GL28 Laurentide Ice Sheet Review Flashcards
What is the Laurentide ice sheet?
The Laurentide ice sheet is an ice sheet that covered much of Canada and Northern USA at various points during the Quaternary Period (from 2 mya).
What was the extent and thickness of the Laurentide ice sheet in Minnesota?
The Laurentide ice sheet extended to 37°N and covered 13 million km2. It was up to 3000 m thick.
How did the climate affect the landscape in Minnesota during the Wisconsin glaciation?
The extended period of cold temperatures combined with continued precipitation in the Wisconsin glaciation 100,000-11,000 years ago led to the advance of the ice sheet up to 4 km thick. The ice sheet covered extensive areas, was not constrained to high altitude valleys, and had an extremely erosive impact on the landscape of Minnesota.
How does relief affect the landscape in Minnesota?
Highland areas diverted the lobes to follow low flat areas, which affected where glacial rivers such as the river Warren would have formed because meltwater would have flowed to lower regions.
How does the geology of the rock affect the landscape in Minnesota?
Geology affects rates of erosion through different resistances causing differential erosion. The north of Minnesota is part of the Laurentian Shield, which is underlain by alternating bands of resistant igneous rock and weaker sedimentary rock. The ice sheet eroded many pyramidal peaks in the hard igneous rock.
How did the Laurentide ice sheet affect the formation of ellipsoidal basins and lakes in Minnesota?
The movement of the ice caused erosion and the formation of ellipsoidal basins (Hudson Bay and Great Lakes). At the end of the glacial period, the weight of the ice being lifted caused isostatic readjustment which influenced landforms. The glacial period was interspersed with short warmer periods, causing the ice sheet to advance and retreat many times resulting in lobes depositing different tills.
What is the impact of geology on the landscape of Minnesota?
Created a knock and lochan landscape - Lake Vermilion and others in Arrowhead region as tectonics revealed weaker shale rock that was eroded more to create very deep lakes. Vermilion depth of 23m but others up to 60m deep. The southwest is sedimentary rocks such as shale and silt, and the southeast is sedimentary - limestone.
How did the glacial period in Minnesota end?
Temperature amelioration at the end of the glacial caused its retreat (12 kya) and formed giant proglacial lakes (Lake Agassiz – 440,000 km2) – outlet stream (Glacial River Warren) cut a large gap through Traverse Gap and formed alluvial deposits in the Red River valley.
