Isostatic And Eustatic Change Flashcards
Evidence for long term sea level change
In the past, over much longer time scales, sea levels have varied enormously compared to their current position. During the Quaternary period, there were several alternating cold (glacial) periods, during which sea level fell, and several warm (interglacial) periods, during which sea levels rose, in response to the nature of precipitation
What are the main 2 causes of sea level change
Eustatic change - when the sea level itself rises or falls
Isostatic change - when the land rises or falls, relative to the sea
What is eustatic change?
Eustatic change ie global. In cold glacial periods, precipitation falls as snow (rather than rain ) and forms huge ice sheets that store water that is usually held in the oceans. As a result, sea levels fall. As temperatures rise at the end of glacial periods, the ice sheets begin to melt and retreat. Their stored water then flows into the rivers and the sea, and sea levels rise.
What is isostatic change?
Isostatic change occurs locally. During glacial periods, the enormous weight of the ice sheets (which can be several kilometres thick) makes the land sink- isostatic subsidence. As the ice begins to melt at the end of a glacial period, the reduced weight of the ice causes the land to readjust and rise- isostatic recovery. This is the explanation for the landscape with the various coastal landforms stranded above the current high-tide line
UK land changes due to isostatic change
- land in the North and west (which was covered by ice sheets during the last Ice Age) is still rising as a result of isostatic recovery. It is along these coastlines that features of falling sea level are most evident
- land in the south and east (which the ice sheets never covered) is sinking. Rivets pour water and sediment into the Thames Estuary and the English Channel.
The weight of this sediment causes the crust to sink and relative sea levels to rise. Therefore, south- east England faces increased flood risks notonly as a result of isostatic change, but also because of a rising sea level caused by global warming. It is along parts of the south of England where there are features associated
Sea level change due to past tectonic activity
This past tectonic activity has had a direct impact on Some costs across the world as well as on sea levels
The uplift of mountain ranges in coastal land at destructive and collision plate margins that resulted in A relative fall in sea level in some parts of the world
Local tilting of land at destructive margins for example Some ancient mediterranean ports have been submerged and others have been stranded above the current sea level
How are fjords formed
They are formed when deep glacial troughs are flooded by rise in sea level. They are long and steep sided, with a U- shaped cross section and hanging valleys. Unlike rise, fjords are much deeper inland than they are at the coast. The shallower entrance marks where the glacier left the valley. Fjords can be found in Norway, Chile and New Zealand
How are Rias formed?
Rias are formed when valleys in a dissected upland area are flooded? Rias are common in south-west England, where sea levels rose after the last Ice Age- the lower parts of many rivers and their tributaries were drowned to form Rias.
What are raised beaches
As the land rose as a result Of isostatic recovery formal wave cut platforms and their beaches were raised above the present sea level raised beaches are common on the West Coast of Scotland where the remains of eroded cliff lines (called relic cliffs) can often be found behind the raised beach with wave cut notches and caves as evidence of past as evidence of past marine erosion Wave cut platforms can also be exposed if sea levels fall sufficiently although these are often hidden beneath fresh beach deposits
Dalmatian coasts
Dalmation coasts are distinctive submergent coastlines that form in a landscape of ridges and valleys running parallel to the coast.
when the sea level rises, the valleys flood although the tops of the regions remain exposed forming a series offshore islands running parallel to the coast
dalmation coasts are also known are also known as Pacific coasts for example in Southern Chile
Recent and predicted climatic change and potential impact on coasts
According to the intergovernmental panel for climate change sea levels Stabilised about 3000 years ago 3000 years ago and they have changed little since that time until very recently from the late 19th century to the late 20th century sea levels rose globally by about 1.7 mmeters per how many millimetres per year although this has increased to about 3.2 mmeters per year in the period of 1993 to 2013.
Sea level rise is the result of primarily of sun primarily of salmon expansion of water due to to heating and the melting of fresh water ice such as the green land and Antarctic ice sheets and mountain glaciers between 1818 80 and 2010 global temperature is rarely spanned average of Is 0.85ﾟC
The impact of climate change on Kiribati
The nation consists of 33 islands in the Pacific ocean, that stretch across an area almost as wide as the USA. Kiribati’s islands are very low lying sans and mangroves atolls- in most places onlyaamtre or less above sea level, it has been predicted that many of its islands could disappear under the sea in the next 50 years. In places, the sea level is rising by 1.2cm a year .
Rising sea levels in Kiribati are contaminating its groundwater sources and affecting its ability to grow crops.
The president bought an island in Fiji for agriculture and fish farming g projects instead.
