Minnesota Ice sheet case study Flashcards
Name of the ice sheet that shaped the landscape of Minnesota?
Laurentide ice sheet
When did Laurentide ice sheet have most coverage across North America?
Quaternary period, 2.6million years ago.
Outline climatic variations in Minnesota depending on latitude.
North = 1km deep in places, more severe climate due to high latitude
South = 160m deep thickest
What is isostatic lowering?
Erosion due to high mass ice which lowers the landscape.
Eg. in Arrowhead region (NE) in Minnesota because of 1km thick ice in places in north
What is the significance of shale in Minnesota?
- Tectonic activity in North/ Arrowhead region
- Folding of rock
- Exposed shale (found deep underground, highly organic and not resistant)
- Contributed to the deepened ellipsoidal basin in Arrowhead
- Clay rich contributes to deposited Terminal Morraine from Des Moins Lobe in SW
Geological characteristics in southern Minnesota
- Sedimentary rock
- Low resistance
Geological characteristics in Northern Minnesota
Alternating belts of geology.
- Sedimentary then volcanic.
- In between belts is granite.
Why is ice thicker in northern Minnesota?
Harsher climate and severe cold and conditions.
What is Lake Aggasiz?
A 440km2 proglacial lake formed in Minnesota to the south of glacial ice because ice lobes blocked drainage channels.
- To the south of glacial ice.
Characteristics of arrowhead region.
- North East.
- Shale (uprisen from underground by tectonics and is not resistant).
- Low erosional resistance.
- Deep ellipsoidal basins.
- Isostatic lowering.
Examples of ellipsoidal basin, glacial lakes in Arrowhead region
Upper and Lower Red Lakes.
(remember because Wadena lobe deposits red and sandy in the NE)
Name the 4 ice sheet lobes in Minnesota
Wadena, Superior, Rainy and Des Moins.
What does Des Moins lobe deposit?
- Des Moins Lobe goes from NW to SW
- Clay rich because of tectonic activity in north, picking up shale.
What is the morraine formed by Des Moins lobe?
Terminal moraine called Prairie Coteau which is very clay rich
What type of geology does Wadena lobe deposit?
Red Sandstone
What feature is formed by the Wadena lobe in NE Canada?
Alexandra moraine drumlin field
- In Otter Trail.
What is isostatic readjustment?
Occurs during glacial retreat as the isostatic pressure decreases, causing an uprise in land, increasing elevation of the land.
