Title: GLACIERS
1GLACIERS
2GLACIERS
- glaciology is the study of glacial activity
- Basic concepts
- Definition of glacier
- any moving mass of ice on Earth
- Classification of glaciers
- mountain(alpine) glaciers formed in and
restricted to the mountainous areas on Earth and
comprise a small amount of total glacial ice on
Earth - continental glaciersmassive ice on continents
comprising about 95 of total global ice
3GLACIERS
Changing of snow to ice
snow fall and accumulates and contains air
between flakes
as more snow accumulates, snowflakes farther down
are compressed forcing out a lot of the air
with increasing depth and pressure, snow
crystallizes to form ice, which can be considered
a rock
4GLACIERS
- Theories and concepts of all glacial ice growth
and demise - changes in temperature and/or precipitation over
a long time are the two most important conditions
governing the growth and demise of glacial ice - continental glaciers
- activity on sun solar flares and sun spots
- some believe a long term change in solar
intensity can cause a global temperature change
increasing or decreasing glaciers
5GLACIERS
- greenhouse effect
- Long term increases or decreases of carbon
dioxide in our atmosphere can increase or
decrease global temperatures to affect amounts of
global ice - increases of CO2 1) burning of fossil fuels 2)
volcanic activity--emissions of CO2 - decreases of CO2 1) chemical weathering of
extruded igneous rocks - plant use of CO2 for photosynthesis
6GLACIERS
- Donn-Ewing concept (not well accepted)
- land bridge across Bering Straits controls amount
of precipitation in the region by allowing
different temperature bodies of water (Arctic and
North Pacific Ocean) to mix when land bridge is
submerged ( increased precipitation)and not mix
when land bridge is exposed(decreased
precipitation) - this idea may explain the North American Ice
Age-- glacial ice in Greenland is a remnant of
that age
7Extent of global ice during North American Ice
Age
8GLACIERS
- atmospheric particulates
- volcanic activity on a large scale can cause
large amounts of particulates in the atmosphere
resulting in reflection of sun energy and cooler
global temperatures - plate tectonics and position of continents at
polar region and variation of Earths orbit - these 2, appear to be more popular
9GLACIERS
Position of plates before Continental Drift
10GLACIERS
Changes of Earths Orbital Variations
1. Tilt of Earths Axis of Rotation (takes about
40,000 years to cycle from minimum to maximum)
maximum tilt angle can lead to a decrease of
glacial activity because warmer summer
temperatures melt more south polar ice
minimum tilt angle can lead to an increase of
glacial activity because south polar area
receives less sunlight
present day tilt, adjusting back from last ice age
11GLACIERS
2. Shape of Earths Orbit (Eccentricitytakes
about 100,000 for cycle)
Eccentricity can cause a major climate change
12GLACIERS
3. Wobble of Rotation Axis (Precession)
Precession can cause global changes
13GLACIERS
http//highered.mcgraw-hill.com/sites/0073369365/s
tudent_view0/chapter16/milankovitch_cycles.html
14GLACIERS
each individual variation cannot explain glacial
activity, but by combining them as Milankovitch
did, appeared to show better resultsbut still
debated by some
MILANKOVITCH CYCLES
15GLACIERS
What about theories of growth and demise of
alpine glaciers ? growth and demise of alpine
glacial ice is more dependent on small term
changes as in seasonal temperature and
precipitation differences as is present in many
global mountainous regions. There can be alpine
glaciers active and caused by continental
glaciations
16GLACIERS
- Alpine and Continental Glacial Regiment
(movement) - growth and demise of glacial ice is based on rate
of accumulation versus the rate of
wastage(melting) for alpine and continental
glaciers
example of important alpine glacial areas
17GLACIERS
Photo of snowline and areas of accumulation and
wastage for an alpine glacier
18GLACIERS
- Alpine and Continental glacial flow at and below
ice surface--brittle zonecrevasses at surface
brittle-crevasse zone slower flow
mobile ice fastest flow
A lot of friction with rocksslowest flow
19GLACIERS
- Glacial deposits and erosion features
- all glacial deposits (Alpine and Continental) are
