(CBS News) Two million people visit Montana's Glacier National Park each year, and most go to see one of the park's namesake masses of ice. But the glaciers are melting much faster than scientists predicted just a few years ago, and could be gone entirely in just a decade.
Over tens of thousands of years massive sheets of ice slowly slid and chewed away at the rock carving out these valleys. But now, these frozen forces of nature are in full-scale retreat.
"The glaciers are continuing to shrink every year and at some point they will be gone," said Dan Fagre, a scientist with the United States Geological Survey who's been studying glaciers in Glacier National Park for 20 years. "I can remember exactly where a lot of these glaciers used to be, and see how much smaller they are."
In just a few decades, many of the park's glaciers have shrunk dramatically. Since 1966, 11 of them have completely melted away. There were once 150 glaciers in the park. Now there are just 25, and scientists believe in the next 10 to 20 years, they could all be gone.
The glaciers have been shrinking since 1850. Yet scientists say climate change, fueled by human pollution, has made them melt quicker and more extreme. The average temperature in the park has risen two degrees. Spring arrives about three weeks earlier, and the snow pack has been declining for 50 years.
"The snow is melting faster than it's being added to so the glaciers are just getting smaller," said glacier guide Corrie Holloway. Holloway took CBS News across two turquoise lakes formed by glacial runoff and then led the crew on a hike five miles up the side of a mountain to the top of Grinell Glacier, one of the park's most iconic ice sheets. In 1938, it covered nearly an entire valley. Between 1981 and 2009, it started to quickly shrink.
Holloway said people are coming to the glacier now because they know they have a short time to see the glaciers. "We've made a lot of top 10 lists lately - you know that 'you have to come here before a certain time' before the glaciers melt and see the glaciers," she said.
Laurel Meeks, who first hiked to Grinell 23 years ago, is shocked by how much of it is gone. "It's quite interesting to see it change that fast," she said. "I just find that a glacier sounds pretty permanent, and all of a sudden it's like, 'no way it can't change that quickly,' and yet it is."
There could come a day when you'd have to travel quite a bit north to see glaciers, such as in Alaska. Five percent of the state is still covered in ice: there are about 2,000 major glaciers. Yet the twilight of Montana's glaciers is not just about the changing scenery.
"This is a huge portion of our fresh water on this Earth," Holloway said. "And when they're gone - we lose that. That's huge."
The glaciers and snow melt feed the streams and lakes, a lifeline for fish and the other animals, such as big horn sheep that call the area home. With hotter summers, some wild flowers are already disappearing. The forests are drier and more disease-ridden and there are more extreme wildfires. In 2003, 10 percent of the park burned.From the air, you can see the ashen scar stretch across entire hillsides and valleys.
Fagre said the park will look different 20 to 30 years from now. "It'll still be you know a terrific landscape to come and enjoy, but it will have been changed by climate change."