GLACIATION Glacier – typically slow moving mass of ice (formed by recrystallization of snow).

Snow firn (neve) glacier ice flakes small granules “dense” ice of ice

Fig. 12.4a

Fig. 12.5

Fig. 12.4b

Fig. 12.6

Movement of glaciers is –

Slow (1inch to 30 feet per day) and depends on:

1. temperature 2. slope

Plastic flow due to high pressure Surging can occur.

Box 12.2.1

Fig. 12.8

Fig. 12.9b

Fig. 12.9a

Work of glaciers –

1. transport material

2. ice wedging

3. erosion

3. Erosion

a. quarrying (plucking)

b. abrasion

i. rock flour ii. rock polish

iii. grooves iv. rock striations

Fig. 12.13

Fig. 12.22

Load of glaciers –sediments carried:

a. on top b. along the sides c. on the bottom d. within the ice

Fig. 12.12

Fig. 12.19

Glacier ice DOES NOT SORT material.

Types of Glaciers

1. Alpine (Mountain-Valley) 2. Continental

Glacial Features:

A. Erosional

B. Depositional

Fig. 12.2

Fig. 12.1

Fig. 12.15

Fig. 12.14

A. Erosional 1. cirque 2. horn 3. tarn 4. arête 5. hanging valley 6. “U” – shaped valley

Fig. 12.18

Fig. 12.17c

Fig. 12.20

Fig. 12.21

Fig. 12.16

A. Erosional

1. cirque 2. horn 3. tarn 4. arête 5. hanging valley 6. U-shaped valley

A L P I N E

B. Depositional 1. unstratified = till

material deposited directly by glaciers

2. stratified

Depositional 1. unstratified

a. moraines i. terminal

ii. recessional iii. lateral iv. medial v. ground

b. drumlins

Fig. 12.25

Fig. 12.26

Fig. 12.27

Fig. 12.24

Fig. 12.29

2. Stratified

a. Outwash plain b. Kettle c. Esker d. Kame e. varve

Fig. 12.28

Fig. 12.31

Fig. 12.30

Causes of Glaciation

1. Decreased carbon dioxide content of the atmosphere

2. Volcanic action

3. High continents

4. Changes in salinity of the ocean resulting in changes in ocean currents.

5. Shift in position of the continents

6. Astronomic theories a. Cosmic dust cloud b. Earth-sun distance varied

c. Radient heat from the sun varied.

Effects of Glaciation

1. Bare rock in northern Canada (shield area).

2. Glacial material deposited in northern USA

3. Arrangement of drainage patterns of the Missouri and Ohio Rivers

4. Sea level change (e.g., Hudson Bay and Lake Michigan)

Isostacy – “vertical

movement of Earth’s crust in order to maintain equilibrium. Melting ice causes land to rise.

5. Formation of the Great Lakes due to: a. Isostacy

6. Sea level changes

7. Changes in climate (e.g., Texas was a lake area during the Ice Age)

8. Reminants of ice sheets today.

Fig. 12.33

Fig. 12.34

Box 12.7.1

Fig. 12.7a

Fig. 12.7b

Varves

Fig. 12.32

The Ice Age