Landscape Evolution to Environmental Change Flashcards
What has happened to sea level since the Eocene?
Declined constantly
Which is denser oxygen 18 or oxygen 16?
Oxygen 18
What does it mean if oxygen 18 is denser?
It is harder to evaporate
What happens to oxygen 18 and oxygen 16 during glacial periods?
During glacial periods temperatures are not high enough to evaporate oxygen 18 due to its density. This means that only oxygen 16 is and so when water is taken from the oceans and then water falls forming glaciers it is composed of mostly the oxygen 16 isotope
During glacial periods is there more or less oxygen 18 found in ice cores from glaciers?
less
What does the information gathered form glacier ice cores tell us about sea level?
During glacial periods it was colder which means the sea level was lower and vice versa
What is a major complication of determining sea level?
Land level also changes
Today is the sea level relatively high or low?
High
What is asthenosphere migration?
During glacial periods the ice exerts large amount of pressure on the asthenosphere directly below it. This causes it to migrate laterally to areas of less pressure thereby causing it to uplift
What is post glacial rebound?
Following the melting of ice created during a glacial period the pressure directly below it is directly reduced which means the asthenosphere begins to migrate back under the area that had the ice above it.
What happens to the margins during post glacial rebound?
They subside as they loose the parts of the asthenosphere that had migrated there following the ice forming
What happens to the oceans during post glacial rebound? What impacts does this have on the equatorial and polar regions?
they receive large amounts of meltwater which causes the asthenosphere below to subside. this allows not only the poles to rise but also the equatorial regions as they receive more asthenosphere.
Which parts of the oceans subside during post glacial rebound?
Between the Arctic and Equator as well as between the Antarctic and Equator
What is happening to South Africa?
the land below is being uplifted due to the asthenosphere below the Indian and Atlantic Oceans subsiding after the last glacial period and flowing under the continent.
What are the precipitation changes expected through climate change?
Increased precipitation due to warmer temperatures will affect vegetation and thermohaline circulation
What impact will altered vegetation distribution have on the landscape?
There will either be more or less vegetation in areas which may lead to changes in the bank strength etc.
What did Schumm argue in relation to WM Davis’ model of landscape evolution?
That his model was too smooth and that in reality there were much more complex and intermittent stages. These changes are particularly evident from the landforms created through glacial periods
What are terraces?
During glacial periods ice masses scour and carve out the landscape which generates large amounts of sediment. This is then transported downstream through glacial flows. However, the river transport capacity is insufficient for this amount of sediment and so glacial fan deposits occur. When the ice melts the river transport capacity increases and so the sediment can be transported easier and so erodes the previous landforms creating terraces/
What are terraces an indication of?
How temperature, instead of uplift can determine the landscape evolution that WM Davis did not consider in his model
What are fluvial knickpoints?
When the water flows over a vertical drop and undercuts that structure. This can retreat back along the long profile altering the base level and eventually reaching an equilibrium set across previous waterfalls that encountered the same resistance.
How can fluvial knickpoints be sustained in their position?
the balance between their retreat and uplift
What are knickpoints an indication of?
How base level can change in a way not considered by WM Davis’ model of landscape evolution
