I had the opportunity to take a weekend off and head to Seattle. On the way back, I was seated in a window seat, and was treated to one of the more spectacular and rare views that one experiences in Alaska: The view of the Kenai Mountains by air.

The coastal mountains of Alaska guard the interior of the state from the moisture of the Gulf of Alaska and the Pacific Ocean, and in doing so, pile up some impressive snow, which then turns to ice and fills vast valleys with glaciers. These glaciers creep down the valleys and either terminate into a lake or river, or plunge all the way to the sea, forming the sight that many guests to Alaska have come to expect, large chunks of ice falling into an otherwise-glassy bay.

Another way to look at these glaciers is that they exist in an area where the Ice Age never ended. These are the last remnants of the thousands of years of continental glaciation, and are just now retreating into the alpine areas of Alaska.

Most people think that the ice age has been over for thousands of years. But in a significant part of Alaska (as well as other far northern and southern regions), the ice continues today as it has for millenia.

One of the things that has scientists so concerned about global warming is that many of the glaciers in Alaska and in other places have been historically stable – their rate of retreat has been slow, or oscillated between advance and retreat. However, in the last thirty to fifty years, many glaciers have shown a dramatic retreat as their rate of growth has not matched their melting. In fact, there are a number of places around Alaska where a guest can get instant feedback of the rate of glacial retreat. If you visit Exit Glacier near Seward, as you drive up the road to the visitor center, you’ll see wooden signs along the road, that list the location of the terminus of the glacier by year. On the slopes of Mt. McKinley, one can see the lateral moraines where the Ruth Glacier has pushed rocks and gravel to the side, and how the glacier has since melted away from the moraines, leaving walls of gravel dozens or hundreds of feet high.

Alaska’s glaciers are not in danger of disappearing in our lifetimes. But when we talk about change in a geologic time frame, these changes are occurring essentially instantaneously.