A dust devil?
Or similar, you can often see mini devils/twisters around the volcano, obviously due to temperature differences but still fascinating to watch when they occur, especially over the hot lava which then sends lots of sparks off.
119.4 m /391.7 feet asl
Sunny Dartford, NW Kent
Don't feed the Trolls!! When starved of attention they return to their dark caves or the dark recesses of bridges and will turn back to stone, silent again!