EQ3 Risk Affecting Coasts Flashcards
What is the Nile delta
Is the final stretch of the river mile before it empties into the Mediterranean Sea (22,000 km squared) one of the largest cities sits on it population of 5.4 million
How vulnerable is the delta
In 2015 a study shows 32.5% of the Nile delta coast is highly vulnerable
If sea levels rise by 1m by the end of the century 2 million hectares of fertile land will be lost
3 Marine processes causing rapid coastal recession
Wave type – destructive, high energy, prevailing winds, fetch, winter storms
Tides– high tides may mean waves reach the backshore
Submerging coastline – exposes cliffs to more erosion
2 geology factors causing rapid coastal recession
Geology – less resistant to erosion, weak unconsolidated rock
Lithology-jointed rock, rock with bedding layers
2 subaeriel processes causing rapid coastal erosion
Weathering-Salt crystallisation
Mass movement- for eg permeable strata overlying impermeable strata
How does wave type influence rates of erosion
Destructive waves have the most energy and a strong backwash, so are more effective at eroding (e.g. through hydraulic action and abrasion) as they hit the cliff face with greater force then constructive waves
How does wave size influence rates of erosion
The size of the wave affects erosion rates. Larger waves give more energy than smaller waves, so they exert more power erode the coast more quickly.
How does lithology influence rates of erosion
Soluble rocks as well as softer, less resistant rock is more vulnerable to erosion. Rocks that have a large number of fractures erode more easily through hydraulic action as the waves penetrate into the rock
2 Human actions causing rapid coastal recession
Dam building-on a river it interferes with the movement of sediment through the river and will also be less sediment for LSD to move within the cell therefore increase rates of erosion further along the coastline
Dredging- removing sediment from the cell permanently increases recession rates as it starves the beach of new sediment
Located place Holderness
Why is erosion such a problem
Because it consists of boulder clay and BC has little resistance to erosion producing shallow, sloping cliffs
Exposed to wind and waves across a 500-800km fetch
Low pressure weather systems and winter storms passing over the North sea are often Intense producing strong winds, waves and high tides
What does anthropogenic mean
The influence of humans
Long term sea level change refers to
A result from many factors such as eustatic (ice forming and melting) and isostatic (subsidence, accretion and tectonics)
What is the greenhouse effect
The retention of heat in the atmosphere caused by the build up of greenhouse gases, radiating heat back to earth.
What is solar radiation
LW SW
Long wave is-Heat energy (infrared) emitted by the Earth’s surface after absorbing solar energy; part of the Earth’s energy loss to space.
Short wave-Energy from the Sun, including visible light and UV, that reaches and heats the Earth’s surface
What is enhanced greenhouse effect
Increased concentration of greenhouse gases (human induced) means that they are more effective at preventing heat being lost into space
More long wave radiation is reflected back to earth
What is contemporary sea level rise
Contemporary sea level rise refers to the ongoing increase in global sea levels due to climate change.
What are the drivers of contemporary SLR
is primarily driven by:
1. Thermal Expansion – As global temperatures rise, seawater expands, leading to higher sea levels.
2. Glacial and Ice Sheet Melt – Melting glaciers and ice sheets in Greenland and Antarctica contribute vast amounts of water to the oceans.
3. Land Water Storage Changes – Human activities, such as groundwater extraction and dam construction, also impact sea levels
Tectonic activity and SLR
Large earthquakes and volcanic eruptions can create chant in the shape of land
Movements in entire plate positions can change the capacity of the ocean basin, so can rise or lower sea level
How seal level change from GW or tectonic change creates risks
Low lying islands such as the Maldives will disappear this is expected to submerge by 2100 along with coastal ecosystems
Stormier seas are also a general climate change prediction with stronger stems such as mid latitude depression creating larger more destructive waves this will accelerate coastal erosion
Summary of causes of contemporary SLR %
Thermal expansion -40%
Melting ice- Greenland ice sheet 25%, Antarctica ice sheets 10% mountain glaciers and ice caps 15%
Mountain glaciers and ice caps 15%
tectonic activity- 10%
what is marine regression
the effect on a coastline is the former seabed is exposed as the sea level drop producing an emergent coast
what is marine transgression
blow areas of land flood so the coastline is ‘drowned’ producing a submergent coast
how is eustatic SLR caused
by a change in the volume of water in the sea, or by a change in the shape of the ocean basins. the causes and effects are global and happen relatively quickly
what is a eustatic fall in sea level
global decrease in sea level caused by a reduction in the volume of water in the oceans or a change in the ocean basin capacity.
