This is a marvellous and enjoyable one-day walk through a volcanic lunar landscape. Although if the weather is poor you will probably see nothing more than a white out and very little scenery. So check the weather before setting out because hut wardens can't organise transport if you turn back to Mangatepopo Hut.
The Volcanic Plateau comprises two massive volcanoes: Tongariro (1967m) and Ruapehu (2797m). Ngauruhoe (2287m) is considered to be a vent of the Tongariro Volcano.
It is not a difficult or especially long walk, although one section is quite strenuous. This section is a piece of cake. It is only 30 mins uphill then along through South Crater and then the climb up onto the Red Crater top with the Tongariro Summit turn off. Then from there it is all downhill to Ketetahi Hut.
The trip across South Crater on a fine day is a marvellous wonder. The trip has awesome views of craters, the Emerald Lakes, Blue Lake. The track has options at certain points along the track where you can do optional side trips that are worth every minute that you add to your track time. These options include such things as climbing the massif of Ngauruhoe, detouring over to Soda Springs, climbing Tongariro: you can choose. However you can just walk the crossing not doing any options, be at Ketetahi Hut by 11:30am. Again on a bad day don't be deterred by bad weather just stay on the track and keep your cool and enjoy it.
Two hours before the track end, you will reach the Ketetahi Hut, here you are able to stop for lunch and move on or spend a night. Then from Ketetahi if you choose to spend a night, which has had a fine day, the sunset is well worth the day's hard work. Then it is a smiple walk down to the carpark and then a wait for your transport. Again the views at Ketetahi are amazing but I won't say anymore. I shall let you do the walk.