Glaciation & Permafrost Flashcards
what is a glacier?
a slowly moving mass of snow and ice formed by the accumulation and compaction of snow on mountains or near the poles, found in a mountainous area
what is the higher accumulation zone?
where the snow accumulates at the top of the mountain
what is the lower ablation zone?
where the snow melts and sublimation occurs
what is moraine?
moraine is the eroded ground material that comes from the ground which the glaciers travel over
how does a glacier form?
they form as snow and ice that hasn’t melted completely before next year’s snow falls on top of it, the thickness increases each year and as the depth and weight increases, the bottom layers compress and recrystallise
where do glaciers tend to form?
in deeper valleys that do not get much warming from the Sun, at higher elevations where the temperature is lower
how do glaciers tend to move?
very slowly downhill - they tend to slide down existing valleys, forming valley glaciers
what will happen if a glacier reaches open water before it melts?
it will try and float, and icebergs will probably break off
what is a continental ice sheet?
if the temperature is low enough, ice can build up sufficiently and so much so that it is not confined to the valleys and becomes thicker than the highest mountains
why is there a temperature gradient in a glacier? why is it warmer at the base than it is at the top?
because heat from the Earth’s core rises which is why you sometimes get lakes beneath the ice (as the ice has melted) so you get a layer of liquid water making the glacier move downhill quicker as it is no longer frozen to the ground
what is a cold based glacier?
a glacier whose base is frozen to the ground it sits on, and the ice moves downhill only through internal shear – it flows slowly (plastic flow)
what is a warm-based glacier?
a glacier that has a warm base, it often sits on liquid water that moves very quickly downhill (basal slip)
what shape valleys do glaciers produce (through erosion)?
U-shaped valleys, with wide gentle curvature
what are striations?
gouges made in rock (usually lines) made by the passing ice over it - the lines are usually in the direction of movement
what forms when glaciers go round corners/or over ridges?
the ice distorts and crevasses are produced
