The track begins at the Mangatepopo end, at 1,120 meters elevation, and finishes at Ketetahi on the northern side at 760 meters - a net descent that determines the direction most people walk. The journey takes about seven hours in good weather, longer in winter or when walked in reverse. From Mangatepopo Hut, the terrain starts gently before ascending steeply to the Tongariro saddle. Then comes a succession of descents and ascents through two different craters, past the Emerald Lakes - pools tinted vivid green by dissolved volcanic minerals - and along the edge of Blue Lake, which is sacred to the Maori and designated tapu. The final two hours involve a long descent down Tongariro's northern flank, past the Ketetahi Hot Springs, which sit on 38 hectares of private Ngati Tuwharetoa land that has never been part of the national park. Access to the springs is prohibited; in 2007, a person who entered the closed area was badly burned.

Most of the crossing traverses terrain that looks more like another planet than a hiking trail. Solidified lava flows give way to loose tephra - volcanic ash and lapilli that shifts underfoot. Lava bombs, some weighing tons, sit where they landed decades or centuries ago. Fumaroles hiss along several sections, venting steam and sulphur dioxide and depositing yellow crystal crusts at their edges. The lakes and pools are deeply colored by dissolved minerals, their hues ranging from emerald to turquoise depending on chemistry and light. Some springs emit near-boiling water. There are no guaranteed fresh water sources on the route; the natural water is tainted with dissolved metals and minerals from the volcanic activity, and the springs can be scalding. Underfoot, the terrain alternates between sharp-edged volcanic rock and loose ash that has been compacted by moisture into a gritty, shifting surface. The landscape is beautiful and hostile in equal measure.

The three volcanoes surrounding the crossing - Tongariro, Ngauruhoe, and Ruapehu - are all highly active, and the trail passes directly through the hazard zone. In August 2012, the Te Maari craters erupted 10,000 cubic meters of ash and hurled blocks up to a meter in diameter across the track. The Ketetahi Hut, 1.5 kilometers from the craters, had its roof damaged. About 75 percent of the track lies within three kilometers of Te Maari. The crossing was closed. In November 2012, Te Maari erupted again, sending an ash cloud 4,000 meters high in five minutes. Roughly 100 people were in the vicinity, including a school group of 20 thirteen-year-olds from Gulf Harbour. No one was injured, but the track closed for four more days. The prevailing westerly winds normally carry ash away from the track, but when mixed with rain the ash forms a gritty mud that covers everything. Fumaroles remain active around the Te Maari rim, and the smell of sulphur is strong near the craters.

Climbing Mount Ngauruhoe as a side trip from the crossing is no longer permitted, at the request of the local iwi, and track markings to the summit have been removed. The mountain is tapu. This intersection of volcanic hazard and cultural authority defines the crossing's character: it is a place where the earth is actively reshaping itself and where the people who have lived with these mountains for centuries ask visitors to tread carefully. Winter crossings require ice axes, crampons, and serious navigational skill, as visibility can drop to ten meters and buried poles vanish under snow. Several companies offer guided walks for those without alpine experience. The Department of Conservation recommends leaving your car at Whakapapa Village and using shuttle services to the trailheads, partly because of vehicle theft at the remote Mangatepopo car park. Summer crowds can reach 2,000 people per day, turning a volcanic wilderness into something closer to a queue. But step off the main trail and the silence returns, broken only by the hiss of fumaroles and the wind across bare rock.