Transcript Visualizing Earth Science

GLACIERS AND CLIMATE
CHANGE
Objectives
• Distinguish between several different kinds of glaciers
and ice formations.
• Describe how ice in a glacier changes form,
accumulates, ablates, and moves.
• Explain how geologists learn about past climatic
conditions.
• Examine evidence for anthropogenic climate change.
Glaciers and Ice Sheets
• Cryosphere
– The perennially frozen part of the
hydrosphere
• Components of the cryosphere
– Glaciers
• A semi-permanent or perennially
frozen body of ice,
• Consists largely of re-crystallized
snow
• Moves under the pull of gravity
– Temperate glaciers
– Polar glacier
– Ice sheets
– Ice shelves, ice bergs
Glaciers and Ice Sheets
• Components of the cryosphere
– Glaciers types
• Temperate glaciers
– Ice is near melting point throughout the interior
– Dominated by meltwater
– Form in low and middle latitudes
• Polar glacier
– Little melting occurs (cold temperatures)
– Form in high latitude or altitude regions
Glaciers and Ice Sheets
• Components of the cryosphere
– Glaciers types
Glaciers and Ice Sheets
Glaciers and Ice Sheets
Glaciers and Ice Sheets
• How glaciers form
– Snow that survives for more than a year gradually becomes
denser until it is no longer penetrable by air and becomes
glacier ice.
– Further changes happen as the glacial ice is buried deeper
(increasing pressure)
Glaciers and Ice Sheets
• How glaciers grow and shrink
– A glacier is measured using the amount of snow
(winter) and the amount of melting (summer).
– The difference between accumulation and ablation is a
measure of the glacier’s mass balance
Glaciers and Ice Sheets
Glaciers and Ice Sheets
• How glaciers move
– Glaciers move because
of the pull of gravity
– Ice in the central part of
the glacier moves faster
then the sides, and the
uppermost moves faster
than the lower layers
Glaciers and Ice Sheets
Glaciers and Ice Sheets
• Internal flow
– Ice moves in a glacier
through a combination
of ductile deformation
at depth and brittle
deformation at the
surface
– Crevasse
• A deep gaping fissure in
the upper surface of a
glacier
Glaciers and Ice Sheets
• Basal sliding
– Ice at the bottom of a
glacier slides across its
bed (the rock or sediment
which the glacier rests
on)
– The glacial landscape
• Glacier acts like a file,
sled, and plow
Glaciers and Ice Sheets
Glaciers and Ice Sheets
• Glacial erosion
– Glacial striations
– Glacial grooves
– Cirques
Glaciers and Ice Sheets
• Glacial deposition
– Till
• A mixture of crushed rock,
sand, pebbles, cobbles, and
boulders deposited by a
glacier
– Moraine
• A ridge or pile of debris that
has been, or is being,
transported by a glacier
Glaciers and Ice Sheets
Glaciers and Ice Sheets
• Periglacial landforms
– Tundra
– Permafrost
• Ground that is
perennially below the
freezing point of
water
– Ice wedges
– Patterned ground
• Produced by freezethaw cycle
Global Climate Change
• Global warming
– A profound change in the worlds climate
• Climate change in the past
– Glaciation
• A period when global temperature drops by several degrees,
• Expansion of continental ice sheets
Global Climate Change
Global Climate Change
Global Climate Change
• Study of past climates
– Paleoclimatology
• Causes of climate
change
– Geographic changes
resulting from tectonism
– Astronomical factors
– Green house effect
Global Climate Change
Global Climate Change
• Present day changes
– What we know
• Anthropogenic
– Produced by human activities
Global Climate Change
• Present day changes
– What we think
• General circulation models allow us to estimate impact of burning
fossil fuels or make projections
Global Climate Change
Global Climate Change
Critical Thinking
• How can you tell the age of the “fossil air” inside an
ice core?
• Can you think of any other natural environments that
have hexagonal patterns similar to patterned ground
associated with periglacial landforms?
• Does you city, state, province, or country have goals
for the reduction of carbon dioxide emissions to limit
its contribution to global warming?