The Tongariro Massif is a complex arrangement of cones - some eroded by the ice age 6500 years ago, and some formed since. The most recent vent of Tongariro is Mt. Ngauruhoe.

There has been considerable activity from Tongariro in the last 2000 years, since 1855 there have been several eruptions from the Upper Te Maari Crater and the Red Crater. There is a continuous steam discharge from Ketetahi on the northern face of Tongariro. Ketetahi releases about the same energy as the Wairakei Geothermal Power Station in Taupo which supplies 3% of New Zealand's electricity. There are a dozen craters on Tongariro. The Northern Crater - the biggest crater - is a kilometer across. Some of the explosion pits on Tongariro have filled with water, giving a brightly coloured contrast to the surrounding landscape. Activity from Ketetahi and the Red Crater has been continuous since observation began.