Thursday, February 07, 2008

South Island drawn with new technology

Crown research institute GNS Science has published a geological map and companion book covering a 24,000sq km slab of the central South Island, from South Westland across much of Canterbury.

The 1:250,000 scale map contains greater detail than existing geological maps of the area, released in the 1960s, and has been compiled using Geographic Information Systems (GIS) technology and published and unpublished research.

But compiler and GNS Dunedin geologist Dr Simon Cox said the map, which cost about $1.5 million to produce, was already out of date.

"On Sunday the week before last, a large rock avalanche fell off Vampire Peak in the Mount Cook area. We recorded it on our seismographs like a 2.5 (magnitude) earthquake," he said.

"I went up there the other day and there's a big rock pile over the Mueller Glacier. That shows to me the dynamics of the landforms."

The map uses cross-sections put together from seismic experiments carried out in the late 1990s to show rock structures up to 5km below the surface. It also records more than 70 types of gravel from glacial advances and retreats.

The accompanying text de scribes rock types and other deposits and highlights potential geological hazards and economic geology.

Cox said producing the map had been a "mammoth" job. It covered areas that had not been visited before by geologists.

Many geologists and field workers had been involved over the eight years, and support had been given by more than 20 organisations. Landowners and the Department of Conservation had allowed access and the use of huts, and helicopter companies had provided transport.

The compilation team had calculated where there were gaps in knowledge before doing the fieldwork. The result was a map that was a vast step forward from the earlier ones, Cox said.

"The first maps came out after about a couple of years of fieldwork, before (the theory of) plate tectonics had been accepted,'' he said.

"The new map shows over 1500 different faultlines over which that strain could be released.''

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