Enquiry Question 3: How do erosion and sea level change alter physical characteristics of coastlines? Flashcards
Eustatic change
Global sea level change associated with ice-age activity (e.g. formation of ice, melting of ice sheets).
Isostatic change
Local changes in land height relative to sea level. This can be attributed to tectonics activity, subsidence and and post-glacial rebound.
Tectonic activity
Movement of tectonic plates (e.g. thrust fault) can lift or lower land in relation to sea level.
Post-glacial adjustment
After the melting of ice sheets, the land slowly rebounds over thousands of years. This process can slowly lift land out of the sea.
Subsidence
The sinking of the land - causes coastal land to be submerged. This can be caused by the over-abstraction of groundwater supplies, mining and erosion (e.g. erosion of deposited sediment on deltas).
Accretion
Deposition of coastal sediment leads to ‘crustal sag’ under the weight of the sediment (slow process).
Emergent coastline
Sea level drops relative to land, exposing former sea bed.
Submergent coastline
Land is flooded and the coastline is ‘drowned’..
Coastal recession
The erosion of coastlines at a rapid rate, resulting in loss of land, homes and businesses.
Dredging
Scooping/sucking sediment from the sea/river bed. This deepens the sea/river bed to allow larger boats to pass.
Coastal Management
Using hard engineering/soft engineering to modify, or adapt to, coastal processes.
Vegetation removal
Deforestation of plants/trees, such as mangrove forests, removes a natural coastal defence system. This can increase the likelihood, and severity, of coastal erosion and flooding.
Storm surge
The rising of the sea as a result of wind and atmospheric pressure changes associated with a storm. This results in higher than normal tides, and tsunami-like flooding.
Depressions/cyclones
Areas of low air pressure are associated with strong winds, high rainfall and storm surges.
Flooding
Cover or submerge an area with water
What causes a EUSTATIC fall in sea level?
Glacial periods (every 90,000 years) cause the earth’s climate to cool. More precipitation falls as snow and is stored as snow and ice (glaciers and ice sheets). Less water flows through the water cycle, so sea levels fall (reduced volume of sea water).
What causes a EUSTATIC rise in sea level?
Interglacial periods cause a warming of the climate which melts snow and glaciers and more precipitation falls as rain. Rain and snow/ice melt runs off in to the oceans, causing a rise in sea level (increased volume of sea water). Thermal expansion also contributes to rising sea levels.
Thermal Expansion
As oceans become warmer due to global warming, sea water expands slightly, contributing to rising sea levels.
What causes ISOSTATIC rise in sea level?
Post-glacial adjustment, accretion and tectonics.
What causes ISOSTATIC fall in sea level ?
Post-glacial adjustment, subsidence and tectonics.
What is Isostatic Subsidence?
During ice ages the weight of the ice sheets makes the land sink.
What is Isostatic Recovery/Rebound?
As the ice begins to melt at the end of a glacial period, reduced weight of the ice sheets causes the land to readjust and rise.
