The Waimangu Volcanic Rift Valley is the hydrothermal system created on 10 June 1886 by the volcanic eruption of Mount Tarawera, on the North Island of New Zealand. It encompasses Lake Rotomahana, the site of the Pink and White Terraces, as well as the location of the Waimangu Geyser, which was active from 1900 to 1904. The area has been increasingly accessible as a tourist attraction and contains Frying Pan Lake, which is the largest hot spring in the world, and the steaming and usually pale blue Inferno Crater Lake, the largest geyser-like feature in the world although the geyser itself cannot be seen since it plays at the bottom of the lake.
Waimangu is a Māori-language word meaning "black water". This name comes from the water that was thrown up by the Waimangu Geyser, which was black with mud and rocks.
From the 1890s onwards, the valley has gradually been re-populated naturally by plants ranging from hot water-loving algae and bacteria to mosses and many species of native ferns, shrubs and trees.