Mount Gambier’s Volcano is overdue for an eruption
South-eastern Australia has 400 small volcanos, which have erupted in the past five million years, 20 within the last 40,000 years. It’s no wonder then that the region is long overdue for an eruption, considering the last eruption to occur in Mount Gambier was 5,000 years ago.
Mount Gambier, located between Adelaide and Melbourne, is famous for its Blue Lake, which is situated in one of four crater lakes within the maar volcano.
Professor Joyce from the University of Melbourne’s School of Earth Sciences says, “Although the volcanoes in the region don’t erupt on a regular sequence, the likelihood of an eruption is high given the average gap in the past has been 2,000 years.”
A maar volcano is produced when the rising basaltic magma comes in contact with groundwater. The interaction of hot and cold causes a massive explosion that shatters the surrounding rock and initiates volcanic eruptions. A tall cloud composed of gas, lava, steam and pieces of rock are torn from the vent and is billowed above the crater, which then rains ash and rock fragments across the countryside.
“Depending on the type of eruption, they could cause devastation to thousands of people,” says Professor Joyce.
Mount Gambier’s maar volcano has a wide funnel-shaped crater, which is 100 metres above sea level, ringed by a very low cone that gently slopes away from the crater. The cone is built up of layers of ash and large basalt lumps. Evidence of ash and rock fragments, from previous explosions, can be found throughout Mount Gambier.
With only two crater lakes remaining today, Blue Lake and Valley Lake, it is still highly dangerous for those who live in the area. The Blue Lake is 500 metres across and 70 metres deep and is the main water source for 30,000 people. The lake is replenished from the water stored in the limestone unconfined aquifer, where the watertable is able to rise and fall. However, the other two, Leg of Mutton and Brown Lake, has a confined aquifer, where the watertable is unable to move, and they have dried up over the past 40 years as the water table dropped.
Tourists, like Leigh, who thought the Blue Lake and the other three crater lakes “were amazing” is worried for the safety of others, “The earthquake we had last year made me realise the dangers for the people around volcanic areas.”
All volcanoes are associated with some form of seismicity,with subduction zones (Pacific rim volcanoes), spreading or rifting zones (East Africa, Iceland), or hot spots above mantle plumes (Hawaii).
“I think that communities who live close to volcanoes should always have an emergency plan,” said Leigh.
Professor Joyce said that communities neededto have knowledge of what to do if the volcano did erupt. “So far we have no action plans in place if eruptions occur. If they happen close to Melbourne or Geelong it could be hugely devastating. It is more likely however, that eruptions would occur further west, closer to areas such as Colac, Port Fairy, Portland and Mt Gambier.”
Vikki was thrilled when she visited the area three years ago. “I loved the Blue Lake. It was overwhelming the way it looked, just the way Mother Nature has created it.”
Some scientists believe the volcano is dormant and others say it’s extinct. However, there have been cases where scientists have believed a volcano was extinct, but later, shown signs of life. Like Mount Vesuvius for an example, a famous volcano in Italy was believed to be extinct, but it erupted in 79 A.D covering towns of Herculaneum and Pompeii with ash; only the roofs of houses weren’t covered and weren’t discovered until 1595. The last time it erupted was in 1944, during World War Two.
“If it were going to erupt it would show signs first,” says Vikki.
As the Blue Lake is sitting inside the maar volcano it is a time bomb waiting to happen. If the volcano does erupt and the rising basaltic magma comes in contact with the water there will be a huge explosion; putting thousands of people in danger. Since Mother Nature is unpredictable having an emergency plan will help save lives of people who live near volcanic areas. But the question is: why there isn’t an emergency plan in place already?