Auckland University researchers have discovered that magma beneath Rangitoto Island is still warm, even though it last erupted around 600 years ago.
The finding helps scientists better understand what could happen if Auckland’s largest volcano erupts again. The study was led by PhD student Alutsyah Luthfian, with support from Associate Professor Mila Adam.
The team detected a hidden hydrothermal system which is circulating underground water heated by the magma. By measuring natural electrical signals under the island, scientists found patterns showing warm water mixing with colder seawater. This discovery suggests the solidified magma continues to release heat.
Similar underground activity has been seen at volcanoes in Japan and Italy, but researchers were surprised to find Rangitoto still hot after so many centuries. “We really thought 600 years was long enough for the magma to cool,” said Adam. “At the surface, all you see is forest, but underground the water is still hot.”
Despite the discovery, scientists stressed there is no danger of an eruption. “It’s not a warning sign,” Adam explained. “It just shows Rangitoto is a little less dormant than we believed.”
The research will help experts model how long it takes magma to cool after eruptions.
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