Geophysical signatures of the Taranaki and Tongariro volcanoes reflect similarities in their age, composition and
hydrothermal histories, but also reflect differences in host rock settings and edifice evolution. The Taranaki volcanoes
have strong positive gravity anomalies showing that their edifices largely consist of dense andesite which reflects
substantial lava production or dyke injection during construction and that large sub-edifice dykelstock complexes occur.
In contrast, the Tongariro volcanoes have strong negative gravity anomalies indicating low density edifices of
volcaniclastic material; no sub-edifice intrusions can be identified, probably because of the lack of density contrast with
host basement rocks. Strong positive magnetic anomalies over the younger cones can mainly be attributed to near-surface
andesite lavas or dykes whereas subdued magnetic effects are associated with hydrothermally altered zones within both
edifices and sub-edifice intrusions.