Alaska Glaciers
Tongass National Forest, Tracy Arm, Sawyer Glacier (Alaska). Photo by Gerald and Buff Corsi © California Academy of Sciences.
DB: This is Earth and Sky with a question from a listener in Sitka, Alaska. He writes, “Are the glaciers we see here in Alaska remnants of the last ice age – or newer, more recent formations?”
JB: The geologists we talked with said that some Alaskan glaciers are very dynamic. For example, the glaciers of southeastern Alaska receive large amounts of snowfall each year. These glaciers give rise to a lot of melting, and – if they reach the sea – they might spawn icebergs. Snow that fell on a glacier in southeastern Alaska a few hundred years ago might have melted already – or it might be calving from the glacier as a new iceberg this year.
DB: But ice in different parts of a glacier moves at different speeds. Ice near the surface moves relatively quickly – at around 60 meters, or about 200 feet, each year. The ice near most glaciers’ surfaces may be no more than about 500 to 1,000 years old.
JB: On the other hand, ice deeper down in a glacier moves more slowly. Some of the ice near the bottom of a large glacier might be from 5,000 to 20,000 years old. So, in this sense, some Alaskan glaciers are remnants of the ice age.
DB: You can ask us your science question at our website – earthsky.org. Thanks today to the Bureau of Land Management and to the National Fish and Wildlife Foundation – supporting the conservation of native fish, wildlife, plants and their habitats. We’re Block and Byrd for Earth and Sky.
Our thanks to the following individuals and institutions who assisted in the preparation of this script:
Dr. Keith Echelmeyer
Professor
Dept. of Geology and Geophysics
University of Alaska, Fairbanks
Dr. Dorothy K. Hall
Hydrological Sciences Branch
NASA Goddard Space Flight Center
Links
General Glaciology Links (International Glaciological Society – British Branch, University of LEEDS Dept of Geography)
All About Glaciers National Snow and Ice Data Center, World Data Center
Glacier Bay multimedia tour (NASA’s Goddard Space Flight Center)
Books and Ariticles
Sharp, Robert P., 1988. Living Ice: Understanding Glaciers and Glaciation.
Cambridge: Cambridge University Press.
Elias, Scott A., 1995. The Ice-Age History of Alaskan National Parks.
Washington, D.C.: Smithsonian Institution Press.
Erickson, Jon, 1996. Glacial Geology: How Ice Shapes the Land. New York:
Facts On File, Inc.
Broecker, Wallace S. and George H. Denton. “What drives glacial cycles?”
Scientific American (Jan. 90), pp. 49-56.
Hamilton, Thomas D., Katherine M. Reed, and Robert M. Thorson, Eds., 1986.
Glaciation in Alaska: The Geologic Record. Anchorage: Alaska Geological
Society.
Krimmel, Robert M. and Mark F. Meier, 1989. “Ice field trip T301: glaciers
and glaciology of Alaska.” IN Glacial Geology and Geomorphology of North
America (Field trips for the 28th International Geological Congress).
Author’s notes
Even the faster Alaskan glaciers can be considered remnants of the ice age – in the same way a river is considered the same feature year to year even though it is completely different water. We don’t re-name the Colorado River when all the water that was in it at one point in time has all flowed out.
Additional Teacher Resources
USDA Forest Service, Tongass National Forest, Forest Facts: Icefields and Glaciers
This site explores glaciers and glaciations in southeastern Alaska including the how glaciers start, what glaciers are composed of, the anatomy of a glacier, life around a glacier, and what will happen to glaciers in the future. Overall this is a good resource for students as introductory material.
National Snow and Ice Data Center; National Oceanic and Atmospheric Administration: All About Glaciers
This site is a great resource for all students studying any aspect of glaciers, glaciations, or the climatic forces that have created and eroded glaciers over time. The topics covered include how a glacier is formed, why glaciers move, what are the components of a glacier, where are glaciers located, what types of glaciers are there, how do glaciers affect the land, how do glaciers affect people, are glaciers dangerous, how do glaciers reflect climate and change, and quick facts about glaciers.
U.S. Geological Survey, Water Resources of Washington State. Glaciers and Snowpack
This report discusses how the long-term records of glacier changes provide information about climate variability. Also discussed is how glacial snowpacks have a great impact on atmospheric circulation and are an important source of water. The site also provides a link to the USGS benchmark glacier monitoring program.
