Australian researchers have discovered the longest chain of volcanoes in the world which runs along the east coast of the island continent. Another volcano on Tasmania is believed to also be connected to the chain.

Although geologists were aware of individual chains stretching north to south toward Australia’s eastern coast, they have recently discovered that there is a hotspot in the Earth’s mantle that connects them, making it the largest chain of volcanoes.

Australian National University researchers say this is because, what with the Australian continent being especially thick, volcanoes could only form in regions where the molten material encountered a surface thin enough to break through it. [See fantastic Photos of the World’s Wild Volcanoes]. But the scientists figured out that they were all surface manifestations of the same hotspot by studying their composition they all had the same chemical signature, with the volcanoes at the southern end of the track being younger than those at the north end. These are regions of unusually hot rock that spring from the boundary between the Earth’s core and the mantle, some 3,000 kilometres (1,864 miles) below the Earth’s surface.

To bolster their hypothesis, Davis and his colleagues used the fraction of radioactive argon isotopes (versions of argon with different atomic weights) to estimate when volcanic activity first appeared in each of these regions.

The eastern portion of Australia has always been known for its past volcanic activity, with several regions previously known to scientists. The surprising bit about the volcano track is that it has formed away from the boundaries of tectonic plates where most of the volcanoes are found across the globe.

The northernmost volcano was created at Cape Hillsborough 33 million years ago, with the shift in the Australian plate resulting in the plume pushing through in Victoria around 9 million years ago. As Australia has migrated northwards towards a hotspot in the Earth’s mantle, extreme pressure and heat in the mantle combined to melt the tectonic plates and form magma.

At around 130km underground, these plumes melt, breaching the outer layer of the Earth’s crust, called the lithosphere and creating visible volcanoes.

Leucitite is found in low-volume magmas that are rich in elements such as potassium, uranium and thorium, said co-author Professor Ian Campbell from the ANU Research School of Earth Sciences.

This discovery will allow scientists to understand the movements of the continents in the past, as well as the telltale signs of volcanic activity.