CAPTION - Australia

The Ups and Downs of Australia.

This movie shows what happens to the surface of the Earth in the vicinity of Australia from the Early Cretaceous to the present. Although the model was a calculation of the whole mantle with the changing tectonic plates on the surface, this animation just shows what happens on the surface as a function of time. The purpose of the modeling was to understand the physical basis for two of the most extreme paradoxes in the southern hemisphere which are not explained by plate tectonics: the anomolous marine flooding of Australia in the early Cretceous (and the rapid withdrawal of the seas during the Cretaceous global sea level maximum) and the existence of a cold spot along the oceanic spreading center south of Australia.

The model simulated what happens to the ancient subduction zone which surrounded Gondwanaland but which turned off in the Late Jurassic/Early Cretaceous. In the animation, the darker blue to purple regions are topographically lowest. Initially, about 120 million years ago, the eastern interior of Australia becomes flooded with a shallow sea and as Australia moves toward the east, this region of dynamic depression migrates to the west. Eventually, the south east Indian ridge opens up over the ancient slab. The predicted and observed mantle downwellings occur in the same place.

To view our animation again, press here, or to download different versions of the animation go here. This work was undertaken in collaboration with Dietmar Mueller in Sydney and Louis Moresi now a Professor at Monash University.

Reference

Gurnis, M., Mueller, R. D., and Moresi,. L., Dynamics of Cretaceous vertical motion of Australia and the Australian-Antarctic discordance, Science 279, 1499-1504, 1998.

Gurnis, M., Sculpting the earth from inside out, Scientific American, 284, No. 3, 40-47, 2001. [Updated and reprinted in Our Ever Changing Earth, Scientific American, 56-63, 2005.]

Additional references of related material can be found here.

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