Australia – Researchers have discovered that Australia has the longest chain of volcanoes in one continent. It expands 1,240-miles across the place and was formed over 33 million years ago.
Although geologists were aware of individual chains stretching north to south toward Australia’s eastern coast, they have recently discovered that there is in fact a hotspot in the Earth’s mantle that connects them, making it the largest chain of volcanoes.
It expands from Whitsundays in North Queensland all the way to the island of Tasmania. “This track, which we’ve named the Cosgrove hotspot track, is nearly three times as long as the famous Yellowstone hotspot tracks on the North American continent,” said study leader Rhodri Davies of the Australian National University.
The ancient string of volcanoes in Australia was created by a hotspot – a narrow upwelling of hot rock from 1,800 miles beneath the surface at the core-mantle boundary -, instead of being formed at the boundaries of tectonic plates like most volcanoes. This characteristic and the fact of being in the fastest moving continent on Earth, made it possible for the chain of volcanoes to be formed far from the plate’s boundaries.
How did they find it?
Researchers from the study looked at 15 extinct volcanoes in the continent’s east that were known to line up in a general north-to-south track. Davies and his team suspected that the Australian volcanism had the same source: a mantle plume that melted the crust while the Australian plate moved northward over millions of years.
“We realized that the same hotspot had caused volcanoes in the Whitsundays and the central Victoria region, and also some rare features in New South Wales, roughly halfway between them,” Davies explained.
Is it dangerous?
The findings of the study are important mainly because they help scientists understand volcanism on other countries and from earlier periods in Earth’s history. However, it does not mean a bigger risk than before.
Researchers found that sections of the track have no volcanic activity because the Australian continent is too thick. To form magma, the hot rock in mantle plumes would have to melt by rising close enough to the Earth’s surface, but the solid outer layer in the continent is too thick to allow it.
Volcanic activity can only occur if the Earth’s solid outer layer, called the lithosphere, which is thinner that 130km. However, Davies said that the mantle plume that formed the Australian volcanoes may still exist under the sea northwest of Tasmania.
“There is some seismicity in this region, there’s been some earthquakes around that location recently which does hint that something is going on there, but we haven’t been able to find any seamounts or volcanic regions at present,” Davies said.