© Milo Barham, University of Western AustraliaWell travelled: these zircon crystals took a 2300-kilometre trip
A blast from the past? The east coast of Australia was once lined by volcanoes that were so explosive they could shoot sand-sized particles 2300 kilometres - all the way across to the west coast.
The volcanic activity occurred 100 million years ago, at a time when New Zealand began tearing away from Australia's eastern edge.
Until recently, the
only evidence of the scale of these eruptions were the 20-kilometre-wide dormant craters and the solidified lava flows left behind.But now,
Milo Barham at Curtin University in Western Australia and his colleagues have found that these eastern Australian volcanoes flung material to the other side of the country.
Crystal cluesThe researchers were drilling beneath the Nullarbor plain in remote Western Australia when they
discovered sand-sized zircon crystals that did not match any of the region's typical rock compositions.Instead, the crystals matched volcanic rock in the Whitsundays area on the
country's north-east coast in both age and geochemical make-up."We didn't find anything else from the east coast - just these very distinctive grains," says Barham. "Initially, we thought there might be some volcanism in Western Australia, but we couldn't find any evidence."
Two clues ruled out the possibility that river systems had carried the zircon crystals across the country: they were so well preserved and fossils in the rocks indicated that the crystals were of an identical age.
Staggering powerThe finding points to the sheer force of the east coast volcanoes, says Barham. The
eruptions would have been tens to hundreds of times more powerful than any documented in human history. An equivalent eruption today would be heard in the west coast city of Perth.
Tremendous volcanic activity was happening all around the world 100 millions of years ago due to the disintegration of the supercontinent Gondwana, says
Scott Bryan at Queensland University of Technology in Brisbane.
Modern volcanoes can spew fine particles of ash that are carried by winds over large distances, as happened in 2010 when Iceland's
Eyjafjallajökull volcano released an ash plume that grounded flights across Europe.
But they lack the power to hurl larger particles thousands of kilometres.The biggest known super-eruption occurred from
Toba volcano in Indonesia 75,000 years ago. This propelled sand-sized particles over a 2700-kilometre radius.
Barham's work
hints that Australia's east coast volcanoes may have been in a similar league, says Bryan. "
It reinforces the potential scale of these eruptions."Journal reference: Geology, DOI: 10.1130/G38000.1
the site newgeology.us speaks to the tremendous force that separated Gondwana land and drove India north, and SA & NA west. Specifically how Australia was spun off turning 90 degrees so that the coastal line that faced Africa was turned to the East. It is significant that this east southern tip of Africa is where the diamond mines are located, as well as gold. Tremendous energy was expended here and now we find proof.