Blackfoot and Jackson Glaciers

Lisa McKeon, USGS


What is a glacier?

Glaciers are formed when more snow falls in winter than melts in summer. As snow accumulates over many seasons it becomes ice. The weight from snow and ice causes the bottom layers to move, fashioning a frozen river of snow and ice that slowly flows across the landscape, eroding and shaping it into unique landforms. When this process is reversed, the glaciers retreat back up the mountain. The amazing mountains and valleys of Glacier National Park were sculpted by the action of glaciers over hundreds of thousands of years of glacial advance and retreat.

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Look! Get up close and personal with a glacier! See the parts of a glacier and how they move. You'll even see some photos taken in Glacier at Views of the National Parks.

Park visitors viewing melt pond

NPS Photo


What is going on with Glacier's glaciers?

In 1850, at the end of the Little Ice Age, there were an estimated 150 glaciers in the area that is now Glacier National Park. By 1968, these had been reduced to around 50. Today the number of glaciers in the park is 25, many of which are mere remnants of what they once were. Rapid retreat of mountain glaciers is not just happening in the park, but is occurring worldwide. If the current rate of warming persists, scientists predict the glaciers in Glacier National Park will be completely gone by the year 2030, if not earlier.

Listen to U.S. Geological Survey (USGS) Research Ecologist Dan Fagre explain climate change research underway in Glacier National Park.

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Check out the USGS Glacier Animation simulation to see how climate change may change Glacier National Park!

sperry glacier
Sperry Glacier

USGS Photo


Climate Change

While Earth's climate is known to have changed in the past due to natural causes, the warming trend over the last few decades is primarily the result of human activities. Of major concern is the buildup of carbon dioxide and other "greenhouse gases" in the atmosphere. Greenhouse gases hold heat in the atmosphere that would otherwise radiate back out into space. While the greenhouse effect is what has made life on Earth possible, these gases are now increasing at an alarming rate. Since the beginning of the industrial revolution, the carbon dioxide concentration in the atmosphere has increased by 30%. Human activities that release carbon dioxide are burning of fossil fuels, harvesting and burning trees, and land conversion to cities and agriculture.

The advance and retreat of glaciers is strongly tied to temperature and precipitation and is a simple, but effective, way to monitor climate change. USGS scientists are documenting glacial change through data collection and photography. The photography project involves finding historic photographs of Glacier National Park's glaciers, taking copies of these photos into the field to determine the exact vantage point of the picture, then taking another photo of the glacier. A collection of these striking repeat photographs can be viewed and downloaded on the USGS Repeat Photography Project site.

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Look! Read about climate change impacts in national parks across the country and find out how YOU can make a difference at Climate Change In National Parks!

Contact the Park

Mailing Address:

PO Box 128
West Glacier, MT 59936


(406) 888-7800
Phones are generally staffed Monday through Friday from 8:00am to 4:30pm.

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