Glaciers are slow moving masses of ice formed from snowfall over many years. Although they may appear to be motionless, they are constantly changing. This can easily be seen when the glaciers are photographed over time. Throughout history, glaciers have gone through cycles of major expansion and retreat that last 40,000 to 100,000 years. These cycles are also known as glacials (ice ages) and interglacials (temperate periods).

In March of 2009, an ecologist at Glacier National Park announced that the glaciers inside the park may become obsolete by 2020, endangering plant and animal life.National Geographic: No More Glaciers in Glacier National Park by 2020? (March 2, 2009)

In recent years, glaciers have been melting and moving at a much faster rate, alarming the scientific and environmental communities. Glaciers are affected by changes in the global climate and in turn also affect the climate with their own changes. Because of this, it is feared that their rapid melting may be a warning of upcoming, drastic environmental change.

1. "Receding and wasting glaciers are a telltale sign of global climate change"—Jeff Kargel, USGS
2. "There are many canaries emerging in the climate change coal mine. The glaciers are perhaps among those making the most noise, and it is absolutely essential that everyone sits up and takes notice."—BBC News