Chapter 9: The Cryosphere

Question 1

Define ‘Ablation’.

Answer 1

The loss of mass from a glacier.

Question 2

Define ‘Accumulation’.

Answer 2

The additions of mass of a glaciers.

Question 3

Define ‘Bed’.

Answer 3

The smallest formal unit of a body of sediment or sedimentary rock.

Question 4

Define ‘Calving’.

Answer 4

The progressive breaking off of icebergs from a glacier that terminates in deep water.
Recession of coastal glaciers is characterized by calving,

Question 5

Define ‘Cirque’.

Answer 5

A bowl-shaped hollow on a mountainside, open downstream, bounded upstream by a steep slope (headwall), and excavated mainly by frost wedging and by glacial abrasion and plucking.

Question 6

Define ‘Crevasse’.

Answer 6

A deep, gaping fissure in the upper surface of a glacier.

Question 7

Define ‘Cryosphere’.

Answer 7

The part of the Earth’s surface that remains perennially frozen.

Question 8

Define ‘Equilibrium line’.

Answer 8

A line that marks the level on a glacier where net mass loss equals net gain.

Question 9

Define ‘Fjord’.

Answer 9

A deep, glacially carved valley submerged by the sea. Also spelled fiord.

Question 10

Define ‘Glaciation’.

Answer 10

The modification of the land surface by the action of glacier ice.

Question 11

Define ‘Glacier’.

Answer 11

A permanent body of ice, consisting largely of recrystallized snow, that shows evidence of downslope or outward movement, due to the stress of its own weight.
Important glacier types include cirque glaciers, valley glaciers, ice caps, fjord glaciers, and piedmont glaciers.

Question 12

Define ‘Glacier ice’.

Answer 12

Snow that gradually becomes denser and denser until it is no longer permeable to air.

Question 13

Define ‘Ice’.

Answer 13

The solid form of H2O.

Question 14

Define ‘Ice cap’.

Answer 14

A mass of ice that covers mountain highlands, or low-lying lands in high latitudes.

Question 15

Define ‘Ice sheet’.

Answer 15

Continent-sized mass of ice that covers nearly all the land surface within its margins.

Question 16

Define ‘Ice shelf’.

Answer 16

Floating sheets of ice, hundreds of meters thick, that occupy large embayments along the coast of Antarctica.

Question 17

Define ‘Interglacial period’.

Answer 17

A time in the past when both the climate and global ice cover were similar to those of today.

Question 18

Define ‘Loess’.

Answer 18

Wind-deposited silt, sometimes accompanied by some clay and fine sand.

Question 19

Define ‘Moraine’.

Answer 19

An accumulation of drift deposited beneath or at the margin of a glacier and having a surface form that is unrelated to the underlying bedrock.

Question 20

Define ‘Periglacial’.

Answer 20

A land area beyond the limit of glaciers where low temperature and frost action are important factors in determining landscape characteristics.
The most characteristic feature of periglacial regions is permafrost.

Question 21

Define ‘Permafrost’.

Answer 21

Sediment, soil, or bedrock that remains continuously at a temperature below 0°C for an extended time.

Question 22

Define ‘Polar glacier’.

Answer 22

A glacier of high altitude or high latitude within which the temperature remains below the pressure melting point (little or no seasonal melting).

Question 23

Define ‘Sea ice’.

Answer 23

A thin veneer of ice on polar oceans that covers approximately two-thirds of the area of Earth’s persistent ice cover.

Question 24

Define ‘Snow’.

Answer 24

Precipitation that consists of solid H2O in crystalline form.
Snow forms as a result of the crystallization of tiny water droplets into feathery ice crystals in clouds, at very low temperatures. The crystal structure of snow is open and porous, but when deposited as precipitation it settles and becomes compacted. Snow that accumulates from one season to the next becomes more compacted, and the feathery snow recrystallizes into a denser texture characteristic of glacier ice.

Question 25

Define ‘Snowline’.

Answer 25

The lower limit of perennial snow.

Question 26

Define ‘Surge’.

