Other common triggers for snow and ice avalanches are rainfall, earthquakes and even animals. These are unlikely to have been triggers this morning at Khumbu Icefall.
A factor that may be playing a role is climate, which as changed a lot since the first Everest expeditions almost a century ago. Warmer temperatures and changes in snowfall just add another layer to the already complex picture of the Khumbu Icefall.
"Global warming isn't helping," Turnbull said.
Worldwide, most mountain glaciers are receding due to human-caused climate change, according to climate scientists and glaciologists. Those in the Himalayas are no exception, although there are regional variations there, according to Ann Rowan of the British Geological Survey.
"We see acceleration of mass loss since the 1990s in the eastern Himalaya glaciers," said Rowan.
That's the part of the Himalaya that includes Everest. It's also the part that's most affected by the Indian monsoons, she said.
So with all of this instability on so many levels, why do people still traverse the deadly Khumbu Icefall? It's simply matter of it being the least dangerous of some very dangerous options, Turnbull said. It's the lesser evil, but evil nonetheless.