We think that we know the surface of the Earth pretty well but it continues to surprise me. Xeni Jardin describes a gas crater in Turkmenistan that has been burning for over forty years.
It came into being in 1971 when the ground under a drilling rig used by geologists from the Soviet Union collapsed, revealing a cavern filled with natural gas. The geologists thought that it would be safest to set the gas on fire to prevent poisonous gases from spewing into the atmosphere. And it is still burning, drawing visitors to the site known to the locals as “The Door to Hell”.
Jardin links to a site where you can see more photos.