Emergent and submergent features Flashcards
What is eustatic change?
A global change in sea level resulting
from an actual fall or rise in the level
of the sea itself. Occurs quickly
eg. formation of ice sheets, melting of ice caps/glaciers, sea level rise
What is isostatic change?
Local changes in sea level resulting
from the land rising or falling relative
to the sea. Occurs over a long period of time
eg. weight of ice sheet makes land sink (isostatic subsidence), ice melts causing land to rise (isostatic recovery)
What are the impacts of sea level change?
- increased coastal flooding and erosion
- impact on underground water resources which is abstracted for domestic and irrigation purposes
- major rail and road links at risk
- loss of villages/homes
How is the volume of the ocean increasing?
- As the Earth’s climate warms, both naturally and due to current warming
related greenhouse gas emissions and a human-induced enhances greenhouse effect, water currently stored on the surface as ice is released
into the oceans as it melts. - Thermal expansion of the oceans
What are rias and how do they form?
Submergent features which form when valleys are flooded, leading to the drowning of lower portions of river valleys. The old river course is flooded and many rivers and tributaries are drowned. They can form natural harbours and are common in south west England eg. Knightsbridge estuary. Form due to rising sea levels due to climate change
What are fjords and how do they form?
Submergent features formed when glacial troughs are flooded. They are straight, narrow and deep with very steep sides. They have a typical U shaped cross profile and tend to be shallowest at the mouth due to glacial deposits, which marks where the glacier left the valley. They are a common landform along the coast of Norway eg. Sogne Fjord
What are raised beaches and relic cliffs and how do they form?
Emergent features - beaches and cliffs which are elevated areas of sloping ground sitting above the present tide line. In the past this area was at sea level. As the land rose as a result of isostatic recovery, former wave-cut beaches and their beaches were raised above present sea levels. eg. found on the West coast of Scotland and Isle of Arran (which experienced the greatest weight of ice during the ice age)
What are dalmatian coasts and how do they form?
Submergent features that are long, narrow islands parallel to the coastline. They form in a landscape of ridges and valleys running parallel to the coastline. When sea levels rise, the valleys flood although the tops of the ridges remain exposed, forming a series of offshore islands parallel to the coast eg. Dalmatian coast in Croatia.
What are marine platforms and how do they form?
Emergent features
How has the rate of sea level rise changed recently?
In recent millennia sea levels have risen slowly, about 2mm/year, but the rate recently has increased to 4-5mm/year
What are the causes of sea level change?
- climate gets colder, start of glaciation, more snowfall converted into ice, water stored in ice and doesn’t return to the sea -> worldwide sea level fall = eustatic change
- the weight of new glaciers causes the land to sink -> isostatic change which moderates eustatic change
- climate warms and ice starts to melt, water returns to ocean and sea levels rise worldwide = eustatic change
- ice melts from land and land starts to rise = isostatic readjustment, sea levels rise at the same time
How have temperatures changed recently?
Average temperature has risen by 0.6 degrees over the last 130 years - global warming. Resulted in a sea level rise of 10-15cm in last 100 years
How does tectonic activity have an impact on sea levels?
- uplift of mountain ranges and coastal land at destructive and collision plate boundaries that results in sea level fall
- local tilting of land at destructive margins eg. Mediterranean ports have been submerged
- movement of ocean due to earthquakes results in vast amounts of energy being transferred by waves to the coast, resulting in rapid erosion
