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
Slide 3
TYPES OF GLACIERS VALLEY GLACIERS Ice masses that slowly
advance down valleys that were originally occupied by streams A
stream of ice that flows btw steep rock walls from a place near the
top of the mountain valley ICE SHEETS Enormous ice masses that flow
in all directions from one or more centers and cover everything but
the highest land Covering Greenland & Antarctica Continental
Ice Sheets B/C they cover large regions where the climate is
extremely cold.
Slide 4
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
Slide 5
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
Slide 6
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.
Slide 7
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
Slide 8
LANDFORMS CREATED BY GLACIAL EROSION
Slide 9
Slide 10
7.2 DESERTS
Slide 11
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
Slide 12
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
