Waimangu Volcanic Rift Valley is the hydro thermal system created as the direct result of the volcanic eruption of Mount Tarawera on 10 June 1886. It includes Lake Rotomahana, the former site of the Pink and White Terraces. It was the location of the Waimangu Geyser which was active from 1901 to 1904.
The name 'Waimangu' means 'black waters' in Māori, the indigenous language of New Zealand. This name comes from the water that was thrown up by the famous Waimangu Geyser, which was black with mud and rocks.