Coasts EQ3 - Coastal erosion and sea level change Flashcards
What is eustatic change?
A rise or fall in water level caused by a change in the volume of water - GLOBAL change
What is isostatic change?
A local rise or fall in land level
How can eustatic change cause rises and falls in sea level?
During glacial periods, ice sheets form and ‘lock up’ water from the sea, causing a fall in sea level (MARINE REGRESSION)
At the end of glacial periods, melting ice sheets return water to the sea. Global temperature rise also cause thermal expansion, causing sea level rise (MARINE TRANSGRESSION)
How can isostatic changes cause rises and falls in land level?
Post glacial-adjustment causes isostatic rebound due to the weight of ice sheets melting off of crust - lifting the land surface out of the sea (MARINE REGRESSION)
Land can sink at coasts due to accretion of sediment and a seesaw effect causes subsidence (MARINE TRANSGRESSION)
What is an emergent coastline?
Parts of the littoral zone where a fall in sea level has exposed land once part of the sea bed
What features are found on an emergent coastline?
Raised beach
Fossil cliff
What is a raised beach?
A relict beach now above high tide level, usually vegetated by plant succession
What is a fossil cliff?
A steep slope found at the back of the beach exhibiting evidence of formation through marine erosion, now above high tide level
What is a submergent coastline?
Sections of the littoral zone where sea level rise has inundated areas that were previously part of terrestial land
What features are found on a submergent coastline?
Rias, fjords and Dalmatian coastlines
What is a ria?
A drowned river valley, flooded by the sea and wider than expected (estuarine coastline)
What is a fjord?
Drowned glacial valley flooded by the sea
What is a Dalmatian coastline?
Long narrow islands running parallel to the coastline, separated from the coast by narrow sea channels called sounds
What are some of the key facts on past and future sea level rise?
Past - in the last 18,000 years sea levels have risen by 140m
Future - IPPC predicts sea level rise of 50cm by 2100, every degree rise in temperature causes a 0.8mm sea level rise
Why is sea level rise difficult to predict?
- uncertainties in science of relationship between climate change and melting ice
- thermal expansion depends on global temperature rise and is hard to predict
- uncertainty on when and how much ice sheets will melt
- uncertainty on GHG emissions and climatic warming