Pipes have now been put in place in Lake Nyos and nearby Lake Monoun to siphon water from the lower layers up to the surface and allow the CO2 at the bottom of the lake to slowly bubble out, preventing a repeat of 1986 tragedy.

BBC: 1986: Hundreds gassed in Cameroon lake disaster

Changing temperatures in the lake during the winter could have brought stagnant water to the surface, thus asphyxiating entire schools of fish.

ECONOMIST: What killed Fossil Lake?

Scientists from Urals Federal University found 53 small meteorites on the surface of the lake and believe a larger fragment is under water, said Viktor Grokhovsky, the scientist who led the effort.

CNN: Russian scientists track down fragments of Urals meteor

Detailed studies of the surface indicate that these were formed by a lake caused by the flow of underground water that periodically made its way to the bottom of the crater.

FORBES: NASA Finds Remains Of Ancient Martian Lake