Chapter 9: The Cryosphere
What factors could influence solar heating of Earth and glacial episodes?
-change in solar output (reflected in sunspot activity_ -increase in reflectivity (albedo) from snow or clouds causes cooling -release of greenhouse gases by volcanoes can trap more heat -volcanic ash and dust reflect solar radiation back into space, causing cooling
How snow and ice accumulate in glaciers
-snowflakes pressed together by weight of other snowflakes -more snow adds weight and compresses flakes into small spheres -increasing depth and pressure cause snow to become crystalline ice; commonly bluish from trapped air
Characteristics of a glacier
1. moving mass of ice, with rocks and finer sediment 2. cover broad areas or confined to valleys 3. Flow from higher elevations to lower ones 4. can merge becoming a wider, thicker glacier 5. forms depends on snowfall, temp., direction, and steepness of slopes
Since 1979 more than ___ of the polar ice cap has melted away
20%
What percent of Greenland and Antarctica includes Earth's glaciers?
95%
Accumulation of snow
> seasonal melt is main contributor to glaciers and ice caps
____ is covered by a vast, thick ice sheet, and sea ice forms a ring around it
Antarctica
The North Pole is within the deep ___ whig is mostly covered by sea ice
Arctic Ocean
Accumulation
The additions of mass of a glacier
Ablation
The loss of mass from a glacier
Interglacial period
a time in the past when both the climate and global ice cover were similar to those of today; ice sheets retreat, sea level rises
Lower Zone
ablation area; region of net loss where bare ice and old snow are exposed because the previous winter's snow cover has melted away
Upper zone
accumulation area, the part of glacier covered by remnants of the previous wirer's snowfall and is an area of net gain in mass
Earth's tilt: present day
adjusting back from maximum
Permafrost
characterizes periglacial regions; the active layer thaw in summer, becoming unstable, and refreezes in winter -when it melts, ground collapses
Kettle
closed basin
Ice cores
contain gas bubbles that give us samples of Earth's atmosphere to 100,000 years ago (records of climates)
Ice sheets
continent-size; cover nearly all the land within their margins
Earth's tilt: minimum
cooler summers, less melting, and more glaciers
Ice cap
cover mountain highlands or low lying land at high latitudes, flow radially out
Esker
curved ridge of sand and gravel
Outwash
debris reworked, transported and deposited by meltwater
Crevasse
deep, gaping fissure in the upper surface of a glacier
Terminus
end of the glacier; shifts in response to changes in the mass balance
Valley glacier
extends down-valley from a cirque
Sea Ice
forms by freezing of fresh water at the ocean surface, salt crystals are excluded
How do glaciers form?
from snow that accumulates and compacts until it is so dense that it is impenetrable to air (glacier ice=rock)
Pingoes
frost-heaved hills
Moraines
glacially bulldozed ridges of sediment
Fjord glacier
glacier in a marine coastal valley
Ice shelves
hundreds of meters thick occupy Antarctica's embayments
Patterned ground
ice-wedge polygons formed in the active layer as a result of cyclical freezing
Periglacial
land beyond the limit of glaciers and is mainly found i circumpolar regions
Gelifluction
mass wasting
Cirque glacier
occupies bowl-shaped depression
During glacial periods...
ocean becomes saltier
Cryosphere
part of Earth's surface that remains perennially frozen -sea ice -glaciers: 10% of earth's land surface -frozen ground: 20% of earth's land
Highly reflective surface (high albedo)
reflects sunlight back into spar, reducing surface air temperature
Drumlins
ridges of sediment or bedrock parallel to the direction of ice flow
During interglacials...
sea ice melts and ocean becomes less salty
Eccentricity
shape of orbit; influences global climate
A glaciers advance or retreat is the balance of the amount of ____.
snow and ice added and lost
Piedmont glacier
spreads out form a valley glacier onto a lowland
Equilibrium line
the boundary between the accumulation area and the ablation area -coincides with the local snow line
Snowline
the lower limit of perennial snow
Glaciation
the modification of the land surface by the action of glacier ice (also called ice age, glacial periods, and glacial stages)
Calving
the progressive breaking off of icebergs from the form of a glacier that terminates in deep water
Till
unsorted glacial debris deposited by ice
Earth's tilt: maximum
warmer summers near poles, more melting, and less glaciation
Glaciers
when snow and ice become so thick that gravity causes the frozen mass to move
Precession
wobble of rotation axis; influences global climate