A fountain of lava suddenly erupts high into the air, reaching a height of 100 meters.
Lava from this fountain then falls back to the ground, generating a runny flow of molten
rock.
Over the next several months, this lava flow advances across the landscape, starting wildfires
and producing abundant volcanic gasses.
While what I just described might sound like something which might occur in a location
such as Iceland, believe it or not, this is exactly what occurred at a volcano in Australia
within Queensland a mere 13,000 years ago.
This eruption occurred at the Toomba Volcano, which assuming it erupted at the same rate
the fagradfsjall volcano did in Iceland during its 2021 eruption, emitted so much material
that its eruption was continuous for 31 years and 7.5 months.
During this timespan, lava flows coated the landscape in sections up to 120 kilometers
or 74.6 miles distant from its source vent, covering a grand total of 676 square kilometers
in a thick layer of black volcanic rock.
By the time this lengthy eruption had ended, a 70 meter or 230 foot tall volcanic cone
had been constructed at the eruption's primary vent.
Today, this fascinating volcano and its lava field which contain 10 cubic kilometers of
volcanic rock is so large that it can be easily spotted from orbit.
This is somewhat close in terms of volume to the 14 cubic kilometers of lava the Laki
vents of the Grimsvotn volcano in Iceland erupted during sections of 1783 and 1784,
which released so much volcanic gasses and aerosols around the planet, that it created
a famine which helped cause the French Revolution.
However, existing human populations were not as severely effected by the Toomba volcano's
eruption due to several factors.
For one, its eruption was 2 orders of magnitude less explosive than Laki, so various volcanic
products were less likely to end up traveling high into the atmosphere.
However, while Laki produced 14 cubic kilometers of lava during an 8 month long eruption it
took Toomba nearly 32 years to erupt a comparable 10 cubic kilometers.
This means that the gasses and aerosols it produced were dispersed in smaller amounts
compared to Laki as a certain threshold of material in the atmosphere is needed to cause
severe climatic and rainfall variations.
With this being said, why does the Toomba volcano exist in the first place?
The Toomba volcano is one of approximately 40 vents which exist in a 7,000 square kilometer
region known as the Nulla Volcanic Province.
This volcanic province has been active for a little more than 5 million years, with eruptions
occurring on average about once every 120,000 years.
These eruptions involved the creation of many other small shield volcanoes, with one remnant
vent from an extinct eruptive center visible 27 kilometers west of Toomba's highest point.
In another section of the volcanic field there appears to even be highly eroded lava flows
which are probably 100,000 to 200,000 years in age.
As a whole, we are unsure why exactly this volcanic field exists, but we know it does
not originate due to melting from plate subduction, a rift zone, or an underlying hotspot.
The Nulla Volcanic Province is merely one of 4 active and dormant volcanic fields spanning
the eastern half of Australia which have each produced volcanic eruptions at some point
during the last 20,000 years.
The other fields are the Newer Volcanics Province in Victoria and South Australia, the McBride
Volcanic Province in Queensland, and the Atherton Basalt Province in Queensland.
While much of the extinct Toomba volcano is located in the Great Basalt Wall National
Park, this name is actually somewhat misleading.
This volcano does not actually contain any basalt, but rather two very similar types
of slightly more alkali rich volcanic rock.
Most of the lava flow is made of the rock type trachybasalt with another small section
of it being composed of basanite.
Of course, the Great Trachybasalt or Basanite Wall National Park does not have the same
ring to the name.
Although the Toomba shield volcano will never erupt again there is always a possibility
that the next eruption in the Nulla field will open a new vent less than 1 kilometer
away from Toomba's primary vent during its last eruption or as much as 30 kilometers
away.
With this being said, there are rare circumstances where mongenetic vents do erupt more than
once.
This is why although Toomba could probably be classified as extinct, I am classifying
it along with the broader Nulla Volcanic Province which it is a part of as a dormant volcanic
complex.
Sadly, there is no public access to the Great Basalt Wall national park as it is surrounded
by private property, and people are specifically not allowed in the park so you cannot visit
it or walk/hike on the lava flows.
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