Studied by 0 people2b on the spec: -the physical factors which influence the formation of landforms within the landscape system -the inter-relationship of a range of landforms within the characteristic landscape system -how and why the landscape system changes over time from millennia to seconds, such as rock fall in seconds, seasonal changes in deposition rates and erosion of basins over millennia
What are the physical factors that influence the formation of landforms?
Climate, geology, latitude, altitude + aspect
How does the climate influence the formation of physical landforms?
If the climate hadn’t changed originally, there wouldn’t have been any ice → ice sheets wouldn’t have formed + no landforms would be there in the first place
eg. the proglacial lake Lake Agassiz that meant that the River Warren could form
How does geology influence the formation of physical landforms? (erosive speeds)
There are different types of rocks in Minnesota → different speeds of erosion
eg the Arrowhead region in the north-east where the erosional basin was deep and so weak shale rocks were exposed that eroded more rapidly than the surrounding resistant volcanic rocks
How does geology influence the formation of physical landforms? (till)
There are different types of sediment in different areas → causes the till deposited by the ice sheet to be different depending on where the ice sheet has come from
Where did the Wadena Lobe come from + what sort of till did it deposit?
It advanced from north-east Canada
The till is red and sandy
Where did the Des Moines Lobe come from + what sort of till did it deposit?
It advanced from the north-west of Minnesota
The till is tan-coloured and clay-rich
How does latitude influence the formation of physical landforms?
The ice sheet could only move to 37°N → caused the southern part of Minnesota to have a more varied landscape as it was not crushed by the ice sheet
How does altitude influence the formation of physical landforms?
Not much of an impact → different heights of mountains are all obliterated by the ice sheet: Laurentide ice sheet was over 1,000m thick in places
→ highest mountains now are 500-700m
How does aspect influence the formation of physical landforms?
It doesn’t :)
Which ice sheet was in Minnesota?
Laurentide ice sheet
Inter-relationship: ellipsoidal basins
Erosion by the Laurentide ice sheet produced a series of ellipsoidal basins → in Minnesota, the Upper and Lower Red lakes are in an ellipsoidal basin
Inter-relationship: till sheets
In Minnesota, lots of till sheets were formed by deposition during the retreat of the Laurentide ice sheet (made up of till from Wadena Lobe, Des Moines Lobe etc)
Inter-relationship: proglacial lakes
Proglacial lakes formed when the edge of the ice sheet formed a dam + creates a number of proglacial lakes
Largest proglacial lake: Lake Agassiz - covered 440,000km
→ Lake Agassiz isn’t there any more but the river that drained from it is called the Glacial River Warren
→ the water that flowed out of Lake Agassiz carved out the Minnesota River Valley (up to 5 miles across in some places)
Landscape changes over time: fastest (diurnal/seconds)
-rock fall + weathering adding debris to ice sheet
Landscape changes over time: longest
-erosion creating ellipsoidal basins
Note
Flashcard