called drift - till is non-stratified drift and comprised of
non sorted or a mixture of different particle
sizes (see Wentworths scale)--deposited directly
by the glacial ice - outwash is stratified or layered drift with each
layer being well sorted--deposited directly by
glacial melt water
20Photo of till
21GLACIERS
Example of Non-Layered Till and Layered
Outwash
Sorted Outwash
Non-sorted Till
22GLACIERS
- Alpine glacial deposits and erosion features
- deposits--mostly till called moraine
- lateral moraine
- formed on sides of and present on surface of
glacial ice and results from the plucking and
pulverization of rock by the ice - medial moraine
- formed by convergence of 2 lateral moraines from
2 ice lobes
23GLACIERS
- end (terminal) moraine
- a ridge of deposit contouring the shape of front
of glacier formed from the discharged of
materials moved within the glacier like a
conveyor belt - represents the maximum advance position of the
glacier
24GLACIERS
lateral moraine formed on sides of glacier
medial moraine formed from 2 lateral moraines
from intersecting glaciers
terminal morainemost forward movement of glacier
25GLACIERS
- recessional moraine
- a deposit shaped similar to the end moraine
formed during a subsequent advancement of glacier
during its overall demise - many recessional moraines may occur during the
demise of a glacier - erosion features
- formed from the plucking nature of the glacier
26GLACIERS
- cirque
- semi-circular or amphitheater shaped--a tarn or
cirque lake can be present ---paternoster lakes
are a chain of interconnected tarns
2 cirques and tarns
27GLACIERS
- horn
- a peaked or pointed feature resulting from the
formation of a series of closely associated
cirques - best example is the Matterhorn
Matterhorn in the Alps
28GLACIERS
- arete
- a jagged or sawtooth ridge left between 2 glacial
lobes gouging rock material as they move to a
lower elevation
cirques and aretes
29GLACIERS
- U shaped valley
- is the typical shape of a valley carved by a
glacier - is best observed in the front profile view as you
look up the valley
30GLACIERS
- hanging valley
- formed from a glacial tributary lobe and hangs
over the main glacial valley - best example of this is Bridalveil Falls in
Yosemite National Park
31 Review of some alpine glacial depositional
and erosion features
GLACIERS
32GLACIERS
- Continental glaciers
- glacial ice in Antarctic and Greenland comprise
more than 90 of all glacial ice on Earth - if all the ice melted sea level would rise about
215 feet(195 feet from all ice associated with
Antarctic and 20 feet for that from Greenland)
33Glacial ice deposits on Antarctic and Greenland
34GLACIERS
Effects of continental glacial ice
formation or melting on sea level
35GLACIERS
- erosional features
- there are a few types of erosion features
associated with continental glaciers like the
Great Lakes and Driftless area in Wisconsin, but
the depositional features are more abundant - depositional features
- till
- ground moraine--an undulating massive blanket
like deposit formed on ground where glacial ice
was present
36GLACIERS
- end moraine--see alpine notes
- recessional moraine--see alpine notes
- drumlin--a streamlined symmetric inverted spoon
head shaped hill whose steep side faces the
direction from which the glacier
advanced---Bunker Hill in Boston is a drumlin and
is where a famous Revolutionary War battle was
fought
37GLACIERS
Field of drumlins in Baraboo, Wisconsin
38GLACIERS
Drumlinssteep side facing direction of
glaciers retreat
39GLACIERS
- Outwash (well sorted)
- outwash plain--a relatively flat massive blanket
like deposit consisting of layered and well
sorted particles deposited by glacial melt water
in the front and sides of the glacial ice - esker--a winding ridge comprised primarily of
sand and gravel layers deposited by a stream
flowing in a tunnel beneath a glacier near its
terminus
40GLACIERS
Esker
41GLACIERS
- kame--a steep sided hill comprised of sand and
gravel layers originating from the collection of
sediment in openings in stagnant ice - kettle
- hole or lake formed from a large melted block of
ice buried in the ground moraine or outwash plain
42GLACIERS
Review of some continental glacial
depositional features
43GLACIERS
drumlins
recessional moraines
esker
kettle lakes
terminal moraine