India, Aug. 26 -- A wall of mud, rock and water tore through Nepal's northern Rasuwa district on Wednesday morning, killing at least 95 people and leaving 384 tourists missing, in a disaster officials on both sides of the Nepal-Tibet border are still working to fully understand. As rescue teams search the debris in both countries, the central question driving the investigation is what exactly unleashed the flood, and whether a mudslide, an earthquake, or a combination of the two was to blame.

What Do We Know So Far?

At around 8.30am local time, a huge volume of mud and rock appeared to collapse into a river system on the Himalayan border between Nepal and China's Tibet, sending a torrent of water downstream that destroyed houses, roads,...