Glaciers - Exam 2 Study

Front 1

How does glacier ice form?

Back 1

Compaction of Snow

Front 2

Describe how compaction of snow occurs?

Back 2

Steady accumulation of snow over time squeezes air out of snow crystals and gradually compacts them until they become ice.

Note: This is different from the formation of ice cubes in a household freezer.

Front 3

Where will glaciers only form?

Back 3

Above a permanent snowline.

• Only here will snow last through a fall summer without melting completely.
• So only here will snow accumulate year after year and allow glacier ice to form.

Front 4

How does the height of the permanent snowline vary?

Back 4

It will vary according to climate:

1. How much snow falls in the winter.
2. How warm does it get in the summer.

Front 5

What two locations is their a permanent snowline?

Back 5

1. At very high elevations close to the equator.
2. At the sea levels close to the poles.

Front 6

Where can it also be said glaciers form?

Back 6

In locations with high:

• Altitude
• Latititude

Front 7

What are the two basic types of glaciers?

Back 7

Continental Glaciers (ice sheets)

Alpine (mountain) Glaciers

Cirque Glaciers

Valley Glaciers

Front 8

Define: Continental Glaciers

Back 8

Large Ice Sheets

Such as those found in Greenland and Antartica

Front 9

How large can Continental Glaciers be?

Back 9

• Large enough to cover over the underlying topography.

Example: Antarctica

Front 10

Define: Alpine (mountain) Glaciers.

Back 10

• Smaller than Continental Glaciers

• Found in high altitude locations

• Consists of cirque glaciers and valley glaciers

Front 11

Define: Cirque Glaciers

Back 11

• Form in high mountain basins

• Feed Valley Glaciers

Note: In the same way that small tributary streams feed larger rivers.

Front 12

Which two zones do Alpine Glaciers consists of?

Back 12

1. Ablation Zone
2. Accumulation Zone

Front 13

Define: Ablation Zone

Back 13

Mass loss through melting and other processes.

Front 14

Define: Accumulation Zone

Back 14

Mass gain from snowfall, wind-blown snow etc.

Front 15

What determines which zone an alpine glacier will consist of?

Back 15

By which process is dominant over the course of a year.

Front 16

What are the Ablation and Accumulation zones separated by?

Back 16

The Equilibrium Line

Front 17

Define: The Equilibrium Line

Back 17

Where mass gain and mass loss are equal.

Front 18

What two ways do glaciers move?

Back 18

1. Internal Flow
2. Basal Slip

Front 19

Define: Internal Flow

Back 19

• Involves the alignment of ice crystals so that they slide over each other down-slope.
• Happens under the influence of gravity, where glacier ice is under enough strain (usually from the weight of overlying ice).
• Deforms plastically, this is what allows internal flow to occur.

Front 20

Define: Plastic Flow

Back 20

• Occurs within the ice.
• Behaves under pressure as plastic material.
• Imagine a slow moving plastic stream.

Front 21

Define: Basal Slip

Back 21

• Where the whole glacier slides down-slope.
• Happens under the influence of gravity.
• Helped by the lubricating later of melt-water at glacier's base.
• Important process in summer.

Front 22

What is the movement of glaciers referred to as?

Back 22

Flow

Front 23

Is ice near the surface under much strain?

Back 23

No, there is not must overlying ice.

• It does not deform plastically.
• Rather, it is brittle and therefore cracks easily.

Front 24

What are the cracks near the surface of a glacier known as?

Back 24

Crevasses

Front 25

Where do Crevasses form?

Back 25

Wherever the stresses at the surface of a glacier exceed the ice's ability to deform.

Front 26

What is the best example of where Crevasses form?

Back 26

Where a glacier drops over a steep step.

• This causes ice to accelerate and pull away from the ice further up-glacier
• This forms a jumble of crevasses known as an icefall.

Example: The Khumbi icefall on Mt. Everest.

Front 27

What are two glacial erosion processes?

Back 27

1. Plucking (Lifting of Rocks)
2. Abrasion

Front 28

Define: Plucking

Back 28

• Ice Melts on the up-glacier side due to increased pressure.
• This liquid water flows around obstacles.
• Liquid water refreezes on the down-glacier side due to reduced pressure.
• This refreezing attaches bits of rock to the glacier.

• These bits are then plucked out as the glacier continues to flow down-slope.

Front 29

What is a classic example of plucking?

Back 29

The Roche Moutonnee

• A landform produced by relegation flow.

Relegation Flow

• Smooth up-glacier side
• Rough down-glacier side

Front 30

Define: Abrasion

Back 30

Particles within the ice act like sandpaper to smooth and polish the surface below.

Note: Works just as it does with rivers and with wind.

