Geology Chapter 12 - Exam 3
we are currently in the interglacial period of warming that began about ______ years ago
10,000
antarctic glaciated more than __ million years ago
20
ice covered __% of the land surface of Earth and was _ km think in places
30, 4
____ million years ago there was glaciation in northern africa
500
initial snowpile is __% space
90
___ (or Valley) glaciers occur in valleys of mountainous regions
Alpine
____ ___ ____: type of glacier that flows freely and covers large expanses. Example: Antarctica and Greenland
Continental Ice Sheet
the last glacial maximum was during _____ about 180000 years ago
Pleistocene
shape of valley that glacier carves as it moves down the slope
U-Shaped Valley
zone of ____: where melting and calving occurs
ablation
if a crevasse is ____ 40 m in depth, ice is brittle and can crack
above
____ polishes underlying rock, grinds some into rock flour (fine grained material) and scratches bedrock making _____
abrasion, striation
zone of ____: where snow is added
accumulation
ridges separating glacial valleys
aretes
____ sliding and ____ flow: bottom of glacier slides on film of water and lower parts flow
basal sliding, plastic flow
if a crevasse is ____ 40 m in depth, ice is plastic and flows, it can't crack
below
streams that emerge from liquid water and glacial outwash are _____
braided
____: collapse of pieces of glaciers into the sea to from icebergs
calving
steep bowls carved by glaciers at their heads
cirques
_____: cracks that from in the rigid part of the glacier
crevasses
glaciers with sea ice form the ____sphere
cryosphere
moraine overridden by a glacier to make a hill
drumlin
___ moraines: ridges piled up at the front of the glacier
end
the _____ ____ separates zones of ablation and accumulation, and may change location from year to year
equilibrium line
sinuous ridge that forms beneath glacier as it recedes. type of outwash feature
esker
snow is then compacted and recrystallized into ___, which is well packed snow that survives summer melting
firn
____: sea level lower during glacial period, glaciers eroded onto continental shelf
fjords
coastal ____ are indirect effects of past glaciation
fjords
the difference between the annual gain and loss
glacial budget
____ ____: large boulder eroded from one type of bedrock and transported to another
glacial erratic
then the firn is turned into ____ ___
glacial ice
____ ____: sediment deposited by liquid water
glacial outwash
a large long-lasting mass of ice, formed on land that moved down hill under its own weight
glacier
___ ____: glaciers erode underlying rock by plucking of rock fragments and abrasion as fragments are dragged along
glacier erosion
___ ___: all glaciers move down slope in response to gravity regardless of whether they are receding or advancing
glacier flow
crevasses are rarely ____ than 40 m deep
greater
glaciers only form when snow accumulation is (greater than, less than) snow melting
greater than
the increases in atmospheric CO2 since the industrial revolution lead to the __________ effect
greenhouse
Erosion by one glacier and then a second can produce a "_____" valley
hanging
sharp peaks that from when cirques have formed on 3 sides of the mountain
horns
glaciers are part of the _____sphere, they tie up fresh water.
hydrosphere
most of Earth's fresh water is tied up in __ and about 70-75% of the total ____ water budget is in ice
ice, fresh
glacial lake
kettle
____ moraines: long, low mounds on sides of glaciers
lateral
___ ____: type of glacial deposition that flows over, beneath, and away from ice at glacier end
liquid water
glacial material can be transported far from its source and when it is deposited it is called ____
loess
___ sea levels causes canyons on continental shelf. indirect effect of past glaciation
lower
____ moraines: lateral moraines trapped between glaciers as they join
medial
accumulation of till on sides and fronts of glaciers
moraines
if the glacial budget is ____ it is shrinking and retreating
negative
there was ___ glaciation during the Mesozoic because it was a period of warming and movement of continents toward equatorial regions
no
greeland and antarctic ice sheets are _____
permanent
245-286 million years ago there was glaciation in australia, india, south america, and south africa. this is strong evidence for ____ ____ because at those times those continents sat on the south pole
plate tectonics
glacial erosion by ____ of rock fragments: water seeps into cracks, freezes, and mechanically breaks up the bedrock.
plucking
____ lakes are lakes that form during wet period and are indirect effects of past glaciation
pluvial
____ ___: humid, cool climate of glacial period yields more rainfall. Precipitation is greater than evaporation. form in landlocked basins,
pluvial lakes
glaciers are mostly limited to the ___ regions
polar
if the glacial budget is ____ it is growing and advancing
positive
_____ moraines: successive end moraines left by retreating glacier
recessional
in the ___ ___, the upper part of glacier goes along for the ride
rigid zone
the formation of glaciers begins with ____ and accumulation of ____
snow, snowflakes
the ___ pole was erected in 1956. the movement of the ice sheet has displaces it from current geographic pole several km away
south
_____ moraines: end moraine making farthest advance of glacier
terminal
type of glacial deposition that is unsorted and unlayered
till
____: ancient till deposits. the oldest is about 2.2 billion years old
tillite