When people think of a large volcanic eruption, several specific volcanoes come to mind.
Mount Saint Helens in 1980.
Vesuvius in 79 AD.
Pinatubo in 1991.
However, none of these aforementioned large volcanic eruptions even compare to the topic
of this video.
In western Utah and eastern Nevada is a supervolcano responsible for the single largest explosive
volcanic eruption in the history of the planet.
This eruption was phenomenally large, and was equivalent in size to 5900 simultaneous
eruptions of Mount Saint Helens in 1980.
The volcano I am referring to is a little known supervolcano called Wah Wah Springs.
So, how did this volcano form?
How large were its eruptions?
This video will answer these two questions, and discuss this fascinating extinct volcano.
The reason why the Wah Wah Springs supervolcano exists is complex.
Around 40 million years ago, the Farallon tectonic Plate was subducting underneath the
North American plate at a very shallow angle.
Due to this shallow angle, very few volcanoes were created.
This process caused an extreme amount of compression, causing the uplift and formation of the rocky
mountains.
However, several million years later, something changed.
The Farallon tectonic plate suddenly snapped downwards at a much steeper angle in a process
called slab rollback.
This caused magma to rush upwards to fill the empty space previously occupied by the
tectonic plate.
Large volumes of magma than creeped through the crust, and erupted onto the surface through
incredibly large volume explosive eruptions.
This geologic event was referred to as the Mid tertiary ignimbrite flare up, which saw
the creation of dozens of supervolcanoes in a short timespan in the southwestern United
States.
One example of another supervolcano created during this period was the La Garita caldera
adjacent to the town of Creede within Colorado.
Around 31 million years ago, one section of crust underneath east central Nevada built
up a large magma chamber.
This chamber eventually expanded in size to contain several thousand cubic kilometers
of magma.
As a result, an immense amount of pressure began to build.
Then, 30 million years ago, this pressure was released through a catastrophic eruption.
The size of this eruption was unimaginably large, as it was equivalent in size to 281,000
simultaneous eruptions of Lassen Peak which occurred from 1914 to 1917.
As a plume of ash traveled more than 50 kilometers into the atmosphere, pyroclastic flows raced
across the surrounding landscape.
Due to how energetic the eruption was, these kilometer high pyroclastic flows even traveled
up mountains.
The pyroclastic flows from this eruption deposited several meters of ash within a radius of 130
miles or 210 kilometers.
Then, due to the large volume of material erupted, a 58 by 27 mile section of land collapsed
downwards, filling much of the underlying massive magma chamber.
In total, this eruption produced 5,900 cubic kilometers of volcanic rock, marking it as
the largest single explosive eruption to ever occur on the planet.
In the center of this eruption, deposits were measured at more than 15000 feet thick (4572
m).
You heard that correctly.
In some areas, more than 4.5 kilometers thick of ash and lava was deposited in the span
of only a few hours.
This was the most energetic event on the planet since an asteroid impacted the Yucatan Peninsula
66 million years ago, thus leading to the extinction of the non avian dinosaurs.
Today, the caldera formed by this massive eruption is not easily visible, as the area
was subsequently overlaid by several successive supereruptions and other smaller but still
large caldera forming eruptions.
One of these supereruptions occurred 29.2 million years ago, which emplaced 4400 cubic
kilometers of volcanic rock.
The last major eruption in this section of Utah occurred 18 million years ago, since
when the volcanic complex has become extinct.
However, the same area of Utah affected by this eruptive series is not completely void
of volcanic activity.
Recent small scale eruptions have occurred from three different volcanic systems in Saint
George, Panguitch Lake, and Flowell, one of which erupted less than 1,000 years ago.
As an exploration geologist, I want to note that the Wah Wah Springs caldera should technically
contain numerous ore bodies of precious metals due to the type of lava erupted.
However, so far the area has remained largely void of economic major mineral discoveries,
due to the sheer thickness of ash emplaced during this eruption.
I hope that you enjoyed this video!
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