Chapter 9: Ice and Glaciers, Wind and Deserts

Question 1

Glaciers

Answer 1

Masses of ice that move under their own weight, under the force of gravity. Typically form at high latitudes and/or high altitudes.

Question 2

How long does it take for glaciers to form?

Answer 2

can take several centuries to form (and melt)

Question 3

What conditions must be met for glaciers to form?

Answer 3

1) precipitation
2) a higher rate of snowfall than melt each year (allows glaciers to grow)
3) mountains (higher elevation → colder temperatures)
4) gentle slope

Question 4

Transformation of snow to glacier ice

Answer 4

A slow process that can take decades or thousands of years in which loose snow (90% air) compacts and become denser as air is driven out, and turns into firn. Then eventually recrystallizes to form glacial ice, which consists of interlocking ice crystals. Eventually gravity pulls the mass of ice downslope, creating a glacier.

Question 5

Alpine Glacier

Answer 5

numerous today also called mountain or valley glaciers, occurs at high altitudes

Question 6

Continental Glacier

Answer 6

Larger glaciers which are rarer today, typically occur near poles. can span entire continents and reach large thicknesses.

Question 7

How many continental glaciers exist today and where are they?

Answer 7

two main continental glaciers remain in present day
1) Greenland
2) Antarctic ice sheets

Question 8

Pleistocene Ice Age and Glaciers

Answer 8

During this time (2.5 Ma - 11,700 years ago) much of the northern hemisphere was covered in glaciers.

Question 9

Plastic Deformation

Answer 9

occurs at depths of 60 m in a glacier, ice grains change shape very slowly as the glacier moves, and/or new grains grow while old ones disappear.

Question 10

Crevasses

Answer 10

the cracks, when ice is too brittle to flow, and instead moves by cracking

Question 11

What depth does ice stop cracking?

Answer 11

ice does not crack below depths of 60 m: the 60 m boundary is the brittle-plastic transition

Question 12

Basal Sliding

Answer 12

the presence of liquid water or a wet slurry may appear beneath a glacier, reducing friction, and allowing the glacier to glide along the equivalent of a wet cushion of water.

Question 13

Why do glaciers move?

Answer 13

glaciers move due to gravity: glaciers flow in the direction in which their top surface slopes. Glaciers flow between 10-300 m/year

Question 14

Zone of accumulation

Answer 14

snowfall adds ice to a glacier

Question 15

Zone of Ablation

Answer 15

Ablation is the removal of ice
if temperatures at the terminus are warm, evaporation, or melting

Question 16

Three processes of zone of ablation

Answer 16

Sublimation, melting, calving

Question 17

Sublimation

Answer 17

evaporation of ice into water vapor

Question 18

Melting

Answer 18

transformation of ice into water

Question 19

Calving

Answer 19

breaking off of chunks of ice at the end of the glacier into smaller pieces

Question 20

Equilibrium line

Answer 20

The boundary between the zone of accumulation and the zone of ablation and defines whether a glacier grows or shrinks.

Question 21

Toe of glacier

Answer 21

The part of the glacier that advances - its leading edge

Question 22

Glacial Advance vs. Glacial Retreat

Answer 22

Advance glacier grows, retreat glacier shrinks

Question 23

Glacial Erosion and Deposition

Answer 23

glaciers can carve relief into mountainsides: their movement strips away topsoil and scrapes and scours the underlying bedrock as they travel over the surface of a continent

Question 24

V-shaped and U-shaped valleys

Answer 24

A V-shaped valley is carved out by a stream and U-shaped valleys are when glaciers erode and widen the sides of the valley and also its floor

Question 25

Glacial striations

Answer 25

the grooves/scratches in rocks left due to glacial activity, they form parallel to the flow direction of the glacier

Question 26

What does plucking refer to?

Answer 26

as a glacier moves it plucks parts of the neighboring mountainside

Question 27

Landforms on mountains (3)

Answer 27

Cirque: bowl-shaped depression that develops on the side of the mountain at the head of a glacier
Arête: knife-edge ridge of rock that separates two adjacent cirques
Horn: pointed mountain peak surrounded by at least three cirques

Question 28

Till

Answer 28

sediment transported by ice and deposited beneath, at the side, or at the toe of a glacier. The sediment is usually poorly sorted compared to stream-deposited sediment: glacial ice can carry clasts of all sizes.

