?
Africa (they are more likely to be affected by global warming's heat)
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