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