1.3 How do coastal landscapes evolve over time as climate changes? Flashcards
(15 cards)
What are Eustatic Changes and what are they influenced by?
Changes in the volume of water in the global ocean store are known as
eustatic changes. These changes are influenced by variations in mean
global temperatures, affecting both the amount of water in the ocean store and density.
Physical factors that can affect changes in global
temperature and the volume of water in the oceans
- variations in the Earth’s orbit around the Sun, typically every 400,000
years - variations in the amount of energy produced by the Sun, with a solar
maximum every eleven years or so - changes in the composition of the atmosphere due to major volcanic
eruptions which reduce incident solar radiation - variations in the tilt of the Earth’s axis, occurring every 41,000 years
What are glacial and Interglacial periods?
Glacial - A colder phase where ice sheets expand and sea levels fall due to water being stored on land as ice.
Interglacial - A warmer period between glacial periods, characterised by rising global temperatures and sea levels.
Recall the key climate periods relevant to past sea level fall during a previous time period (130000 - 108000 years ago)
Tyrrhenian interglacial (~130,000 years ago):
Temperatures ~3°C warmer than today
Sea level ~20m higher than today
Riss glacial (~108,000 years ago minimum):
Temperatures ~7°C cooler than today
Sea level fell over 100m → ~83m below current level
What key climate period occurred between the Riss glacial and the Holocene, and what were its impacts on sea level?
Würm glacial period (last glacial period, ~115,000 to ~11,700 years ago)
Includes the Last Glacial Maximum (~18,000 years ago)
Temperatures much lower than today
Sea level dropped by up to 120m below present levels due to ice sheet expansion
What is the current climate period and how has it affected sea levels?
Holocene interglacial (began ~11,700 years ago)
Marked by a warming climate after the Würm glacial period
Sea levels have risen by ~120m due to melting ice and thermal expansion
Human-induced climate change is now accelerating sea level rise
Explain the influence of sea level rise and geomorphic processes in the formation of rias.
Formation Process: A ria is created when a river valley is submerged by rising sea levels, resulting in the flooding of the valley’s floor and the coastline.
Sea Level Rise Influence: During periods of glacial melting and global warming, sea levels rise, flooding the valley and creating a drowned river valley.
Geomorphic Processes:
River Erosion: The river carves out the valley through abrasion and hydraulic action, creating a V-shaped valley.
Submergence: As sea levels rise, the valley floor and lower areas are flooded, forming the ria.
Key Features:
Long, narrow bays with gentle slopes along the sides of the valley.
Irregular shape due to the meandering path of the river.
Example: Ria de Arosa, Spain, is a classic example where sea level rise has flooded an old river valley, creating a ria.
Explain the influence of sea level rise and geomorphic processes in the formation of Fjords
Formation Process: A fjord forms when a glacial valley, previously carved by glacial erosion, is submerged by rising sea levels.
Sea Level Rise Influence: During the end of the last Ice Age, glacial retreat and melting ice caused sea levels to rise, flooding the valley, creating a deep and long fjord.
Geomorphic Processes:
Glacial Erosion: Over thousands of years, glaciers carve out the valley using processes like plucking and abrasion, forming a U-shaped valley.
Submergence: As the ice melts, rising sea levels flood the U-shaped valley, forming a fjord.
Key Features:
Steep cliffs on either side of the fjord, often with hanging valleys and waterfalls.
Deep waters, much deeper than the surrounding coastal areas.
Example: Sognefjord, Norway, is a well-known fjord where a glacial valley has been flooded by sea level rise.
Explain the influence of sea level rise and geomorphic processes in the formation of Shingle Beaches
Formation Process: Shingle beaches form as waves and longshore drift transport and deposit coarse material like pebbles and gravel along the coastline.
Sea Level Rise Influence: Rising sea levels can lead to increased wave energy, contributing to the accumulation of shingle on the beach.
Geomorphic Processes:
Wave Action: The force of waves moving in and out transports material along the shore.
Longshore Drift: This process moves shingle along the coast, and where the energy of the waves drops, shingle accumulates, forming the beach.
Key Features:
Coarse material such as pebbles and gravel with a steep profile.
Beaches often have a long, narrow shape and vary in size depending on wave strength and sediment availability.
Example: Dungeness, UK, is a famous shingle beach where the combination of longshore drift and high-energy waves has formed a large and distinctive beach.
Explain how rias are modified by present climate and sea level changes
Present Modifications:
Sea level rise due to melting polar ice and thermal expansion is submerging more land, enlarging rias.
Increased storm intensity (due to climate change) leads to higher wave energy, contributing to erosion along the valley sides.
Flooding of previously exposed land leads to widening and deepening of rias.
Explain how rias are modified by future climate and sea level changes
Future Modifications:
Continued sea level rise will lead to further submergence of low-lying areas and expansion of rias.
More frequent and intense storms will lead to accelerated erosion and deeper rias.
Loss of land due to further flooding and erosion could result in rias becoming even more expansive or entirely submerged.
Explain how fjords are modified by present climate and sea level changes
Present Modifications:
As glaciers melt due to global warming, fjords are deepening and widening.
Increased wave energy and storm surges (due to climate change) are contributing to erosion of fjord sides.
Sea level rise allows more water to enter fjords, increasing their depth and potentially flooding new areas.
Explain how Fjords are modified by future climate and sea level changes
Future Modifications:
Continued glacial retreat and temperature rise will cause further deepening of fjords.
Sea level rise will continue to flood fjords, possibly leading to the complete submergence of previously exposed parts.
Increased erosion from higher wave energy and more frequent storms could reshape the fjord landscape.
Explain how Shingle Beaches are modified by present climate and sea level changes
Present Modifications:
Sea level rise increases wave energy, leading to erosion of shingle beaches and altering the beach profile.
More frequent and intense storms (due to climate change) cause shingle movement, shifting the beach and changing its shape.
Increased storm frequency erodes beaches and reduces the volume of shingle, contributing to loss of the beach in some areas.
Explain how Shingle Beaches are modified by future climate and sea level changes
Future Modifications:
Continued sea level rise will likely result in further erosion of shingle beaches, particularly if sediment supply cannot keep up with rising water levels.
The intensification of storms will continue to erode and displace shingle, possibly leading to the disappearance of some beaches.
Coastal defenses, like sea walls, may alter natural processes, preventing shingle movement but also affecting the long-term evolution of the beach.
