Coasts EQ3 Flashcards
(33 cards)
What effect did the last ice age have on coastlines?
The sea level was at least 120m lower (more of the continents were exposed)
What are Milankovitch Cycles?
They are changes in Earth’s movement, which affect the amount of solar radiation causing an alternating pattern of ice ages & interglacial periods.
What is eccentricity?
The shape of the Earth’s orbit around the Sun every 100,000 years
What is obliquity?
The angle of the Earth’s axis in relation to the shape of its orbit, between 22.2-24.5 every 41,000 years
What is precession?
Earth wobbles on its axis, affecting the relationship of obliquity and precession every 23,000 years
What is evidence of natural long term climate change?
Ice cores in Antarctica measure atmospheric compositions of greenhouse gases from bubbles in ice cores.
What is post glacial isostatic adjustment?
The uplift of land following the removal of the weight of ice sheets
What is isostatic change?
A local rise or fall in land level
What is eustatic change?
a global rise or fall in water level caused by a change in the volume of water
What can cause an emergent coastline to be formed?
A eustatic fall in sea level during glacial periods
An isostatic rise of land by post glacial isostatic adjustment/coastal accretion
What can cause a submergent coastline to be formed?
-A eustatic rise in sea level after ice ages/thermal expansion
-An isostatic fall of land from post glacial adjustment/subsidence of land
What is an example of post glacial isostatic adjustment?
Scotland is rebounding, whilst Southern England is sinking
What landforms are created on emergent coastlines?
Raised beaches
Fossil Cliffs eg. Fife
What landforms are created on submergent coastlines?
Rias eg. Kingsbridge Estuary
Fjords eg. Norway
Barrier Islands
Dalmatian Coast (Croatia)
Why are sea level changes hard to predict?
There are uncertainties in science of relationships between climate feedback and greenhouse gases emissions + rate of ice melting
What influence does tectonic activity have on sea level changes?
-Can lift shoreline by several metres
-Can raise offshore islands and coral reefs out of the sea
-Can create rias
-IPCC believes it attributes up to 10% of sea level rise
Case Study: Kaikoura earthquake
-New Zealand, 2016
-Magnitude 7.8
-Seabed rose by 2.5m and up to 5.5m
-Formed raised beaches and exposed coral reefs
What influence does contemporary sea level have on low-lying land eg. Vanuatu?
-Increases the rate and risk of erosion
-Can wash away topsoil so crops can’t grow
-Encroachment of sea water on freshwater supplies
What human factor influenced a major storm at Hallsands, Devon in 1917?
Offshore dredging removed shingle from the sea and beach, leading to sediment starvation and increased rate of coastal recession
What are the 5 physical factors affecting the rate of coastal recession?
-Fetch (long + large leads to destructive waves)
-Geology + Lithology of Rocks
-Cliffs with structural weaknesses eg. dips/faults
-Cliffs vulnerable to mass movement+weathering
-Strong longshore drift
What are the impacts of Aswan High Dam, Egypt on coastal recession?
River discharge fell from 35b to 10b
Sediment volume fell from 130m tonnes to 15m tonnes
Sediment is trapped by reservoir + dam, leading to sediment starvation and erosion rate increasing
Why are there spatial variations in the rates of erosion on Holderness Coast?
-Coastal defences in Hornsea, Mappleton
-Sediment starvation in the South due to groynes
-Variations in cliff height + susceptibility to erosion
-Susceptibility to mass movement
-Past debris and mass movement can protect cliffs
Why are there temporal differences in the variations of erosion rates on Holderness Coast?
-Winter storms cause more erosion
-Differences in fetch
-Storms are rare in summer months, so erosion rates in autumn are lower
What are the social impacts of coastal recession on Skipsea?
-Loss of homes
-Residents need to be displaced
-Health impacts eg. stress/anxiety
