In the rugged North Cascade Mountains of Washington State, no one likely knows this glacier better than Mauri Pelto, who says, "My life has been shaped by this ice."

For more than 40 years, Pelto, a glaciologist and a professor at Nichols College in Massachusetts, has returned to this remote wilderness. "We got 6,000 measurements on this glacier," he said.

Today, the crunch of footsteps in the snow is now rivaled by the sound of melting ice. "It's always melting off," he said. "The crevasses are changing. We can hear the water flowing under our feet."

For more than 40 years Mauri Pelto has been studying the shrinking glaciers in the rugged North Cascade Mountains of Washington State. CBS News

Pelto founded the North Cascade Glacier Climate Project as a grad student in 1984. He vowed

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