SG3B: Case study associated with the action of ice sheets: The Laurentide Ice Sheet and it's impact on the landscape of Minnesota, USA

Question 1

What is an ice sheet?

Answer 1

Large accumulation of ice burying landscape below.

Question 2

How far can an ice sheet extend?

Answer 2

50,000km squared

Question 3

Where are ice sheets found?

Answer 3

Antarctica and Greenland

Question 4

When did the Laurentide Ice Sheet exist?

Answer 4

During the Pleistocene ice age.

Question 5

Where was the Laurentide Ice Sheet?

Answer 5

It centred over what is now Hudson Bay and covered most of North America down to Minnesota.

Question 6

How doe ice sheets flow differently to valley glaciers?

Answer 6

In an ice sheet the ice flows outwards from the centre to the edges. Whilst a glacier the ice moves downhill from the upper part of the glacier to the lower part.

Question 7

What made up the laurentide ice sheet?

Answer 7

Several ice domes.

Question 8

What are ice domes?

Answer 8

Where ice accumulated and flowed outwards.

Question 9

How did the LIS impact mountains?

Answer 9

Massive erosional impact of the LIS wore down many mountains. The highest national point: Eagle mountain, Minnesota = 701m

Question 10

What is an ellipsoidal basin?

Answer 10

A huge basin.

Question 11

How is the ellipsoidal basin formed?

Answer 11

By the erosion of deep depressions in the bedrock by an ice sheet.

Question 12

What is the largest basin?

Answer 12

Hudson bay.

Question 13

Why is hudson bay the largest basin?

Answer 13

because ice here was the thickest - more pressure- more erosion.

Question 14

How did the Great Lakes System form?

Answer 14

The great lakes occupy former river valleys eroded by ice lobes. Ice lobes advanced and retreated many times forming smaller ellipsoidal basins (the great lakes).

Question 15

What is an ice lobes?

Answer 15

Are tongue shaped glaciers extending from the edges of the main ice sheet.

Question 16

What is the geology of the great lakes?

Answer 16

Mainly sedimentary rock e.g. limestone, shales and sandstone.

Question 17

What is so special about sedimentary rock?

Answer 17

Easier to erode, less resistant

Question 18

How were striations created by the LIS?

Answer 18

Subglacial debris on the bedrock under the ice sheet scours out striations on the bedrock as the debris moves with the ice sheet.

Question 19

Name an example of a striation?

Answer 19

Lake superior striations.

Question 20

What are the depositional landforms created by the LIS?

Answer 20

Till sheets
Moraines
Drumlins
Erratics 
Proglacial lake

Question 21

Why is the ice lobe named for a specific geographic area for the till?

Answer 21

The till deposited across minnesota has varying characteristics and materials depending on which lobe deposited the till and the origin of the lobe.

Question 22

What are the 3 ice lobes?

Answer 22

Wadena
Rainy and Superior
Des moines

Question 23

Where was the Wadena lobe?

Answer 23

The north of Minnesota

Question 24

What did the Wadena lobe deposit?

Answer 24

Red sandstone and shales

Question 25

Where was the Rainy and Superior lobes?

Answer 25

NE of minnesota.

Question 26

What did the rainy and superior lobes deposit?

Answer 26

Course- textured basalt, gabbros, granite.

Question 27

Where was the Des Moines Lobe?

Answer 27

Originated in the NW and advanced SE across Minnesota.

Question 28

What did the Des Moines lobe deposit?

Answer 28

Fine textured, buff to tan coloured, clay rich shale.

Question 29

What are the 4 moraines called?

Answer 29

• Alexandra Moraine
• St Croix moraine
• Altamont moraine
• Bemis moraine.

Question 30

Which lobe created the Alexandra moraine?

Answer 30

Rainy lobe

Question 31

Which lobe created the St Croix moraine?

Answer 31

Superior lobe

Question 32

Which lobe created the Bemis moraine?

Answer 32

Des Moines Lobe

Question 33

Which lobe created the Altamont moraine?

Answer 33

Des Moines lobe.

Question 34

Give an example of drumlins?

Answer 34

Drumlin fields across New York State and extending into the great Lakes.

Question 35

Give an example of erratics?

Answer 35

Three Maidens founded in SW Minnesota, Pipestone National Monument.

Question 36

What is a proglacial lake?

Answer 36

A body of water stored in front of a glacier or ice sheet.

Question 37

What is the largest proglacial lake?

Answer 37

Lake Agassiz.

Question 38

What is a mega flood?

Answer 38

When the ice melted, it overflowed the ice dam resulting in a mega flood.

Question 39

What are the physical factors that influence formation of landforms?

Answer 39

climate
lattitude and altitude
geology

Question 40

How did the climate influence the formation of the landforms?

Answer 40

Climate affects the glacial budget of a glacier controlling whether ablation favours over accumulation or vice versa e.g. Bemis Moraine.

Question 41

How did the attitude and altitude influence formation of landforms?

Answer 41

Lattitude and altitude affect the climate within a system which therefore can change the thickness of ice, competence levels and then the landforms developed.

Question 42

How does geology influence the formation of landforms?

Answer 42

Different types of rocks affect the landforms formation developed in glacial areas such as ice sheet. Example is the Great lakes.

Question 43

What are the short term changes of a landscape system?

Answer 43

Mass movement

Mega flooding

Question 44

What are the seasonal changes of a landscape system?

Answer 44

Advancing and retreating of ice sheet

Question 45

What are the millennia changes?

Answer 45

Formation of an ice sheet
Modification of landforms
Growth of the LIS