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 or Mount Aso in Japan.
However, these supervolcanoes do not compare in size to those which existed in the distant
past.
One of these supervolcanoes once existed in what is now Canada for a period of 16 million
years.
It’s ancient eruptions produced 50 kilometer high plumes of ash, and erupted more than
3,000 cubic kilometers of molten rock in a span of less than 24 hours.
What I am referring to is the Blake River Megacaldera complex.
Today, the remnants of its supereruptions are the site of some of the world’s best
and largest copper, gold, and zinc deposits.
This video will discuss this volcanic complex, which is likely the oldest supervolcanoes
to form on the planet.
The Blake River Megacaldera can be found straddling the border of Quebec and Ontario, where it
is 200 kilometers north-northeast of the city of Sudbury.
The extent of this extinct supervolcano is truly massive.
It measures more than 100 kilometers long and 80 kilometers wide.
It contains a group of 3 massive calderas which formed in distinct eruptions approximately
2.7 billion years ago.
At the time in earths geologic history, there were no complex life forms, although primitive
life did exist through bacterial colonies such as stromatolite mounds.
The length of the planet’s day was only 11.5 hours, and the atmosphere contained no
oxygen.
Yet, underneath one of the early continents, a deep mantle plume had been rising through
the crust.
When it reached the surface, it began building two large shield volcanoes on the ocean floor.
Initially, these two volcanoes were small in size, and looked much like the Craters
of the Moon volcano does today.
However, after more than 1 million years of erupting, two towering shield volcanoes had
been constructed, rising above sea level.
Each of these volcanoes were approximately the size of Mauna Loa today, and contained
large summit calderas.
These volcanoes also had lengthy fissures and hot springs, which provided an ideal climate
for primitive life forms.
However, underneath these two distant volcanoes was a single, massive magma chamber.
Eventually, something caused a large section of the molten rock present in this magma chamber
to erupt onto the surface through a series of vents.
As a towering plume of ash shot into the atmosphere, pyroclastic flows raced across the barren
landscape, traveling for several hundred kilometers before they stopped.
Due to the large volume of material erupted, totaling more than 1,000 cubic kilometers
of molten rock, the underlying magma chamber was largely empty.
This caused an 80 by 40 kilometer wide section of ground to collapse downwards by several
hundred meters, forming a massive caldera which was later filled in by an ancient ocean.
In the aftermath of this eruption, a large central dome formed and was uplifted by more
than 1,000 meters, just barely breaking the ocean’s surface.
The next phase of activity began 2,704 million years ago, when a large central stratovolcano
was constructed out of the remains of this first caldera.
Its central peak had a bright red color, as it was mafic in composition much like Mount
Fuji.
Over the next 3 million years, this volcano along with its network of vents was built
into a towering stratovolcano.
Then, a massive eruption occurred.
Much of the underlying magma chamber drained to the southeast in a distant eruption, causing
the existing stratovolcano to collapse into a caldera.
This caldera measured 30 kilometers wide and 15 kilometers long.
The last stage of volcanism occurred 2,696 million years ago.
Deep on the ocean floor, a 20 kilometer wide caldera formed after a 3rd massive eruption.
At the edge of this caldera, large amounts of metal rich magmas were deposited in what
is termed a massive sulfide deposit.
Over the next several million years, these extensive ore deposits were covered by 8 kilometers
of volcanic rock.
Today, this ancient supervolcano is extensively mined for its unusual minerals, such as sylvanite
which contains gold, silver, and tellurium in its crystal structure.
One of the larger ore deposits in the overall structure is known as the Horne deposit and
by itself contains 2.5 billion pounds of copper and 11.6 million ounces of gold.
Thus, this area will be extensively mined for centuries to come due to the abundance
of its natural resources.
I hope that you enjoyed this video.
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