But that’s suddenly changed, and they’re now moving between 360 and 720 inches a day (that is, 30 to 60 feet, every day).
The rare phenomenon began last fall some 12 miles uphill. That’s where the glacier initially started sliding, its smooth surface ice cracking under tremendous, hidden stresses. New crevasses opened and ice cliffs were pushed up in a chaotic jumble. The first witness was a pilot who spied the scene in March as he flew around the north side of Denali, the continent’s tallest mountain.
The Muldrow has been “surging” forward ever since, at speeds up to 100 times faster than normal….
Surges are one of the last mysteries for those who study glaciers, in part because they happen so infrequently and in just a fraction of places around the world. The activity is different from a glacier actually growing in size, and it can take decades for the right conditions to develop…. The prevailing theory of surges is that the natural advance of a glacier causes friction, which melts the deepest ice. Loose gravel traps the meltwater underneath. But as snow and ice accumulate in the glacier’s higher elevations, the mass there gets top heavy. A surge redistributes that mass to lower elevations, with the meltwater serving as a lubricant that helps the glacier pick up speed as it slides downhill.
This last happened with the Muldrow during the winter and spring of 1956-57. Given its record of surges roughly every 50 years, scientists had long anticipated the current event. Their concern is that a warming climate could spell disaster for future surges. “You wonder, ‘Are you going to ever be able to see the surge again?’ ” said Chad Hults, regional geologist for Alaska’s national parks. “I don’t know, because 50 years from now, you might lose enough glacier ice that even if it surges… you might not actually even be able to see any difference.”
For most of the glaciologists and geologists tracking today’s surge, it’s a once-in-a-lifetime thrill.
The article also reminds readers that “across the Alaska Range, glaciers are losing mass because of climate change.”
Read more of this story at Slashdot.