Northeast of Ruapehu, Mt Ngauruhoe (2287m) is the national park's youngest volcano and the most classically perfect in its conical shape. Its first eruptions are thought to have occurred 2500 years ago. Until 1975 Ngauruhoe had erupted at least every nine years, including a 1954 eruption that lasted 11 months and disgorged 6 million cu m of lava. Its steam vents have temporarily cooled, suggesting that the main vent has become blocked.
For all that, it's most famously known these days for its starring role as Mt Doom in Lord of the Rings.