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Prologue
AUSTRALIA began to break off from Antarctica 85 million years ago to commence its march northwards on a collision course with Asia. As the continent drifted north, its eastern side rode over a hot spot in Earth’s mantle. Every few million years the heat from the hot spot would be sufficient to punch through the surface and create a volcano.
The largest of these volcanoes was formed 23 million years ago in an area now south west of the Gold Coast. Eruptions of basalt and rhyolite over hundreds of thousands of years created a huge shield volcano standing two kilometres high and spreading out with a diameter of over a hundred kilometres.
Eventually the volcano was spent and Australia drifted further north away from the hot spot. The volcano began to erode. Australia continued to head northwards causing the Southern Ocean to widen. This formed the powerful circumpolar current to flow clockwise around Antarctica cooling Earth’s climate enough to create the series of ice ages we have been experiencing in the past few million years.
The vast rainforests that once covered Australia before the ice ages were gradually swept away by the dry eucalypt forests and deserts that now cover the country. Despite the dramatic changes some remnants of the ancient forests of Gondwana remain in small sky islands that have somehow preserved the climate of hundreds of millions of years ago.
The Tweed Volcano is one of these sky islands.
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