Three Ancient Volcanoes Discovered in Australia
Scientists at Monash University have announced the discovery of three previously unrecorded ancient volcanoes in the Hamilton area of the Newer Volcanics Province, Victoria, Australia.
The newly discovered volcanic complex Cas Maar: upper – the wide asymmetrical maar, about 900 m across; middle – the eastern maar-rim sequence showing two layers of spattery lava; bottom – lower sequence of spattery lavas (left) and upper sequence of spattery lavas and scoriaceous tuff showing sharp contact between the two materials (right). Image credit: J. A. Boyce et al.
The Newer Volcanics Province constitutes the most recent phase of volcanic activity in Australia, with eruptions spanning from largely 4.5 million to 5,000 years ago.
It covers an area of nearly 19,000 km2 in Victoria and South Australia, and, with over 400 volcanoes, features the youngest volcanoes in Australia including Mount Schank and Mount Gambier.
"Victoria's latest episode of volcanism began about 8 million years ago, and has helped to shape the landscape. The volcanic deposits, including basalt, are among the youngest rocks in Victoria but most people know little about them," explained Julie Boyce, a researcher with the Monash University's School of Geosciences and the lead author of a paper published in the Australian Journal of Earth Sciences.
"Though it's been more than 5,000 years since the last volcanic eruption in Australia, it's important that we understand where, when and how these volcanoes erupted. The province is still active, so there may be future eruptions."
The largest unrecorded volcano, named Cas Maar, is a substantial maar-cone volcanic complex identified 37 km east of Hamilton. It features a broad, low relief volcanic crater up to 0.9 km wide with a rim 30 m above the surrounding plains.
"The discoveries were made possible only by analyzing a combination of satellite photographs, detailed NASA models of the topography of the area and the distribution of magnetic minerals in the rocks, alongside site visits to build a detailed picture of the Hamilton region of the Newer Volcanics Province," Boyce said.
"Traditionally, volcanic sites are analyzed by one or two of these techniques. This is the first time that this multifaceted approach has been applied to the Newer Volcanics Province and potentially it could be used to study other volcanic provinces worldwide," she said.
The Newer Volcanics Province is considered active, as carbon dioxide is released from the Earth's mantle in several areas, where there is a large heat anomaly at depth. With an eruption frequency of one volcano every 10,800 years or less, future eruptions may yet occur.
"It's hoped that this multifaceted approach will lead to a better understanding of the distribution and nature of volcanism, allowing for more accurate hazard analysis and risk estimates for future eruptions."
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J. A. Boyce et al. Eruption centres of the Hamilton area of the Newer Volcanics Province, Victoria, Australia: pinpointing volcanoes from a multifaceted approach to landform mapping. Australian Journal of Earth Sciences, published online June 16, 2014; doi: 10.1080/08120099.2014.923508
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