Drainage of Supraglacial Lake (Before)
On July 17, 2014, a magnitude earthquake struck beneath Seward Glacier in northwestern Canada, 99 kilometers (62 miles) north-northwest of Yakutat, Alaska. High-altitude NASA flights over the region just before and after the event provided an uncommon view of an earthquake's effect on the snow-and-ice covered landscape. Images suggest that the earthquake might have prompted the draining of a supraglacial lake. Images from July 16 and 21 show dramatic changes in the amount of melt water pooled on top of the ice adjacent to Seward Glacier. This is an image of the lake on July 16. The July 21 photo suggests that much of the lake drained through a moulin, a vertical shaft down through the glacier. Possible moulins appear in the lake's center and to the left of the lake. When melt water travels through a glacier's plumbing, the ice responds. In this case, it appears to have lifted up and formed a mound in center of the lake. The uplift displaced the remaining water, changing the shape of the shoreline. It is probable, but not a certainty, that this change was caused by the quake; supraglacial lakes are ephemeral, and they can fill and drain on short timescales even without earthquakes or other dramatic events.
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Photo credit: © Photo Researchers / Alamy / Afripics
License: Licensed
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