The process that led to the demise of the lake is known as a permafrost thaw slump. It begins when rain and heat melt headwall ice, exposing previously frozen soil and sediment that is in turn washed away to uncover more ice, driving a cycle that over decades or mere years can eat away entire hillsides. A single slump can displace up to 10-million cubic meters of ice and sediment enough to fill the Toronto Blue Jays' stadium six times. The flow of this debris can create pools of sucking mud that behave like quicksand and have been known to trap large animals.
"The slumps we observe today develop in these landscapes and they are more abundant and much larger than they were in the recent past, so for northerners these are becoming increasingly important geohazards to be aware of," stated the NWT Geological Survey in a release.
On July 15, between 8 and 9 pm, the slumping permafrost that held back the unnamed lake finally gave way. The ensuing cascade gushed roughly 30,000 cubic meters of water in a flow that could have filled a dozen Olympic swimming pools. Although remote camera's captured the event, the extreme isolation of Fort McPherson, which sits roughly 1,800 miles due north of Vancouver, meant that news of the flood would not reach those studying the lake until weeks later.