Question 29

Outwash

Answer 29

When till mixes with meltwater

Question 30

Moraine

Answer 30

A pile of rock and dirt. The term is used to describe debris piles carried or left behind by glaciers

Question 31

Lateral Moraine

Answer 31

the side edge of the glacier, where two valley glaciers merge, the debris in the two lateral moraines merge to become a medial moraine

Question 32

Medial Moraine

Answer 32

often seen as a stripe running down the composite glacier

Question 33

End Moraine

Answer 33

The sediment that accumulates at the toe of the glacier (leading front edge).

Question 34

Terminal Moraine

Answer 34

the debris deposited by the furthest extent of glacial ice

Question 35

The Rocky Mountains

Answer 35

many of its peaks and valleys were glacially carved (from the midwest extending all the way to the west coast)

Question 36

The Great Lakes

Answer 36

the lakes occupy basins carved and deepened by glaciers and filled with glacial meltwater

Question 37

Canada’s Hudson Bay

Answer 37

is a depression formed by the weight of the ice sheets and flooded with seawater after the ice melted away

Question 38

The drainage of the Mississippi river

Answer 38

In part was formed by meltwater from retreating ice sheets. the sediments carried along with that meltwater are in part responsible for the fertility of the Midwestern farmland, and supply the groundwater tapped today for irrigation.

Question 39

How many ice ages have happened in the past billion years? Which was the most recent?

Answer 39

5 major ice ages in Earth’s history, the most recent took place during the Pleistocene Epoch

Question 40

Interglacial period

Answer 40

the time between when glaciers retreat and advance

Question 41

What geologic epoch are we in?

Answer 41

the Holocene, we are considered to be in an interglacial period because the glaciers are still present (though rapidly retreating)

Question 42

Milankovitch Cycles

Answer 42

looks at the change in the shape of the Earth’s orbit, tilt, and wobble of the Earth’s axis over time

Question 43

How is wind created?

Answer 43

Wind is created in response to differences in air pressure, which is related to air temperature. The surface of the Earth is heated more near the equator, less at the poles, causing the equatorial air to rise up into the atmosphere and move toward the poles, and the cooler polar air sink and move toward the equator, forming a series of convection cells.

Question 44

Where is wind erosion most effective?

Answer 44

In areas lacking vegetation, e.g., beaches, deserts. Strong winds can sandblast terrains and rocks creating ventifacts

Question 45

Ventifacts

Answer 45

stones with wind-abraded surfaces

Question 46

Deflation

Answer 46

removal of loose sediment by wind
This lowers the land surface via erosion, and can result in the loss of soil.

Question 47

Wind Deposition

Answer 47

this creates dunes, usually made of sand, but snow is also possible. The orientation of the dunes reflects the prevailing wind direction, which is the shallower slope side facing upward.

Question 48

Dune Migration

Answer 48

if there is a strong enough prevailing wind direction, a dune can migrate: its particles get blown up the side of one shallower surface and slide down the steep slip face.

Question 49

How do crossbeds develop in the dune?

Answer 49

slanted ones develop as layer upon layer of sediment slides down the slip face

Question 50

Where are deserts found?

Answer 50

deserts are found at all latitudes: the largest are subtropical but deserts can also be found at the poles.

Question 51

What are causes of natural deserts?

Answer 51

High surface temperatures and topography

Question 52

How does high surface temperatures cause a natural desert?

Answer 52

The sinking cool air at 30 degrees north and south of the equator results in desert environments due to the cooler air warming as it reaches the surface, taking with it much of the moisture, and causing rapid evaporation.

Question 53

How does topography cause a natural desert?

Answer 53

Mountain ranges that lie in the path of air currents may push the air to high altitudes as the air rises over the range, causing the air to cool and for it to lose its moisture. As a result, one side of the mountain range is extremely wet, but the opposite side is dry, as the now dry air forms a rain shadow.

Question 54

Rain Shadow

Answer 54

Moisture extracted on windward slopes of mountain ranges established by Topography and prevailing wind patterns

Question 55

Desertification

Answer 55

the rapid development of deserts is caused by the impact of human activities, usually as a consequence of land-use practices.

Question 56

Dust Bowl Desertification

Answer 56

in the 1930s the US Midwest as a result of decades of misguided farming practices caused the topsoil to erode away. Removing native vegetation and replacing them with crops leaves the land vulnerable to degradation during drier conditions.

Question 57

How does desertification impact food?

Answer 57

it reduces the amount of arable land on which the world depends for food.