Answer 26

An unusually rapid movement of a glacier marked by dramatic changes in glacier flow and form.
In most glaciers, flow velocities range from a few centimeters to a few meters a day but glacial surges, up to 100 times faster, may be facilitated by water trapped at the base.

Question 27

Define ‘Temperate (warm) glacier’.

Answer 27

A glacier in which the ice is at the pressure-melting point and water and ice coexist in equilibrium (low and middle latitudes).

Question 28

Define ‘Terminus’.

Answer 28

The outer, lower margin of a glacier.

Question 29

Define ‘Till’.

Answer 29

Unsorted sediment deposited by a glacier.

Question 30

In the northern hemisphere, much of the ice floats as a thin layer on the ___ Ocean; in the southern hemisphere, it is dominated by a vast ice sheet covering the continent of ___ and adjacent islands and seas. The cryosphere also includes large areas of permafrost, as well as seasonal snow cover, and glaciers in alpine areas.

Answer 30

Arctic and Antarctica.

Question 31

In the northern hemisphere, almost ___-___ of the land area is covered by seasonal snow and frozen ground during the winter.

Answer 31

One-quarter.

Question 32

The altitude and position of the snowline change from year to year, controlled by ___ and ___.

Answer 32

Temperature and precipitation.

Question 33

The huge continental ice sheets of Greenland and Antarctica contain about __ percent of existing glacial ice.

Answer 33

95%.

Question 34

Floating ice shelves occupy large embayments along the coasts of ___ and among the ___ islands.

Answer 34

Antarctica and Arctic.

Question 35

Glaciers occur at sea level in the ___ regions and above the snow line in high mountains near the ___. Low temperature and proximity to a moisture source are requirements for glacier formation. The existence of glaciers thus depends on ___ forces to produce high mountains, the ___ to provide moisture, and the ___ to deliver the moisture to the land as snow.

Answer 35

Polar and equator.

Tectonic, ocean, and atmosphere.

Question 36

The mass balance of a glacier depends on the balance between ___ and ___. When a glacier gains more mass than it loses over a period of years, its volume ___ and the terminus ___. A succession of years in which negative mass balance predominates will lead to ___ of the terminus.

Answer 36

Accumulation and ablation.
Increases and advances.
Retreat.

Question 37

A ___ ___ occurs between a climatic change and the response of the glacier terminus because it takes time for the effects of changes above the equilibrium line to be transferred through the slowly moving ice to the terminus.

Answer 37

Time lag.

Question 38

Describe internal flow.

Answer 38

Deep within a glacier, individual ice crystals are subjected to stress from the weight of overlying snow and ice. Their internal crystal planes become aligned, facilitating deformation and flow. In contrast, the surface portion of a glacier is brittle; if it passes over an abrupt change in slope, it will develop deep crevasses.

Question 39

Describe basal sliding.

Answer 39

Meltwater at the base of a glacier acts as a lubricant, leading to basal sliding along the bed.

Question 40

Icebergs float with most of their volume…?

Answer 40

Below sea level.

Question 41

Glaciations have been prevalent during the Pleistocene Epoch, but there is evidence of glacial–interglacial cycles as long ago as ___ billion years.

Answer 41

2.4.

Question 42

During the most recent ice age, early humans migrated into North America from Asia across a land “bridge” that was exposed because such a large volume of water was locked up in glacial ice, causing sea levels to ___.

Answer 42

Decline.

Question 43

The ice sheets of the most recent glaciation reached their maximum extent about ___ years ago; by ___ years ago Earth had emerged from the ice age and entered the present interglacial period.

Answer 43

24,000 years ago.

10,000 years ago.

Question 44

As a medium for transporting sediment, ice can transport large and small pieces side by side without sorting them by size and density. The load of a glacier typically is concentrated at its ___ and ___, where glacier and bedrock are in contact. A significant component of the basal load of a glacier consists of very fine rock flour.

Answer 44

Base and sides.

