Lady Knox Geyser
Lady Knox Geyser, Waiotapu, New Zealand
This geyser erupts at 10:15 each day. It is set off by a person dumping some detergent into the geyser, which changes the surface tension of the hot water inside, causing it to erupt. This was initially discovered by some prison construction workers who tried washing their clothes in the hot water and added laundry soap, which gave them quite a surprise.
©Bill Yeaton