The world’s most famous supervolcano is the Yellowstone Caldera which is located in
Wyoming.
Yet, it is not the only supervolcano on the planet which is still active, as 8 more supervolcanoes
are present, such as Campi Flegrei in Italy.
Although the Australian mainland does contain two active volcanoes which have produced recent
eruptions, their eruptions were quite small.
Thus, it is quite interesting that a strip of land just northeast of the city of Melbourne
once contained a massive supervolcano.
One of its individual eruptions was so massive and catastrophic that in merely a week buried
a vast area in 1.2 kilometers thick of superheated rock.
The supervolcano I am referring to is known as the Cerberean Caldera, which today is located
partially in Lake Eildon National Park.
The remnants of this ancient supervolcano are the source rock of a decently sized tungsten
deposit.
The ancient Cerberean Caldera can be found 92 kilometers east northeast of Melbourne,
where it is centered just southeast of the city of Taggerty.
Although the rocks of this ancient supervolcano have been highly deformed and stretched over
time, its approximate caldera outline is shown on screen.
It measures 27 kilometer long and 21 kilometers wide, and was likely once a bit larger with
a more circular shape.
This caldera represents a giant collapse scar which originated from one of the planet's
most explosive eruptions during the Devonian era of geologic history.
Approximately 365 million years ago, what is now Australia was the easternmost landmass
of the supercontinent known as Godwana.
This landmass was connected to sections of South America, Africa, the Middle East, Antarctica,
and India.
At the time, two large volcanic arcs stretched across the eastern edge of the country, one
of which was located in Victoria.
This arc produces numerous stratovolcanoes of a basaltic andesite and andesite composition,
meaning that at the time numerous gray volcanoes covered the landscape along with associated
flank vents.
Some of these distinct volcanoes were unusually close to each other, which over time allowed
for unusually large underlying joint magma chambers to grow.
One such large magma chamber began to grow underlying the eventual Cerberean caldera,
where over time it leached material from the surrounding crust.
This caused the magma to become more silica rich, allowing for the nature and type of
associated volcanic eruption to change, producing lava dome forming dacite and rhyolite forming
eruptions.
During the end of this distinct phase of activity, several large caldera forming eruptions occurred,
depositing layers of a rock type known as ignimbrite in eruptions similar in size to
the 1991 eruption of Mount Pinatubo in the Philippines.
Then, eruptions seemingly paused for a period of several hundred thousand years, as a massive
magma chamber grew to an immense size and causing significant amounts of pressure to
build.
Finally, something caused a quick release of this pressure and a massive explosive eruption
on the surface began.
As several vents simultaneously erupted, a plume of ash shot 50 kilometers or 164,000
feet into the atmosphere.
Across the region, the day seemingly turned to night due to the quantity of falling ash
which blocked sunlight.
Simultaneously, pyroclastic flows raced across the surrounding landscape, travelling up mountains
and all topography.
These superheated flows traveled more than 100 kilometers distant, eradicating all vegetation
in their path and eventually reaching the modern city of Melbourne.
As dozens of meters thick of ash fell across much of Victoria, the eruption continued.
Then, due to the large volume of material erupted, a wide section of ground collapsed
downwards, forming a large caldera.
At its center, the eruption deposited a 1,290 meter or 4,232 foot thick layer of rock.
In total, 1,100 cubic kilometers of volcanic rock had been ejected in a true super-eruption.
Although no subsequent eruptions occurred from this supervolcano, volcanic activity
continued in Victoria during the Devonian period.
I want to note that this eruption occurred around the same time as the Late Devonian
Mass extinction event.
However, despite the vast magnitude of this eruption, it was likely insufficient to cause
a mass extinction.
Today, a portion of granodiorite rock in the southeastern section of the Cerberean caldera
contains quantities of wolframite which is an ore mineral of tungsten and fluorapatite
which is a beautiful crystal that contains the elements fluorine, oxygen, phosphorous,
and calcium.
I hope that you enjoyed this video.
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