Question 45

Small rock fragments embedded in ___ ice produce long, parallel striations and grooves, aligned in the direction of ice flow. In mountainous regions, ___ are produced by frost-wedging, combined with plucking and abrasion at the glacier bed. A valley that has been shaped by glaciers has a distinctive ___-___ cross section and a floor that lies below its tributary valleys. Smooth, parallel, streamlined ___ are elongated parallel to the direction of ice flow.

Answer 45

Basal.
Cirques.
U-shaped.
Drumlins.

Question 46

Some glacial landforms are produced by the deposition of rock debris eroded by the glacier or dropped onto the glacier’s surface from adjacent cliffs. ___ is a glacial sediment that occurs in unsorted and unstratified deposits. Debris that reaches the margins or terminus of the glacier may be redistributed by meltwater and deposited as ___. ___deposits form along the edges or terminus of a glacier, or where two glaciers merge.

Answer 46

Till.
Outwash.
Moraine.

Question 47

The largest areas of permafrost occur in northern ___ ___, northern ___, and the ___ ___. Most of today’s permafrost is believed to have originated during the last glacial age or earlier glacial ages. Instability due to seasonal thawing of the active layer can make it challenging to live with permafrost.

Answer 47

North America, northern Asia, and the Tibetan Plateau.

Question 48

Landscapes in periglacial regions reflect the movement of regolith in the active layer during annual freeze/thaw cycles. Describe some examples.

Answer 48

• Patterned ground and pingoes form as a result of cyclical freezing and thawing in the active layer.
• Solifluction is a common mass-wasting process in which waterlogged regolith in a thawed active layer moves slowly downslope.
• Periglacial regions are often associated with thick deposits of fine-grained, buff-colored loess, an aeolian sediment derived from rock flour.

Question 49

Glacial ice contains abundant physical, chemical, and biological evidence of past changes in local and global environmental conditions. Describe some characteristics that scientists have investigated.

Answer 49

The retrieval of deep-ice cores for both polar and alpine glaciers has allowed atmospheric scientists to determine how the concentrations of atmospheric greenhouse gases have fluctuated as the climate changes. The chemistry of the ice itself can reveal the air temperature when the snow first accumulated. Ice cores also provide a record of major volcanic eruptions, dustfalls, and other evidence of changes in atmosphere and climate.

Question 50

Approximately two-thirds of Earth’s permanent ice cover is sea ice. How does sea ice form?

Answer 50

The formation of sea ice has an important influence on the salinity of ocean water because salt is excluded from ice crystals as they form. Once the ocean surface cools to the freezing point of seawater, slight additional cooling leads to ice formation. It first forms small platelets and needles of frazil ice, eventually developing pancake-like masses that merge into a continuous sheet. Subsequent growth occurs by the addition of ice to the base.

Question 51

The open Southern Ocean surrounding Antarctica contrasts with the largely land- locked Arctic Ocean. How do these differences affect ice distribution?

Answer 51

In the Antarctic region, sea ice forms a broad ring around the continent, which varies seasonally; in contrast, the Arctic Ocean is ice-covered most of the year. Perennial ice zones contain sea ice that persists for at least several years; in seasonal ice zones, the ice cover varies annually.

Question 52

Sea ice is in constant motion, driven by winds and currents. Stresses resulting from movement cause the ice to break, exposing the underlying water. A linear opening, or ___, may grow to become a large area of open water, or ___. Because of the large temperature gradient between the air and seawater in a polynya, the water loses heat rapidly, causing a new, thin cover of ice to form. A fractured ice pack is thus a complex mosaic of new ice and older ice.

Answer 52

Lead.

Polynya.

Question 53

The ___ and ___, and therefore the global circulation of the world ocean, are directly influenced by the formation and melting of ice.

Answer 53

Salinity and temperature.

Question 54

How does the albedo of ice affect polar regions?

Answer 54

Ice has a high albedo, which makes the ice-covered polar regions far colder than if the same areas were covered with water or land.

Question 55

Would melting sea ice or land ice have a greater impact on sea level?

Answer 55

In a warming climate, the melting of sea ice would have much less impact on sea level than the melting of land ice.