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Ch 13A
N/a
59
Geology
Undergraduate 1
04/22/2014

Additional Geology Flashcards

 


 

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Term
glacier
Definition
is a large mass of ice,
resting on land or floating in the sea:
– Cover ~11% of Earth’s land area today
Term
Two types
Definition
Alpine Glaciers
Continental Glaciers
Term
Alpine Glaciers
Definition
Glaciers in mountain ranges are termed
‘alpine glaciers’
Term
A valley glacier is confined within a valley:
Definition
– Range in length from 100m to over 100 km
– Erodes bedrock while flowing slowly downhill
– Transports and deposits debris
– A cirque is a bowl-shaped recess at the head
of the valley
Term
Continental Glaciers
Definition
A continental glacier is a continuous mass of
ice on continents
Term
A continental glacier is a continuous mass of
ice on continents
Definition
– Blankets 80% of Greenland and 90% of Antarctica
Term
Underlying crust is isostatically depressed
due to the enormous weight of the ice:
Definition
Crust depressed more than 2,000 m below sea
level in Greenland and Antarctica
Term
Continuous ice cover also associated with
mountains:
Definition
– Ice cap is roughly circular and covers less than
50,000 km2
– Ice field has elongated pattern with ridges and
peaks visible above the buried terrain
Term
Glacier is
Definition
an open system
Term
Glacier is an open system:
– Inputs:
Definition
Snow and other moisture
Term
Outputs
Definition
Ice, meltwater and water vapor
Term
On the lower end below the firn line, glacier is wasted
via ablation by several processes:
Definition
– Melting on the surface, internally and at the base
– Ice removal by deflation (wind)
– Calving of ice blocks
– Sublimation
Term
Equilibrium line
Definition
is where accumulation gain balances
ablation loss
Term
Rates of glacial flow ranges from almost
nothing to 1-2 km/yr:
Definition
– Depends on rate of snow accumulation
– Flowing glacier can develop crevasses
Term
Glacier can lurch forward in a surge
Definition
Possible cause is build-up of water pressure
underneath
Term
Passing glacier can pluck and remove
rock material via erosion:
Definition
Embedded rock can scour the landscape
through abrasion as the glacier moves
Term
Glacial erosion can convert
Definition
a V-shaped
stream valley into a U-shaped valley
Term
Two eroding cirques can create a
Definition
saddlelike
depression in between called a ‘col’
Term
A horn
Definition
results from several cirques
gouging a mountain summit from all sides
Term
Mountain lakes
Definition
Tarn
Paternoster lakes
Term
Tarn
Definition
small mountain lake
Term
Paternoster lakes
Definition
are a series of circular lakes
Term
fjord
Definition
forms when a glacial trough
intersects an ocean and seawater flows
inland
Term
Glacial drift consists of
Definition
unsorted and
sorted glacial deposits (rocks & sediment):
Term
Glacial drift consists of unsorted and
sorted glacial deposits (rocks & sediment):
Definition
Till
Stratified
Term
Till
Definition
unstratified (non-layered) and unsorted
Term
Stratified
Definition
(layered) drift deposited by glacial
meltwater
Term
Moraines
Definition
meltwater
Term
Moraines are specific landforms produced
by deposition of glacial sediment
Definition
Lateral moraine forms on either side of glacier
– Lateral moraines may merge to form medial
moraine
– Terminal moraine marks the glacier’s furthest
extent
Term
Continental glaciers form
Definition
across
broad, open landscapes
Term
Most erosional and depositional
features are
Definition
associated with glacial
retreat:
Term
Till plain forms
Definition
behind an end moraine
Term
Outwash plains of stratified drift
deposited by
Definition
glacial meltwater
Term
Other features associated with Continental
Glaciation:
Definition
Esker
Kettle:
Kame
Drumlin:
Term
Esker
Definition
Sinuous, narrow ridge of coarse sand and
gravel that formed by meltwater stream that
flowed beneath glacier
Term
Kettle:
Definition
Hole left behind after large block of ice
melts
Term
Kame
Definition
Small hill or knob of poorly-sorted sand
and gravel
Term
Drumlin:
Definition
Elongated deposit of till streamlined in
the direction of continental ice movement
Term
Periglacial Landscapes
Definition
Located in subarctic and polar climates
(tundra)
Term
Landscapes consists of frost weathering
and freeze-thaw shattering of rock:
Definition
Some associated with near-permanent ice
– Others at high elevation and seasonally snowfree
Term
Permafrost occurs when
Definition
soil or rock
remain below freezing for at least two years
but is not covered by glaciers
Term
The freezing of water in soil and rock
initiates frost action
Definition
– Expansion of water as it freezes fractures rock
and disrupts soil
Term
Saturated soil and rocks are subjected to
large displacements when freezing:
Definition
– Vertical movement called frost heaving
– Horizontal motions called frost thrusting
Term
Proper construction in
periglacial environments
requires
Definition
raising of buildings
and pipes above ground
Term
The Pleistocene Ice Age
Definition
The Last 1.6 Million Years
Term
During the early 20th century, four major
glacial advances were recognized and
mapped in North America:
Definition
Wisconsin (maximum ~18,000 years ago)
– Illinoian (ended ~130,000 years ago)
– Kansan
– Nebraskan (~2 m.
Term
Three to five were recognized in
Definition
EU
Term
Recent studies of deep-sea cores indicate
many
Definition
more glacial episodes than were
recognized on land
Term
Diverse Effects of Last Ice Age
Definition
Changes in oceanic circulation patterns
Term
Glaciers locked up abundant water on
continents, lowering sea level:
Definition
Coral reefs high and dry
– Continental shelves and land bridges exposed
– Rivers crossed exposed shelves, cutting canyons
– On land, downcutting by rivers formed terraces
Term
Sea Level Drop Lowered Base Level
Definition
Causing Streams
On Land To Downcut And Form Terraces
Term
Pleistocene Glaciation
(~18,000 years ago
Definition
• Several major ice centers
in Canada
• Low-stand of sea level
• Bering Land Bridge
Term
Isostasy
Definition
Following retreat of glaciers after the
last ice age, crustal rebound occurred
around Hudson Bay, Canada, and the
northern Baltic Sea over the last
10,000 years
Term
Lake Missoula Ice Dam
Definition
Ice dam first broke ~ 15,000 years ago
Term
Glacial Loess
Definition
Derived from outwash plains of glacial
meltwater
Term
Derived from outwash plains of glacial
meltwater
Definition
– Meltwater carried large volumes of sediments from
melting ice sheets; sediments deposited in
outwash plain
Term
During the fall and winter, melting of ice
sheets ceased
Definition
– Flow of meltwater either ceased or was greatly
reduced
– Unvegetated floodplains dried out and were
exposed to the wind
– Glacially ground flour-like silt and clay winnowed
by the wind
– Particles blown downwind and deposited as loess
deposits
Term
Western U.S. was dotted with large
lakes 12,000 – 30,000 years ago:
Definition
A time of wetter conditions during
glaciation
Term
Definition
Lacustrine Deposits: Lake sediment that
form terraces along former shorelines
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