Today’s Image of the Day from NASA Earth Observatory features Lituya Bay, a fjord on the southeastern coast of Alaska.
In August of 2020, a strong current containing trees, muddy water, and chunks of ice was seen rushing against the tide near the head of the bay. These events are known as glacial lake outburst floods (GLOFs), or jökulhlaups.
“We can see clearly using Sentinel 2, Landsat 8, and Planet Labs imagery that a huge lake that had been dammed by Lituya Glacier drained abruptly in mid-August,” explained Bretwood “Hig” Higman, a geologist with Ground Truth Alaska.
Desolation Lake, along with stream channels that run through the delta and into Lituya Bay, were significantly altered.
“It appears that this massive outburst flood traveled underneath the Lituya Glacier, emerging from under its south end onto the gravel delta that now separates the glacier from Lituya Bay,” said National Park Service geologist Michael Loso.
“The lake level dropped at least 60 meters (200 feet), implying a total flood volume of about half a cubic kilometer of water. For comparison, that is nearly an hour’s worth of average flow from the world’s most voluminous river: the Amazon.”
According to NASA, satellite images show that at least twelve similar glacial lake outburst floods have occurred since 2004.
“The amount of sediment pushed out from under the glacier by these events is really impressive, perhaps over 10 million cubic meters per event,” said Higman. “That has been enough to build a broad delta over parts of the bay that were 100 meters (300 feet) deep only a few decades ago.”
Image Credit: NASA Earth Observatory