Ngaruhoe and Tongariro from the west. Photo courtesy Ruapehu Tourism

Origin of volcanism in the Tongariro Volcanic Centre (TVC): the subduction of the Pacific Plate underneath the North Island (edge of the Indo-Australian Plate) Type of volcanism: andesitic, with a mixture of explosive phases forming loose layers (tephra), and quieter lava flows
History of the TVC: Volcanic activity can be traced back to the early Quaternary (2 million years), and has not stopped, the latest eruptions of Ruapehu dating to 1996
Physical features: - 2 major volcanoes: Ruapehu (2797 m, 9176 ft) and Tongariro (1959 m, 6457 ft); Ngaruhoe (2291 m, 7516ft) is a lateral cone on Tongariro - several smaller surrounding volcanoes and cones (Pihanga, Hauhungatahi, Pukekaikiore, Pukeonake) - several crater lakes, either active (Ruapehu) or extinct (Tama Lakes, Blue Lake)
- geothermal areas: Ketetahi Springs, Red Crater and Te Mari Crater on Tongariro - Many lava flows: for instance the dark 1954 flows on the sides of Ngaruhoe, Te Mari flow on Tongariro - Several glaciers on Ruapehu Click here for a tour of the landforms and landscapes of Tongariro National Park

Books and references presented:

Potton, Craig, 1987. Tongariro - A Sacred Gift. Landsdowne Press and Craig Potton 

Karen Williams, 1996: Ruapehu erupts. Godwit Publishing. 

Bruce Houghton, Vince Neall and David Johnston, 1996. Eruption! Mt Ruapehu Awakens. Viking.

Lois Anderson, 1995. Tongariro, a Volcanic Environment. Longman Paul.

Karen Williams, 1998. Volcanoes of the South Wind - Fieldguide to the Volcanoes of Tongariro National park. Tongariro Natural History Society.

Geoffrey J. Cox and Bruce W. Houghton, 1999. Restless Country - Volcanoes and Earthquakes of New Zealand. HarperCollins
 

Other relevant bibliographical references:
 

The Fold of the Land - New Zealand's National Parks from the air	Homer, Lloyd and Les Molloy	Allen & Unwin and Institute of Nuclear and Geological Sciences	1988
The Tongariro National Park, New Zealand	Cowan, James	Ferguson & Osborn Ltd for the Tongariro National park Board	1927
North Island Volcanism Tour Guides	Houghton, Bruce and S.D. Weaver	DSIR and New Zealand Geographical Society	1986
Ruapehu Awakens: the 1945 Eruption of Ruapehu	Jonhston, David and Vince Neall	Massey University, Institute of Nuclear and Geological Sciences and The Science Centre	1995
Volcanoes and Earthquakes	Ell, Gordon	The Bush Press	1996
Volcanoes of Tongariro National park	Gregg, D. R.	New Zealand Geological Survey Handbook, Information Series 28	1961
Volcanoes of the South Wind - Fieldguide to the Volcanoes of Tongariro National park	Karen Williams, 1998	Tongariro Natural History Society.	1998
The Restless Land - Stories of Tongariro national Park	Rob Greenaway	Tongariro National Park Board	1981
The Weather and Climate of the Tongariro Region	Thompson, C.S.	New Zealand Meteorological Service, Misc. Publ. 115 (14)	1984