The theory of plate tectonics is based upon global observations of earthquakes
and volcanoes, which are concentrated in narrow bands on Earth, and rocks
and fossils that are very similar, but are now separated by vast distances.
It is widely accepted that the surface of the Earth is divided into about
twelve tectonic plates, with relative movements occurring at their boundaries.
We use modern methods to critically examine and advance the theory of
plate tectonics, and use the theory to determine what ancient motions
have occurred through New Zealand.
Download a 1.18 megabyte animation here.
We currently have three tasks within the objective:
1 Present plate motion (leader Dr. John Beavan): GPS measurements
from Islands around the South Pacific are used to test the rigidity of
the Pacific plate and to determine its motion over a number of years.
Its current rate of motion relative to the Australian plate is an essential
input to quantifying New Zealand's earthquake hazard.
2 History of plate motion (leader Dr. Rupert Sutherland): A wide
range of observations and new methods are used to assess the history of
plate motions in the South Pacific over several millions of years, and
to assess assumptions regarding long-term plate rigidity. The work allows
predictions of motion through New Zealand to be compared with observations,
and provides useful geological predictions, where no relevant observations
exist. Results underpin a wide range of other studies and are used by
the GNS petroleum research program and the GNS minerals research programme.
3 Antarctic deformation (leader Dr. Nick Mortimer): Antarctica is a key piece in the South Pacific jig-saw of tectonic plates. A better understanding of Antarctic deformation allows us to: reconcile global plate motions with models of convection in the Earth; better predict New Zealand plate motion (task 2); and interpret ancient Antarctic environments, which is essential input for understanding global climate change. Typically we dispatch a geological or geophysical field party to Antarctica every 2-3 years, with the intervening time taken up with data analysis, publication and planning.
Geophysicists investigate crustal thickness and seismicity beneath the Transantarctic Mountains. Geologists check whether surface lineaments really are faults, find out which way they have moved, and collect nearby rock samples for radiometric dating to help establish when the faults moved. In three field seasons since 1997-98 we have found that many of the more obvious onland faults in Victoria Land are actually much older than the uplift of the range. This suggests that either the big young faults must be offshore and/or the range mainly came up without fault control.
Our last expedition was to the North Victoria Land coast in the 2005-06 field season. Analysis of greywacke and volcanic rocks is currently underway.
Selected publications
Aitken, J. Plate tectonics for curious kiwis. Institute of Geological
& Nuclear Sciences, Lower Hutt.
Beavan, J., Tregoning, P., Bevis, M., Kato, T., Meertens, C., Motion
and rigidity of the Pacific Plate and implications for plate boundary
deformation, Journal of Geophysical Research, B, Solid Earth and Planets
107: 2261-2275, 2002.
Steinberger, B., Sutherland, R., O'Connell, R.J., 2004. Prediction
of Emperor-Hawaii seamount locations from a revised model of global plate
motion and mantle flow. Nature 430: 167-173.
Mortimer, N.; Forsyth, P.J.; Turnbull, I.M. 2002: Reassessment
of faults in the Wilson Piedmont Glacier area : implications for age and
style of Transantarctic Mountains uplift. In International Symposium on
Antarctic Earth Sciences (8th : 1999 : Victoria University of Wellington,
NZ). Pp. 207-213.
Bannister, S.C.; Yu, J.; Leitner, B.; Kennett, B.L.N. 2003: Variations
in crustal structure across the transition from west to east Antarctica,
Southern Victoria Land. Geophysical journal international 155(3): 870-884.
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GNS research
Follow the links above to individual research project pages.