When people hear the term supervolcano, they tend to think of Yellowstone in Wyoming, or
Toba in Indonesia.
However, these are not the only supervolcanoes on the planet.
Within Colorado is an ancient clustering of supervolcanoes near the town of Creede.
One of these volcanoes produced the largest volcanic eruption on the planet of the last
30 million years.
The volcano I am referring to is the La Garita Caldera, which is truly massive in size.
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 La Garita caldera 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.
Around 29 million years ago, one section of crust underneath southwest Colorado 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, 28 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 5,000
simultaneous eruptions of Mount Saint Helens in 1980.
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.
Although we aren't sure of the full extent of the eruption, these pyroclastic flows likely
traveled up to 322 kilometers or 200 miles away, resulting in an extreme level of destruction.
Ash from this eruption fell over the entirety of what is now the United States.
Then, due to the extremely high volume of material erupted, totalling about 5,000 cubic
kilometer of volcanic rock, a massive section of the volcano collapsed downwards to fill
the nearly empty magma chamber.
This formed a massive 35 by 75 kilometer wide caldera.
The eruption which had just taken place was the 2nd largest volcanic eruptions known to
have ever occurred on the planet.
It was 5 times larger than the last supereruption from Yellowstone.
An area approximately the size of Massachusetts was covered with an average thickness of 100
meters or 330 feet of ash and volcanic rock.
However, the story of the La Garita Caldera does not end here, as a large volume of magma
still remained in the underlying magma chamber.
This remaining lava eventually caused 7 additional supereruptions, of which 6 occurred in the
boundaries formed by the existing caldera.
Here is a time-lapse of when and where these eruptions occurred.
All of these eruptions produced volumes of ash in the hundreds of cubic kilometers.
The most notable of these smaller calderas is the Creede Caldera, which was the last
to form 26.3 million years ago.
This caldera was rather circular, and is still easily visible in satellite imagery today.
In the aftermath of its supereruption, a large resurgent lava dome formed in the caldera's
center thus forming a rounded mass of volcanic rock.
Today, this massive volcanic complex is extinct.
In a large area surrounding the town of Creede, you can see the vast volume of ash and volcanic
rock deposited by this eruptive series.
However, the best place to view the deposits of this era are in the Wheeler Geologic area,
whose coordinates I have placed on screen.
There, you can observe towering eroded columns of volcanic ash surrounded by dense forest.
It is truly an impressive site to give a sense of scale of the eruptions which formed them.
I hope that you enjoyed this video!
If you would like to request a specific topic, please leave a comment below!
Additionally, if you wish to support this channel, consider becoming a patron on patreon.