Quiescent and paroxysmally eruptive mud volcanoes are present on the Raukumara Peninsula of New Zealand. They extrude early Tertiary bentonitic mud with a few boulders from beneath a cover of late Tertiary sedimentary rocks, of which the aggregate thickness is about 20,000 ft (6,100 m). The quiescent ones are low cones and mounds of soft mud and they emit saline water and natural gas, mainly methane. Eruptions of the Hangaroa River and Mangaehu Stream mud volcanoes have been violent, and in 1930 the latter threw mud and rocks about 300 ft (92 m) into the air. Other violent disturbances off the east coast are interpreted as submarine mud-volcano eruptions.

New Zealand's mud volcanoes have many features in common with those in other parts of the world, in particular their association with a thick, rapidly deposited succession of Tertiary or Upper Cretaceous beds. Neither the pressure of natural gas being formed nor tectonic pressure alone can account for their occurrence, and it is believed, instead, that they are the surface manifestation of abnormally high pore-fluid pressures caused by compaction. Boreholes drilled near the north coast of Hawke Bay encountered pressures of this kind which approached the overburden pressure, particularly in the bentonitic mudstone of the lower Tertiary.

It has been suggested that high pore-fluid pressures could make feasible thrusting or gravitational gliding over very gentle slopes, and this hypothesis is in accord with the growing amount of field evidence for gravitational gliding on the Raukumara Peninsula. If mud volcanoes are an indication of abnormally high pore-fluid pressures, then they may provide a clue to the tectonic history of the areas in which they are found.