Virtual Exploration #2
How do Glaciers Move? 


This image was taken by Matthew Durant 
at the Northwestern Glacier.

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 Questions

How do Glaciers Move? 

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I want to embark on Virtual Exploration #2

 

 

 

   Virtual 
 Exploration

Virtual Exploration #2
How do Glaciers Move?

This image was taken by Matthew Durant 
at the Northwestern Glacier.

Many people refer to glaciers as "Rivers of Ice".  It's not a bad metaphor because glaciers actually do slowly move.  In South Central Alaska, the snow piles up fast.  Most years, this part of Alaska gets over 700 inches.  All the snow begins to add pressure to the snow below and it slowly transforms it into firn and then glacial ice.  Finally, the pressure builds so high that it squeezes glacier ice over the sides and the glacier moves slowly downhill.

 

	Harding Ice Field Way up here on the Harding Ice Field, the snow accumulates and metamorphoses into moving glacial ice.   Here on the Harding Ice Field, we are about one mile high on top of the Chugach Mountains.   We cannot even see the other side of the Ice Field because it covers nearly 700 square miles.  The ice here is amazingly thick.  Scientists think that the ice is thousands of feet deep. As you look around, it dawns on you that you can see forever over these flat ice fields.  There are only a few hills which your computer tells you are actually the tops of several mountains that are sticking up above the glacial ice.  The Alaskan Natives called these granite mountain tops, Nunataks, which means "lonely peaks".
	Glaciers Begin To Move Near the edge of the ice field you can see where the pressure has pushed the glacial ice over the edge.  You are seeing the beginning point of the Northwestern Glacier as it starts flowing down towards the Pacific Ocean.  Your computer tells you that the Northwestern Glacier is one of thirteen named glaciers and a host of other unnamed glaciers that flow from the Harding Ice Field.
	Glaciers that Move  Listen to that Glacier!!!  Do you hear those creaks, groans, scrapings, and booms?  That's what a glacier sounds like when it moves.  I know you can't see it moving because it is moving so slowly but it is.   A glacier moves forward (advances) when there is a lot of snow falling up in the ice field.  That new snow adds pressure to the snow, firn and glacier ice below.  The pressure builds and builds until it squeezes the glacier ice over the side of the ice field and it starts flowing downhill.  In the Winter when it is really cold and the glacier gets a lot of snow, it will advance.
	Regelation When glaciers are moving slowly downhill, they may be forced to move one way or another to go around a valley wall.  Other times a glacier will move around smaller objects that are in the way. When a glacier flows into an object in its way, the uphill side of the glacier continues to press downward, making it come under extreme pressure.  That causes a thin layer of the glacier ice to melt.  A super thin layer of water flows around the small object and freezes on the downhill side.  By transferring ice in this manner, glaciers can move slowly around small objects.
	"Warm Glaciers" Look over there.  See that river flowing from below the glacier.  That river is made up of melt water, water from the glacier melting.  Sometimes, glaciers move when a thin layer of this melt water gets trapped between the glacier and the bedrock.  This trapped melt water provides lubrication for the massive glacier above to flow over the bedrock below.  As the glacier moves, it generates lots of friction, which creates more heat, leading to more water below, which make the glacier move more.
	Crevasses As the glacier flows over a steep drop, the strength of the ice is stretched to its maximum limit and it breaks apart.  This results in crevasses.  You would not want to hike across that crevasse area.  Some of those crevasses are hundreds of feet deep.
	Calving  When it is warmer and sunny, the glacier melts enough so that it recedes or shrinks.  Our fellow scientists call this ablation.  Remember, at the Northwestern Glacier when that huge chunk of ice calved into the ocean?  That was one sign of ablation.   Remember, the river flowing from Exit Glacier on that warm sunny day last July?  That was another sign of ablation.  Over the course of the year the glacier will move forward and ablate.
	Measuring Glacial Movement Your fellow scientists have been using a Doppler Laser to measure the amount of glacial movement at Exit Glacier and other Alaskan glaciers.   In less than a minute, they can determine minute distance changes as little as .000001 inches per second.  When researchers have compared their Doppler Laser findings of Exit Glacier to measurements taken in the 1950's, they found that the glacier has thinned and retreated by about 150 feet.    Many other glaciers are showing ablation as well.  Glaciers have been shrinking all over the state.  But, why?  Global Warming?

   Online 
 Resources

Mass Balance Animation	A great Quicktime simulation of how glaciers move.
How glaciers move	Lots of writing but great information with super images.
Animation of Glacier Retreating	A great animation of a glacier receding.
Video of Glacier Calving	A Quicktime video of a glacier calving.
Alaskan glaciers melting faster	Scientists finding proof about what everyone already knows:  Alaskan glaciers are melting.

 

   Further 
 Reading

Alaska's Glaciers. Alaska Geographic volume 9, number 1, 1982.

An observer's guide to the glaciers of Prince William Sound, Alaska. Valdez, AK:  Prince William Sound Books,  1987. 

Glacier. R. H. Bailey and the Editors of Time-Life Books Alexandria, VA: Time-Life Books, 1982.

Glaciers  John Gordon.  Stillwater, MN Voyageur Press, 2001.

Glaciers, Natures Frozen Rivers. H. H. Nixon and J. L. Nixon. New York: Dodd, Mead, 1980.

Glaciers of North America: A Field Guide. S. A. Ferguson. Golden, CO: Fulcrum Press, 1992.

Blue Ice in Motion: The Story of Alaska's Glaciers  S. Wiley. Alaska Natural History Assn. 1995.

   Hands-On
 Activity

Regelation of Glaciers

1. Discussion: What do you know about how glaciers move?
   
   

2. Place your model glacier from your last activity onto a cookie cooling rack.  Place the board and rocks back on top of the glacier to simulate the pressure that glaciers get from the massive amounts of snow above.  Place the whole thing back into the freezer.
   
   

3. Hypothesis:  What do you think is going to happen to your model glacier?
   
   

4. Observe your glacier once each week for one month.  Take notes and make a sketch in your science journal of any changes that take place.

Make a PowerPoint Presentation to show evidence that  glaciers move.

1. Discussion: What do you know about how glaciers move?
   
   

2. Create a PowerPoint Presentation to teach others about how glaciers move.
   

   1. Gather images that show evidence of glacier moving, using this website and other web sites (see online resources).
      

   2. Use Google Image Search to look for evidence of glacier movement on these major Alaskan glaciers:
      (Exit Glacier, Hubbard Glacier, Berring Glacier, Northwestern Glacier, Portage Glacier, Columbia Glacier, Worthington Glacier, Kennicott Glacier, Meares glacier, Talkeetna Glacier, Matanuska Glacier, Mandhall Glacier)
      

   3. Remember to ask for and receive permission before you use images you get from the Internet. 
      

   4. Place your images into a PowerPoint Presentation.  PowerPoint is a great tool to show people what you are talking about.  Use lots of images with a few key words.
      

   5. Share your PowerPoint Presentation with your friends.
      

   6. E-mail your PowerPoint Presentation to (powerpoint@iwebquest.com) and we'll put it up on the Internet to share with the other scientists on our team.

 Assessment Guide

Click here to see a rubric to help you assess and revise your own work.

 

 Revisit the Question

How do Glaciers Move? 

 

Home    What is a Glacier?    How do Glaciers Form?  
How do Glaciers Move?    How do Glaciers Shape the Land?

 

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