Glaciation in the UK Flashcards
All 10 cards in this deck
How far south did ice reach across the UK at its maximum extent in the last ice age?
Ice covered all of Scotland, Wales, Ireland and northern England, reaching a line roughly from the Bristol Channel across to the Thames Estuary/Norfolk. Southern England stayed ice-free.
True or false? During the last ice age the ice sheet was deeper over the British Isles than over Scandinavia.
False. It was much deeper over Scandinavia (over 2500 m) than over the British Isles (just over 1500 m).
What are the steps of freeze-thaw weathering?
e.g. on a bare rock face above a glacier- Water collects in a crack in the rock — e.g. meltwater fills cracks in the rock face.
- Temperature falls below 0°C; the water freezes and expands by about 9%, widening the crack.
- Repeated freezing and thawing shatters the rock — angular scree falls onto the glacier.
What is abrasion by a glacier?
Rock debris frozen into the base and sides of the glacier is dragged over the bedrock, scraping and smoothing it like sandpaper (leaving striations).
What is plucking by a glacier?
Meltwater at the base of the glacier freezes onto the rock; as the ice moves it tears lumps of rock away, leaving a jagged surface.
What is rotational slip?
The circular, curved movement of ice within a hollow, which deepens the hollow into a corrie.
What is bulldozing by a glacier?
The snout of an advancing glacier pushes loose material in front of it forwards.
Why do glaciers deposit sediment?
When the ice melts the glacier loses energy and can no longer carry its load, so material is dropped — mostly at and beyond the snout.
True or false? Glacial till is unsorted but outwash is sorted.
True. Till is dropped straight from the ice as a mixed, angular, unsorted deposit; outwash is carried by meltwater, so it is sorted with finer material further from the snout.
True or false? Freeze-thaw weathering needs temperatures that repeatedly rise above and fall below 0°C.
True. Water must melt to seep into cracks and then refreeze and expand, so repeated crossing of freezing point is needed.