Glaciers Flashcards
when was the last glacial period in the uk?
around 20000 years ago
did ice cover all of the uk?
no. it went down to around Snowdonia
what is freeze thaw weathering?
freeze thaw weathering is a type of erosion that takes place in cold places like glaciers. it happens when water enters a crack in the rock during the warmer days, and then freezes during the night. water expands by 10% when it freezes so it gradually pushes the crack apart over many times of it feezing and being filled with water again, until it breaks off completely.
what is plucking/abrasion
plucking
-as the ice moves over the rock surface, meltwater below the ice freezes around loose sections of rock. this joins the rocks to the glacier and carries them away.
abrasion
-this is when rocks at the bottom of the glacier (often from plucking) scrape along the rock surface like sand paper.
what is a corrie and how does it form?
a corrie is a deep armchair shaped hollow in the side of a mountain and it is where a glacier begins.
it forms by snow collecting in a small hollow over time, and deepening and compressing to become a dense mass of ice. freeze thaw weathering and plucking pull away the surface of rock underneath. this helps with abrasion and the hollow gets deeper as the rotational slip of the ice erodes the rock. the wall retreats backwards due to more freeze thaw weathering and it is formed deep into a mountainside.
how does an arete form?
an arete forms when two corries develop side by side, with a ridge in-between them.
how does a pyramidal peak form and how does it differ to an arete?
when three or more corries grow into hollows on all sides of a mountain, a pyramidal peak is formed.
what is a truncated spur
when interlocking spurs are cut off by a glacier eroding through the middle, to leave truncated spurs
what is a glacial trough
a glacial trough is where the glacier has travelled through, the u-shaped valley.
what is a ribbon lake and where do they form?
a ribbon lake is a long , narrow lake that forms in the bottom of a glacial trough once the glacier has receded.
