Named for Lady Constance Knox, a daughter of the 15th governor of New Zealand, Lady Knox Geyser is located in the North Island's Taupo Volcanic Zone. While this region is famous for a variety of fascinating geological phenomena, the Lady Knox Geyser is unique. Every day it erupts at precisely 10:15am, when a park guide induces it to do so - with soap.
Indeed, the soap is used to break the surface tension of the cold water in the geyser's upper chamber so that it will mix with the hot water in the lower chamber, which causes an 20 meter (65 feet) eruption that can last an hour. Stones have been placed around the opening in order to enhance the blast, and over the years, silica in the water has given the spout a nozzle-like appearance. You'll find it among the other natural marvels of the Wai-O-Tapu Thermal Wonderland.
Unlike many of the other thermal features of the area, the Lady Knox Geyser does not have a Maori name because it was discovered in the early 20th century - by prisoners who were washing their clothes. They triggered the jet when they dropped some soap in with the hot water!