Glaciation SG1 Flashcards
What is the thick ice spread out over land and sea?
Ice Sheet
What are the rivers of ice which flow down from high mountains in the river valley?
A Valley Glacier
What is the cold phase where global temperatures dropped by approx. 5 degrees causing ice to spread?
Glacial Period
What is the warm phase where temperatures increased to present level or above?
Interglacial period
What are landscapes shaped by glaciers?
Glaciated landscapes
What is a relict landscape?
Places that were glaciated in the past
Where are the only two ice sheets in the world?
Antarctica and Greenland
What is the name of the last ice age?
Pleistocene
When was the most recent Ice Age?
2 million years ago - - 11,700 years ago
What % of the earth is currently covered in ice?
10%
What % of the earth was covered in ice 18,000 years ago?
30%
What % of the worlds ice is contained in ice sheets?
69%
What is basal sliding?
sliding of the glacier over bedrock in warm based glaciers where temperature exceeded pressure melting point and lubricates the surface
What is meant by regelation creep?
when the glacier moves over an obstacle (such as a large protruding rock) by melting as the ice moves up over the obstacle, providing lubrication enabling the glacier to slide
What is substrate deformation?
when meltwater seeps into the bedrock causing it to become statured and mud like which provides a lubricated plain for the glacier to slide over
What is extending and compressing flow?
due to different gradients of the valley floor, the glacier moves quickly in steeper sections and the ice things out (in flatter sections the glacier moves slowly and thickens)
What is internal deformation?
the overlying weight of the ice causes the ice near the base to be squashed
the ice crystals align and flatten so they move over each other by intergranular slip
What is the step by step order of how glacial ice forms? (6 steps)
1) Snow falls as flakes which have an open, feathery appearance and so can trap lots of air
2) Snow becomes compacted by the weight of later snowfalls
3) The increase in pressure on the buried snow also results in pressure melting and a tiny amount of meltwater forms between the snow crystals which then refreezes
4) More meltwater continues to fill the air passages and refreezes into bigger ice crystals
5) Snow that has survived the subsequent summer melting is called firn/nerve
6) Over time, and with depth, a solid mass of glacial ice forms (in Antarctica it can take 1000 years but in Alpine locations it can be as quick as 25-40 years)
What are the four points that applies to warm base glaciers?
High altitudes
Meltwater is present at the base
Move mainly by basal sliding and internal deformation
Temperature of ice at or above pressure melting point
Are glaciated landscapes open or closed systems?
Open
