Earth Lights.

“That earthlights exist is virtually beyond doubt. That they are linked in some way to tectonic activity and to sudden surges in ambient magnetic field strength is on the way to becoming firmly established. But what remains unknown is the mechanism by which the lights are created and sustained. In some cases, earthlights have been seen to persist for up to two hours. Whatever is behind the phenomenon, it is certainly not a sudden, momentary electrical discharge like that of a lightning strike.”