RESEARCHERS have discovered the first evidence of kilometre-scale buried volcanoes in the waters of the Otway Basin.
Subscribe now for unlimited access.
$0/
(min cost $0)
or signup to continue reading
Yakup Niyazi from Deakin Warrnambool's School of Life and Environmental Sciences, Centre for Integrative Ecology, lead the groundbreaking study.
He found 19 volcanoes, ranging from 90 to 400 metres in height and 1.6-8 kilometres in diameter.
We found these beautiful, gigantic volcanoes.
- Yakup Niyazi, Deakin Warrnambool Campus
"These buried volcanoes are part of what is called the Older Volcanic Province," Mr Niyazi said.
"Those volcanoes that we can see on the surface, such as the Mount Gambier, Tower Hill, and the Mount Leura in Camperdown, are very young, and belong to the newer volcanoes that erupted between five million years to recently.
"But the volcanoes I found in the continental shelf area between King Island and Cape Otway, are very old.
"I found 19 volcanic cones, and two of them are 37-million-years-old, six of them are 27-million-years-old and the rest are 20-million-years-old."
"I found 19 volcano cones from three periods of eruption - 37 million years ago, 27 million years ago and another at 20 million years ago."
Those three periods are also known as the late Eocene, mid-Oligocene, and early Miocene.
Mr Niyazi said they were very well preserved.
"If you've seen the mountain at Camperdown, which is only around 300 metres high, you can imagine how big these new discovered volcanoes are. Some of these volcanoes under the sea floor are likely 400 metres high and six kilometres wide.
"It's the first time they have been found in this area."
Similar discoveries have been made in the neighbouring Bight and Bass basins, but such large and well-preserved volcanoes have not been documented in this region before.
Mr Niyazi and his team found them in the Prawn Platform, in the offshore Otway Basin.
Analysis suggests they are shield volcanoes and are believed to have been triggered by the accelerated northward movement of the Australian plate - around seven centimetres per year - since the late Eocene, associated with the differences of earth crust thickness in the larger area.
"We used advanced seismic reflection imaging techniques that are similar to medical ultrasound or CT scanning to map the hidden features underground.
"This seismic reflection data covers thousands of square kilometers, and can image the subsurface up to several kilometres deep. Therefore, we can have the full information of what's buried beneath the ground.
"All the data was collected for industrial or scientific purposes by oil exploration companies and scientific expeditions.
"The availability of these commercial and scientific seismic reflection data-sets by Geoscience Australia and Geological Survey of Victoria, enabled the scientists to study and find something crucial to understand the geological evolution of the area.
"In many countries these kind of data-sets are not publicly available. We're lucky we have the Geological Survey of Victoria to find these beautiful, gigantic volcanoes."
The discovery of these buried volcanoes extends understanding of magmatism in south-eastern Australia, especially regarding the offshore extension of the Older Volcanics.
It also shows they can also pose a major risk during hydrocarbon exploration and represent potential geo-hazards if associated with shallow gas systems.
Mr Niyazi said all the newly-discovered volcanoes were extinct, but when they did erupt they would have been "huge, explosive eruptions, like Tower Hill or Camperdown."
"Some of these volcanoes I found were likely to have formed big islands such as the Lady Julia Percy Island near the coast of Port Fairy, and then experienced some aerial erosion before being fully buried.
"These were evidenced by the fact that some of the volcanoes are higher than the sea level of that area during that time, and erosional features such as gullies and troughs are found along the flanks of them.
"All the volcanoes erupted underwater, and at least 10 of them heaped above sea level and formed some kind of island, while nine of them did not reach the sea level.
When they erupt they can support the formation of a distinctive ecological system, he said.
"When they erupt, they can bring valuable minerals from rocks dissolved deep underground to the sea floor, and support the local ecological community in the long-term.
"They change the geomorphology of the sea floor and can create positive seabed features.
"When it's all flat the ocean currents can spread all ways, but once we have the high topography formed by a volcano, these currents cannot spread around so will be focused in one direction and change the oceanic currents."
The Otway Basin extends from South Australia to Victoria, and to the northwest coast of Tasmania.
"The reason I'm doing this research to give more meaning for the region - the volcanoes you see now on the surface do not belong to this same period, these ones have erupted totally and are buried underground," Mr Niyazi said.
"This kind of study you can see the full image of how intense the eruption was, the geological extensions and what actually coexists.
"The other volcanoes in the Bight and Bass are fed by the literal transportation of magma, whereas this area is directly from the magma chamber - that's very deep.
"This study extends our understanding and gives new insights to older volcanoes."
Mr Niyazi lives in Warrnambool with his wife and newborn child.
It took him about 10 months to complete the research paper, then a further 10 months for the publishing process, including peer reviews.
"I submitted the paper before my wife was pregnant, and it came out after she had the baby so this took longer than a baby," he said with a laugh.
"Before I came to Warrnambool I didn't know volcanoes, my expertise was in geophysical imaging to interpret what's underground.
"I didn't know I would find these beautiful volcanoes. When I found the data it was glorious.
"I want to dig more deeply into these volcanoes in the future."
His next paper will focus on up to 50 volcanoes discovered close to Warrnambool, Port Fairy and Portland.
Have you signed up to The Standard's daily newsletter and breaking news emails? You can register below and make sure you are up to date with everything that's happening in the south-west.