Front 31

Before Preglacial

During Post Glacial

After Post Glacial

Back 31

Front 32

What six characteristic landforms do Alpine Glaciation produce?

Back 32

H.A.C.T.H.H.

1. Horns
2. Aretes
3. Cirques
4. Truncated Spurs
5. Hanging Valleys
6. Hanging Waterfalls

Front 33

Define: Horns

H. A.C.T.H.H.

Back 33

• Steep walled peaks
• Created by several glaciers eroding back different sides of the same mountain.

Front 34

Define: Aretes

H. A. C.T.H.H.

Back 34

Created when two glaciers on opposite sides of a mountain erode back toward each other far enough to leave a narrow ridge between them.

Front 35

Define: Cirques

H.A. C. T.H.H.

Back 35

Bowl-shaped depressions that eroded out at the head of glaciers.

Front 36

Define: Truncated Spurs

H.A.C. T. H.H.

Back 36

Ridge that descends toward a valley floor from a higher elevation.

Front 37

Define: Hanging Valleys

H.A.C.T. H. H.

Back 37

• Tributary floor whose floor is at a higher level than that of the main valley due to recently glaciated areas.

Front 38

Define: Hanging Waterfalls

H.A.C.T.H. H.

Back 38

Front 39

Define: Till

Back 39

Material that is deposited directly by the ice.

Front 40

What two forms does glacial deposition take?

Back 40

1. Moraines
2. Outwash

Front 41

Define: Moraines

Back 41

• Layers or ridges of till
• Produced by Alpine Glaciers

Front 42

What are some features included in Moraines?

Back 42

• Terminal Moraines
• Lateral Moraines
• Pro-Glacial Lakes

Front 43

Define: Lateral Moraine

Back 43

• When valley glaciers start melting and depositing all the valley sediment they pick up along the way.
• That sediment is deposited as long ridges of till.

Front 44

Define: Pro-Glacial Lake

Back 44

Formed by either the damning action of a moraine or ice damn during the retreat of a melting glacier.

Front 45

Define: Terminal Moraine

Back 45

Till sediments that were deposited by glaciers during their greatest advance stage.

Front 46

Define: Outwash

Back 46

Glacial Deposition process in which material:

• Is carried away from the glacier by melt-water streams...
• Then deposited away from the glacier.
• These streams become braided due to their sediment load.

Front 47

What are the four features of glacial deposition left behind by large ice sheets (continental glaciers)?

Back 47

1. Eskers
2. Drumlins
3. Kettle Lakes
4. Outwash Plains

Front 48

Define: Eskers

Back 48

Long sinuous ridges of stratified drift that meander and have tributaries.

Front 49

Define: Drumlins

Back 49

• Smooth, elongated, parallel hills.
• Steep side faces the direction from which the ice advanced.
• Occurs in clusters called drumlin fields.
• Formation not fully understood.

Front 50

Define: Kettle Lakes

Back 50

Front 51

Define: Outwash Plains

Back 51

Front 52

What glacial features are in the US and where are they?

Back 52

Depositional

In the Midwest

Erosional

Yosemite Valley

Front 53

What is unusual about the glacial features in the US?

Back 53

There are now no glaciers in those places.

Front 54

What can we deduce from the presences of glacial features in the US but no glaciers?

Back 54

Climate must have been different in the past.

Note

The generally-accepted picture is that large glaciers were at their greatest extent around 18,000 BP.

Front 55

When was the Glacial Maximum?

Back 55

18,000 BP

Front 56

What did Glacial Maximum include?

Back 56

The greatest extent of the Laurentide ice sheets in North America.

Front 57

What else was happening around the time of the Glacial Maximum?

Back 57

Lake Bonneville and other western us Paleolakes were also forming.

Front 58

Was there only one cold period in Earth's history - 'The Ice Age'?

Back 58

No. The glacial maximum was just one cold period among many throughout earth's history.

Note: The term 'Ice Age' is therefore inappropriate.

Front 59

Define: Ice Age

Back 59

Technically an ice age is when Earth has ice at the poles.

Note

We're still in an ice age now.

Front 60

How often has earth undergone temperature cycles?

Back 60

Many times, both...

• Glacial (cold periods) and
• Interglacial (warm periods)

Note: Roughly one cycle (cold and warm) every 100,000 years.

Front 61

What is the main cause of climate change?

Back 61

Variations of Earth's orbit.

Note: Most certainly the trigger for glacial and interglacial cycles.

Front 62

Can smaller climate fluctuations occur within the larger patterns?

Back 62

Yes.

Example

• Even though Earth was warming up from 15,000 BP...
• It still underwent a short-lived but powerful cold phase
• Even as Earth got (overall) warmer.