A quick trip back 1.3 billion years...

Australia has long been deemed to be a single intact continent which was considered to be an original part of Gondwanna. Recent studies now indicate this not to be the case. These studies have significant impact on the Pangea development. About 1300 million years ago the first three components of Australia came together to form the first segment of Australia as part of the Rodina super continent.

These were the North Australian Craton, the West Australian Craton and the South Australian Craton, sometimes referred to as the Mawson Craton. Subsequent to and during this time the centralian superbasin developed. This was an intracratonic basin comprised of marine and fluviatile sandstone. Around 750 million years ago the Rodina continent started to break up; during this time the centralian superbasin was broken into a number of smaller basins, but basically maintained its position and shape.

To all of those here who have seen the Pangea promotional video, the shape is consistent with that of the centralian superbasin. At some later stage, 500 million years or after, the eastern states arrived, most probably from Laurentia (now North America) leaving the centralian superbasin system intact but deformed to the east of the continent. The only place where the centralian superbasin is currently accessible is in Western Australia, where the Neoproterozoic sedimentary rocks formed from the marine and fluviatile sandstone are seen as a surface expression. This rock fits the criteria required by Pangea and is up to seven kilometres thick.

According to Dr. Peter Cook, “if the risk [from earthquakes] appears to be significant then the scientific review group, and no doubt Pangea, will need to be reassured, or the area eliminated from further consideration.”

If Dr. Cook means what he says, then Pangea can go home now. Gaull et al. (1990) identified the proposed site in the Great Victoria Desert as an earthquake source zone (Richter magnitude <5.9), with an offshoot to the Musgrave Ranges with the site of a 1986 earthquake of magnitude 6.0. They estimated that peak ground intensity (Modified Mercalli scale for cities) in the proposed region is VI (some structural damage) and to the east, in the Simpson Desert, VIII (moderate damage). These estimates correspond to a probability of 10% of being exceeded over a 50 year period and a return period of 500 years. The prediction from 1990 to 2040 is based on records for the past 100 or so years. To be valid, predictions longer than this would require correspondingly long records that sample thousand year events.

Seismologists (and weather prophets) do not predict longer spans, except to point out the greater expected intensity of the 10 000 year event. Crone et al. (1997) caution: “although they may be currently aseismic, faults in the current stress field could produce damaging earthquakes, often in unexpected places.”

Inescapably, predictions for the next 10 000 years would find the maximum credible earthquake (Yeats et al., 1997) to be much greater than the maximum recorded over the past 100 years.1

References

1. J.J. Veevers, “Disposal of British RADwaste at home and in antipodean Australia.” The Australian Geologist. August 1999. Pp.5.