Module 8 Glaciers
Terms in this set (34)
Masses of ice that move over land. Also called rivers of ice.
Fastest glaciers move are 10 meters (30ft)
when glaciers form
when glaciers recede (melt)
Early Stages Glaciation Formation
Glaciers form in areas that
accumulate more snowfall than is lost
each year by melting (ablation). As
the snow accumulates over time, it
recrystallizes and changes to a
granular form. Recrystallized snow
left over from several seasons is
called firn. Firn is the intermediate
stage between snow and glacial ice.
Over a period of years, layers of firn
are compacted to form glacial ice that
then begins to flow under its own
recrystallied snow left over from several seasons. Intermediate stage between snow and glacial ice
Moving Forward Growth
At this point a glacier has begun to
move. It will move downhill by gravity
or outward in all directions if it is over
a flatter piece of land. Most glaciers
slide over a thin layer of water
underneath them. This water may
come from melting caused by
overlying pressure or by dripping
through cracks in the ice. This
movement of a glacier is called
Glacial Retreat Ablation
After some time in its journey, a
glacier may reach a point where
ablation exceeds ice accumulation.
At this point the glacier is said to be
in retreat. This photo shows how the
bottom boundary of a glacier
changed from 1985 to 2005 as it
underwent glacial retreat. At that
time, the glacier shrunk because
snow accumulation was slower than
loss by melting and ablation.
Parts of a Glacier: Head
The glacial head is the place where a glacier originates
Parts of a Glacier: Zones of Accumulation
The zone of accumulation is where there is a net gain of ice. This is the upper part of a glacier and the part that receives the most snow. Most of a glacier's area is in the zone of accumulation
Parts of a Glacier:Snowline
The snowline is the boundary between the zone of accumulation and the
zone of ablation. It is sometimes called the equilibrium line. Above this line,
snow accumulates; below it, there is a net loss of ice due to melting or
Parts of a Glacier: Crevasses
Crevasses are large cracks opened by the fracturing of upper ice layers.
The ice cracks when the bottom layers of ice flow but the top part remains
brittle. Crevasses may be thousands of meters long and as much as 30
Parts of a Glacier: Zone of Ablation
The zone of ablation may be the bottom of a mountain, the sea, or any
warmer environment. There is a net loss of ice, as ice leaves the system by
melting, breaking, or evaporation.
Parts of a Glacier: Terminus
The terminus is where a glacier ends.
Glaciers that originate on high mountain slopes
a special kind of alpine glacier that flows through a valley
a special kind of alpine glacier that forms in an amphitheatre-like bowl-shaped depression on the side of a mountain
a special kind of alpine glacier that emerges from the mountain front and spreads out as a large lobe at the foot of the mountain
a special kind of alpine glacier that terminates in the sea
The Antarctic Ice Sheet is the largest mass of ice on Earth. It holds more than 60% of all
freshwater on Earth, although it is all frozen. If the Antarctic Ice Sheet melted, global sea levels
would rise about 61 meters. Ice enters the sheet through precipitation as snow, which is then
compacted to form firn and then glacial ice. The ice then flows toward the coast, where it
eventually breaks apart to form icebergs that float in the sea.
How do alpine glaciers differ from continental ice sheets in terms of size and environment of formation?
Alpine glaciers form on high mountains, but continental ice sheets form in polar areas and over large
areas of relatively flat land. Alpine glaciers are smaller than continental ice sheets.
What are the distinguishing landscape features of the following: valley glacier, piedmont glacier, cirque
glacier, tidewater glacier?
Valley glaciers move through a mountain valley; they are bounded on both sides by high mountain
peaks. Piedmont glaciers are large lobes that have spread out over the land at the foot of a mountain.
Cirque glaciers form in bowl-shaped depressions on the sides of mountains. Tidewater glaciers terminate
at the edge of the sea.
Where are Earth's only continental ice sheets found? How do they flow and when do they make
Earth's only continental ice sheets are on Antarctica and Greenland. The glacier ice flows from the
interiors of the ice sheets towards the coastlines, where it eventually breaks apart to form icebergs that
float in the sea.
are scratches and gouges cut into bedrock by a glacier as it abrades the ground over which it flows. They usually occur as multiple, straight parallel grooves. They are carved out of rock by coarse gravel and boulders that are dragged along underneath a glacier.
are bowl-shaped basins carved out by a glacier. They form at the glacial head when a glacier erodes backwards, into the mountainside, forming a rounded hollow area.
are jagged, narrow ridges formed when two cirques meet, eroding the ridge on both sides.
such as the famous Matterhorn in Switzerland, are created when several cirque glaciers erode a mountain until all that is left is a steep, pointed peak with sharp, ridge-like aretes leading up to the top
are usually left behind after a glacier retreats. The glaciers scoop out the valleys, leaving steep sides and broad flat floors
such as those in Norway, are long, narrow coastal valleys that were originally carved out by glaciers. Steep sides and rounded bottoms give them a trough-like appearance. Because of glacial erosion on the land surface, which is below sea level, sea water covers the valley floor when glaciers finally disappear.
is any accumulation of glacial debris, such as soil and rocks, that has been dragged along by a glacier. The glacial debris that makes up a moraine is specifically called till. This glacial till may have been plucked off the valley floor as the glacier advanced, or it may have fallen off the valley walls as a result of weathering and erosion.
are long, winding ridges of sand and gravel. The sediments that make up eskers come from streams of liquid water that make their way through ice-walled tunnels and cracks in a glacier.
is an irregularly shaped hill or mound made of glacial till. It forms when a melting glacier makes a depression in the landscape, later leaving behind an assortment of sediments when it has completely melted.
are long, tear-shaped sedimentary landforms created when glaciers melt. They have a high, blunt end on one side, and a long, tapered end on the other side. The long, gently tapered end of a drumlin forms parallel to the direction of ice movement. The blunter and higher end (the end on the left in this picture) is the direction the glacier came from. The gentle slope (the right side in this picture) is the direction the glacier advanced.
are large pieces of rock carried by glacial ice, often for hundreds of kilometers, before being dropped or deposited.
are shallow sediment-filled bodies of water left behind by glacial meltwater