The longest chain of continental volcanoes in the world was recently discovered in Australia. It stretches from near Mackay in Queensland down to Cosgrove in Victoria.

Don’t be alarmed. These volcanoes aren’t going to erupt anytime soon. It has been millions of years since any of the volcanoes in the chain have erupted. We’ve known about each individual volcano for a long time, but didn’t realise they were related.

A team of scientists had a hunch that these volcanoes were linked, so they decided to investigate. The first clue was that all the volcanoes lay very close to a straight line. The volcanoes were also lined up in order of age – older volcanoes in the north, and younger ones in the south.

Since they erupted one after the other, the team thought that they might all have the same cause. Say there was one volcano that moved slowly down Australia, erupting as it went. The team calculated the speed and direction that such a volcano would move and found it matched Australia’s continental drift. Australia is moving towards Indonesia at about seven centimetres a year. It was like the volcano was staying still, while Australia moved over the top!

This explained a lot, but there was still one mystery. In some areas there were lots of volcanoes, but in other areas there were none. Why? The scientists used seismic data to measure the thickness of the Earth’s crust, the hard outer layer that sits on top the mantle. Areas with lots of volcanoes had a thin crust, less than 100 kilometres thick. In areas with no volcanoes, the crust was much thicker – over 150 kilometres thick.

The volcano chain has been named the Cosgrove hotspot track.

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