Re: What tools do scientist use to measure the movement of glaciers?

Neena,

Several tools may be used.  The simplest, and the original tools used were 
simple surveying instruments like transits.  A fixed reference position was 
established on bedrock near the glacier and a line of stakes was hammerred 
into the ice.  The positions of the stakes were surveyed very accurately and 
then scientists would return after a few months or after a year, find the 
reference mark and then repeat the survey.  This technique is still 
occasionally used, however today's scientist is likely to use a Global 
Positioning System satellite receiver to find the position of her markers.

For larger-scale studies or for areas so remote they cannot easily be 
reached by scientists, a new technology is now proving itself.  Sidelooking-
airborne radar (SAR) can be used to compute glacial movement by comparing 
images taken a few hours or days apart.  The process of comparing the two 
sets of radar data is called interferometry because the motion data comes 
out of the interference patterns generated when two sets of waves interact 
with each other.  The math involved is intense and this technique is only 
possible with the assistance of powerful computers (no human could do the 
calculations in a reasonable amount of time).  One example from a Canadian 
study  is shown on this website:
 http://www.ccrs.nrcan.gc.ca/ccrs/tekrd/radarsat/images/ant/rant01e.html

SAR interferometry is currently being used to study the motion of the 
Anarctic ice sheets, which are the biggest glaciers in the world.  SAR is 
carried in planes on satellites and on the Space Shuttle.  It has also been 
used to map the motion of the ground associated with earthquakes and 
volcanic eruptions.

Both of the previous techniques only measure the motion of the top of a 
glacier Scientists who are interested in the motion of the insides need to 
do things like drill holes into the ice, wait a while (weeks, months, a 
year...) and come back with instruments that can map the tilt of a bore hole 
and check to see how the hole has deformed.  If different layers move with 
different speed, the hole will get tilted by an amount that depoends on the 
relative motion.

I'm glad you are interested in this.  Glaciers hold much important 
information about the earth's recent history.  Search the web and your local 
library under Glacier and Glaciology (the study of glaciers) for more 
information.

I grew up not far from you (Webster, NY) so I know that you can see 
lots of good glacial geology right around your home, or go to Mendon Ponds 
Park, in Monroe County, south of Rochester for a day once the snow melts.  
They have a great glacier interpretive trail and drive.  Here's the park 
website:
 http://www.co.monroe.ny.us/parks/mendonponds.html

Enjoy!  (I started studying geology when I was your age.  Every scientist 
knows, but most teachers don't, that science is a lot of fun along with a 
lot of work.  Don't ever let anyone convince you otherwise and you could be 
leading a research team on a glacier yourself, someday.)

David Smith, Ph.D.
Dept of Geology and Environmental Science, La Salle Univ., Philadelphia, PA