TYPES OF GLACIERS
• Glacier – thick ice mass that forms over hundreds or
thousands of years.
• 15, 000 years ago > 30 % coverage - Today 10 % coverage
• Valley Glaciers
• Ice Sheets
TYPES OF GLACIERS
VALLEY GLACIERS
ICE SHEETS
• Ice masses that slowly
advance down valleys
that were originally
occupied by streams
• Enormous ice masses
that flow in all directions
from one or more centers
and cover everything but
the highest land
• A stream of ice that
flows btw steep rock
walls from a place
near the top of the
mountain valley
• Covering Greenland &
Antarctica
• Continental Ice Sheets
• B/C they cover large regions
where the climate is extremely
cold.
HOW DO GLACIERS MOVE?
• Movement of glaciers = flow
• Glacier flow happens 2 ways
• Plastic Flow
- Movement within the ice
- Under high pressure > begins to distort & change
shape (Plasticity)
• Basal Slip
- Gravity causes the entire ice mass to actually slip
and slide downhill
- Crevasses = gaping cracks up to 50 m deep
HOW GLACIERS MOVE?
• Budget of a Glacier
• The balance of lack of balance btw accumulation at the
upper end of the glacier and loss, or wastage, at the lower
end
• Form where more snow falls in winter than can melt during
summer
• Gain & loose ice
• Snow accumulates > ice forms in the head of the glacier in
the zone of accumulation
• Area of the glacier beyond the snowline = zone of wastage
• Rates of Glacial Movement
• Different glaciers = different speeds
GLACIAL EROSION
• Plucking
• Melted water from a glacier refreezes around lumps of broken
up rock. The ice then moves downhill and the rock is plucked
from the back wall.
• Abrasion
• Glacial ice & its load of rock fragments slide over bedrock,
they work like sandpaper to smooth out the surface they are
moving over.
GLACIAL EROSION
• Rate of glacial erosion is determined by
•
•
•
•
Rate of Glacial Movement
Thickness of Ice
Shape, abundance, & hardness of the
rock fragments in the ice at the base
Type of surface under the glacier
LANDFORMS CREATED BY GLACIAL EROSION
GEOLOGIC PROCESSES IN ARID CLIMATES
•
Weathering
• Most of the weathered debris in the deserts have resulted from mechanical
weathering
• Chemical weathering is not totally absent in deserts. Over time clays and thin
soils do form
•
The Role of Water
• In the desert, most streams are ephemeral (the only carry water after it rains)
• Dangerous flash flooding
• Lack of vegetation allows water to run off the land even faster
BASIN AND RANGE: A DESERT LANDSCAPE
•
Playa lake was a basin floor originally before abundant rainfall or snowmelt
•
Playa lakes only last a few days or weeks before they are evaporated and
infiltrated
•
Most of the streams in the desert dry up before they reach the ocean
•
Most of the desert erosion occurs due to running water
•
Wind erosion is more significant in deserts than elsewhere, BUT water does most
of the erosion in the desert