Chapter 12-Glaciers

           Physical Geology Illustrated Vocabulary     
Cochise College                                                     
Geology Home Page  
Roger Weller, geology instructor
wellerr@cochise.edu  


glacial grooves, Yosemite Park, California
   

Chapter 12
copyright 2015-Roger Weller
last edited: 12/7/15

Special Links*
 Correlation between CO2 and temperature *
 All About Glaciers *

 

alpine glacier

-is a valley glacier.

 

Alps

-are a prominent mountain range in southern Europe.

 

arete

-is a skinny mountain ridge shaped on opposite sides by a series of glacial cirques.
-arete diagram

-arete-Mt.Whitney

 

avalanche

-is a large mass of snow that rapidly slides down a slope.

 

bergschrund

-is the large crack at the top of a valley glacier where it is pulling away from the mountain.
-bergschrund diagram

 

cirque

-is a scoop-like depression on the side of a mountain formed by a valley glacier eroding the
mountain.
-cirques, Kebler Pass, Colorado

-Rocky Mountains Park-cirque-1 

-Rocky Mountains Park-cirque-2 

           

continental glaciation

-occurs when glaciers cover a large portion of a continent.  Modern examples are Greenland and
the Antarctic.

 

crevasse

-is a very large crack on top of a glacier

 

crustal rebound

-During an ice age the weight of a thick continental glacier presses the crust of the earth down. 
After the glacier melts, the crust slowly rises up to its previous elevation.

 

drumlin

-is a long, skinny, cigar-shaped hill that has be sculpted by a glacier flowing over it.
-drumlin diagram

 

erratic

-is a boulder far removed from its original source and deposited by a glacier.

-Yosemite-glacial grooves and erratics-1           

-Yosemite-glacial grooves and erratics-3 

 

esker

-is a snakelike ridge of water lain gravel deposited by a steam flowing beneath a melting glacier.
-esker diagram
 

fiord

-is a U-shaped glacial valley that is partially flooded by seawater.
-fiord diagram
-fiord-Opal's Pals

 

firn

-is glacial ice, a granular form of ice similar to the material in a "slush ball".
-glacial ice-firn-Opal's Pals

 

frost wedging

-Water gets into a crack, freezes, and expands.  The tremendous pressures exerted by the
expansion of water into ice can cause the rock to split further.

 

glacial grooves

-As a glacier moves across bedrock, the large rocks that the glacier is dragging along gouge long
grooves.

-Yosemite-glacial grooves-1       

-Yosemite-glacial grooves-2     

 

glacial plucking

-is the process where glacial ice is frozen in cracks and as the glacier moves the ice pulls rock
fragments out of the bedrock.
-glacial plucking-Mt.Whitney

 

glacial polish

-A glacier moving across a bedrock surface can polish the bedrock by abrasion with the fine rock
material embedded in the ice.

-Yosemite-glacial polish 

-Mt. Whitney-glacial polish 
-Mt. Whitney-glacial polish-B

-Mt.Whitney-glacial polish-D

           

glacial striations

-are scratches left on boulders and cobbles and bedrock as rocks are dragged along by a glacier and rubbed
against each other during the movement.  Also includes large, long, linear features
-glacial striations-Mt. Whitney

-Montana- glacial striations*

 

glacial till

-is the unsorted rock debris, ranging from boulders to silt, that are left behind when a glacier melts.

 

glacier

-is a moving mass of ice on land that is at least 150 feet thick

 

hanging valley

-is a small U-shaped glacial valley exposed on the upper side of a larger U-shaped glacial valley. 
The smaller valley was formed in colder times by a tributary valley glacier meeting up with a
larger valley glacier.
-hanging valley diagram

 

horn

-is a mountain with very steep slopes which was carved with cirques on three or more by valley
glaciers.  The most famous glacial horn is the Matterhorn in Switzerland.

-Rocky Mountains Park-horn and cirques       

 

Ice Ages

-are distinct times in the history of the Earth when major portions of the continents were covered
by glaciers.

 

kettle

-is a small lake surrounded by glacial till.  A kettle is formed by a depression created by the
melting of a large piece of glacial ice covered over with till.
-kettle lake diagram

 

lateral moraines

-are the piles of glacial till deposited along the sides of a glacier.
-moraine diagram

 

loess

-is a very fine, silty material that started out as rock flour (rocks ground up by glacial action to a
fine powder), but is now a wind-deposited soil.

 

medial moraine

-When two valley glaciers merge to form a larger valley glacier, their area of contact is often
marked by a line of glacial debris accumulated from lateral moraines of the two glaciers.

 

outwash plains

-are flat land areas covered by the silty material carried by streams flowing away from a melting
glacier.

 

permafrost ground

-is semi permanent frozen ground.

 

rock flour

-is rock that has been crushed and ground to a fine powder by glacial action.

 

terminal moraine

-is the pile of glacial till at the base (snout) of a glacier.
-moraine diagram

 

U-shaped valley

-is created when a valley glacier scrapes out the bottom and sides of the valley that it is moving
through.
-U-shaped glacial valleys, Kebler Pass, Colorado

-Rocky Mountains Park-U shaped valley-1 

-Rocky Mountains Park-U shaped valley-2 

 

valley glacier

-is a glacier in a mountain valley.  A valley glacier is also known as an alpine glacier.

 

Wisconsin Ice Age

-is the most recent of the Pleistocene advances of glaciers moving across North America.  The
Wisconsin Ice Age ended about 15,000 years ago.

 

zone of ablation

-is the portion of a glacier below the snowline where the glacier is melting.

 

zone of accumulation

-is the region of a glacier above the snow line where ice in the form of snow is being added to the
glacier.

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