On my trip back from Zebula yesterday I witnessed 'standing' thermals, made visible by the ash from veld fires! This was quite incredible to watch. I had always thought that these bubbles of hot air would form and then pop off the ground and, leaving a diminishing whirlwind tail behind them, rise into the sky as a large rising mass of air.
However, to witness these columns of continuously rising (and obviously rotating) air gave me a new perspective on thermals! As long as it took me to fly past the area (say 20 minutes) these same 'standing' columns of rising air just continued unabated, without moving their position on the ground!
My only regret now is not having intentionally flown through one and videoed the experience! We do this all the time, right, 'just that we are oblivious to their presence!!
My ASI was going 50 . . . 65 . . . 50 in the space of 10 seconds, with it feeling like the rear of my trike was being lifted by a large invisible hand!! 
Some of the video footage was so shaky due to the high ASI and associated vibrations of the wing!! 
