Lesson 6

Question 1

Glacier

Answer 1

• A glacier is a mass of relatively slow moving ice created by the long term accumulation of snow.

Question 2

Firn

Answer 2

• After about two winters, residual snow turns into what’s called firn. An intermediate state between snow and glacier ice.

Question 3

Sintering

Answer 3

• Here, water refreezes, binding snow crystals together and enlarging the individual grains. This process is called sintering.

Question 4

Dry Snow Zones

Answer 4

• But the transformation of snow into glacier ice can occur in the absence of water as well. Particularly, in what’s called dry snow zones
o Dry snow zones exist at some of the world’s highest elevations, and on the largest polar ice sheets.
o Under these conditions, the transformation of snow to glacier ice, instead, results from the mechanical breakdown of snow crystals as they’re blown around by the wind. And broken into smaller rounder, grains. Smaller rounder grains pack together much more efficiently. Further compaction leads to tighter assemblage of crystals, crystal growth, and sintering.

Question 5

What 3 factors determine how fast a glacier can be created?

Answer 5

1. ) Climate
2. ) Air Temperatures
3. ) Precipitation

Question 6

Ice Sheets

Answer 6

• An ice sheet is a massive glacial land ice extending more than 50,000 square kilometers. And because of their great dimension, their flow is completely independent of the topography beneath.

Question 7

Ice Caps

Answer 7

• Icecaps are miniature ice sheets covering less than 50,000 square kilometers.
• They form primarily in the polar and sub-polar regions that are usually high in elevation.

Question 8

Ice Divide

Answer 8

• The dome of an icecap is usually centered on the highest point of the massive, and ice flows away from this high point which is sometimes called the ice divide towards the icecap’s periphery.

Question 9

Mountain Glaciers

Answer 9

o Unlike ice sheets or icecaps, mountain glaciers are confined by the topography of the landscape in which they reside.

Question 10

Ice Field

Answer 10

• The largest type of mountain glacier is an ice field. At first glance, an ice field looks a lot like an icecap. But there’s one important difference. Unlike an icecap, the flow of an ice field is constrained by the underlying topographic features.

Question 11

Valley Glaciers

Answer 11

• Take a look at the icefield from above. From this vantage, it’s easy to see the network of long glaciers that fall away from the high basin and spill down the valley.
• These glaciers, which look very much like giant tongues, are called valley glaciers. Because they originate from an ice field, they’re also sometimes referred to as outlet glaciers.

Question 12

Piedmont Glacier

Answer 12

Piedmont glaciers occur when steep valley glaciers spill into a relatively flat plain, they fan out into bulblike lobes.

Question 13

Tidewater Glacier

Answer 13

• Tidewater glaciers are valley glaciers that flow far enough to reach out into the sea, like this spectacular glacier, the Columbia Glacier in the Chugach Mountains, which lie further north and west of the Saint Elias Mountains in southern Alaska.

Question 14

Calve

Answer 14

• As the ice reaches the sea, pieces break off, or calve, forming small icebergs.

Question 15

Hanging Glaciers

Answer 15

• Finally, when a major valley glacier system retreats and thins, sometimes tributary glaciers are left in smaller valleys high above the shrunken central glacier’s surface.
o These are called hanging glaciers and these glaciers often terminate at or near the tops of cliff bands.

Question 16

Cirque Glaciers

Answer 16

• Much smaller than valley glaciers are cirque glaciers. Cirque glaciers are named for the isolated bowl-like hollows or basins they occupy, which are called cirques.

Question 17

How is Material primarily moved?

Answer 17

1. ) Surface Melting
2. ) Evaporation
3. ) Calving

Question 18

Annual Input

Answer 18

material added

Question 19

Annual Output

Answer 19

material removed

Question 20

The difference between the input and the output is the….

Answer 20

annual net balance, or mass balance.

Question 21

Positive Mass Balance vs. Negative Mass Balance

Answer 21

• Positive mass balance will cause the glacier to grow and advance, while a negative mass balance means the glacier will shrink and retreat.

Question 22

Steady State

Answer 22

• In a steady state, the mass balance over the course of a year equals glacier’s equilibrium and the glacier remains roughly the same size.

Question 23

Accumulation Zone

Answer 23

nowfall often occurs at the greatest quantities at higher elevations where the temperatures are coldest.
o We call this area the accumulation zone. Here, annual inputs exceed outputs, and the mass balance is positive.

Question 24

Ablation Zone

Answer 24

• Further down the glacier, where it’s warmer at lower elevations, outputs in the form of melting and evaporation exceeds the inputs.
o This is the ablation zone. Here the annual mass balance is negative.

Question 25

Equilibrium Line Altitude (ELA)

Answer 25

Between the accumulation and ablation zones, a balance is reached where snowfall equals snow melt and the glacier is said to be an equilibrium.
• The average height where this occurs is called the Equilibrium Line Altitude or the ELA.

Question 26

Syeinn Palssen and Ogives

Answer 26

He climbed a big ice covered volcano and looking down onto one of it’s outlook glaciers, observed the prominent arcuate or bow-shaped bands that have since come to be known as ogives.

Question 27

Terminus

Answer 27

end of the glacier or its snout.

Question 28

Basal Sliding

Answer 28

• Another major mechanism involved in glacier movement is basal sliding, which involves the slippage of ice on mass over the rock surface at its base.

Question 29

2 Controls for Basal Sliding

Answer 29

1. ) Temperature of ice at the base

2. ) Presence of water to serve as lubricant

Question 30

Bed Deformation

Answer 30

• If the bed surface underneath the glacier isn’t solid rock, if it’s loose sediments or soils for example, the presence of water can substantially weaken the bed. And this makes it easier for the glacier to deform the sediment beneath it rather than to move along on top of it. And this introduces a third mechanism that contributes to glacier flow, bed deformation.

Question 31

What three things is Ice Deformation driven by?

Answer 31

1. ) Gravity
2. ) Thickness of the ice
3. ) Slope Angle

Question 32

Little Ice Age

Answer 32

• The great cultural shift in our understanding of glaciers and ice all happened during what we might call a glacier high tide in the Alps. It was a short period of time, a window when most of the world’s glaciers were actually advancing.
• We now call this period the Little Ice Age. And it lasted from around 1500 to 1850, three and a half centuries in all. Ending abruptly during the height of the industrial revolution.

Question 33

Crevasses

Answer 33

• Crevasses are deep cracks or fractures found in the glacier, as opposed to crevices which form in rock.

Question 34

Moraines

Answer 34

• Another noticeable surface feature of mountain glaciers is the linear accumulation of rocky debris oriented in the direction of the flow. These are called moraines, and they’re created when the glacier pushes or carries rocky debris as it moves.

Question 35

Glacial Valley

Answer 35

• Common all over the world on a large scale, glaciated valleys are probably the most readily visible glacial landform. They’re trough shaped, often with steep, near-vertical cliffs, where entire mountainsides were scoured by glacial movement

Question 36

Aretes

Answer 36

• Aretes are jagged narrow ridges created where the back walls of two glaciers meet, eroding the ridge on both sides.

Question 37

Horns

Answer 37

• Horns are created when several cirque glaciers erode a mountain, until all that’s left is a sharp pointed peak, with sharp ridge-like aretes, leading all the way to the top.

Question 38

Saddle/Notch

Answer 38

• When cirque glaciers develop on opposite sides of a ridge, they erode headward and eventually meet to create a saddle or notch in the ridge crest. This also tends to reduce the thickness of the ridge.