Professor Dave Prior
The thing about rocks is they have features with a huge range of scales in them. And no microscopical kind of rock is really a lot of use unless you can relate it back to the bigger scale, so for us in our study of the Alpine Fault, the biggest scale feature is our fault zone which is a kilometre wide by 500 kilometres long by going down to 20–25 kilometres depth, which is a very big scale feature. And if I’ve got a field of view 10 micrometres in a microscope, I want to know how that 10 micrometre bit relates to the Alpine Fault zone. There’s too much scale difference to try and draw a picture of 10 microns on the scale of the whole Alpine Fault zone, so the continuity of scale is that I will know where that 10 micron field of view is in a picture of say 100 microns field of view and that I’ll know where it is with a picture of 1 millimetre field of view. And that could all be on a scanning electron microscope, and then that 1 millimetre field of view, I’ll know where it is in a 1 centimetre field of view on the polarising microscope, and the 1 centimetre field of view, I know where that is looking at a whole thin section which is several centimetres long. And then I know where that thin section comes from in the rock because I’ve got a square I’ve drawn on the rock, and I know where the rocks come from in the ground and how it links up to other units. I could get some information from the 10 micron field of view by itself but it’s incredibly devalued if I don’t have that continuity back to its biggest scale context.
Professor David Prior, Department of Geology, University of Otago.
Satellite map of South Island, courtesy of NASA.
Aerial still of Alpine Fault, by Lloyd Homer, courtesy of GNS Science Limited.
Rock micrographs and still of rock, courtesy of Dr Virginia Toy, University of Otago.
Still of rock cutting and Southern Alps, courtesy of Professor David Prior.