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The Landscape of Ice Sheets in Minnesota - Coggle Diagram
The Landscape of Ice Sheets in Minnesota
Geology:
Landscape is part of the
Laurentian Shield
Oldest rocks lie in alternating rocks (northern half)
Volcanic + sedimentary rocks, granitic rock materials lie in areas around the belt
Metamorphic gneiss, crops out along the
Minnesota River Valley
Volcanic formations lie throughout
Laurentian Shield
Some buried beneath
glacial deposits
Erosional Impact:
Laurentian
ice sheet + ice lobes
had a massive erosional impact on the landscape
High mountains worn down
Ellipsoidal basin
created; now studded with thousands of lakes eg. upper/lower red lakes
Arrowhead:
Erosional basin was particularly deep
Earlier tectonic tilting exposed weak shale rocks which eroded more rapidly than the resistant volcanic rocks around them
Depositional Impact:
Till
deposited by
Wadena Lobe
is red and sandy (derived from red sandstone + shales to N +NE)
Ground moraine
with reddish iron-rich sediments extends from
St Cloud
north-eastward
Glaciers produced formed
terminal moraines
(extend from NW to
Minneapolis
and
St Paul
)
Last advance left a
course - textured till
(abundant fragments of granite, slate, red stone)
Minnesota USA:
Present landscape - resulted from the last quaternary period (+ and - of several successive periods of continental ice sheet activity)
Ice Sheet Lobes
:
Responsible for some of the regional variations found within
Minnesota
Appear at the fringes of an ice sheet as it spreads out
Proglacial Lakes:
Proglacial Lakes:
Lobes, edge of ice sheet, damn the natural drainage area
Lake Agassiz:
Glaciers to the north block drainage
South of ice, lakes formed when ice melted