What Causes A Supervolcano?
An artist’s depiction of magma build-up under the surface of a supervolcano, (www.fourwinds10.net)
We’ve all seen TV shows and disaster flicks portraying super-volcanic eruptions. The devastating blast of liquid magma ejected thousands of feet into the air, only to rain down upon unsuspecting mountainside towns and the conspiracy theorist’s RVs (driven by John Cusack), but few people understand the science and causes of actual super-volcanic eruptions.
What Is A Supervolcano?
An artist’s depiction of a super-volcanic eruption, (eden.uktv.co.uk)
The funny thing is, the term “supervolcano” doesn’t actually exist in the scientific lexicon of geologists of volcanologists. There isn’t even a minimum eruption size threshold for classifying a supervolcano. Nevertheless, the scientific community has effectively adopted the phrase for the purpose of “communicating science to the public.”
The term’s first usage is linked to an early 20th-century scientific debate about the geological history and features of the Three Sisters volcanic region of Oregon. However, it wasn’t really popularized until the year 2000, when the BBC television program Horizon used it in referring to eruptions that produce extremely large amounts of ejecta (a suggestive word that basically means “the stuff that’s tossed out during an eruption”). It’s this modern usage that generally applies the rule of “a volcano capable of producing a volcanic eruption with an ejecta mass greater than 1015 kg.”
Amidst the vast, ashy, gray areas of the terminology there is one general scientific consensus regarding two types of super-volcanic eruptions: “large igneous provinces” and “massive explosive eruptions.”
Type 1: Large Igneous Provinces
Icelandic eruption of 2014, (www.newsmedialinks.com)
Large igneous provinces (LIP) such as Iceland, the Siberian Traps, Deccan Traps, and the Ontong Java Plateau are extensive regions of basalts on a continental scale resulting from flood basalt eruptions. Say that three times fast.
The Réunion hotspot in the Indian Ocean is believed to have produced the Deccan Traps about 66 million years ago, an event that coincides with the Cretaceous–Paleogene extinction event. Although scientific consensus mostly agrees on a meteoric event during that period, some believe the volcanic activity may have caused environmental stresses on extant species up to the Cretaceous–Paleogene boundary. A one-two punch for life on planet Earth.
Additionally, the largest flood basalt event (the Siberian Traps) occurred around 250 million years ago and coincides with the largest known mass extinction in history, the Permian–Triassic extinction event; although, it is unknown whether it was completely responsible for that extinction event.
The thing about LIPs is that they are very active, but typically non-explosive. An unimaginable amount of gas and magma is released, but like a bulldozer pushing forward for geological advancement.
Type 2: Massive Explosive Eruptions
A graphic showing past Yellowstone eruptions, (www.news.com.au)
The go-to for stunning, nightmare fuel imagery, massive explosive eruptions are the ones most violent and instantaneous. They lie in hiding beneath the surface and leap up without warning, destroying hundreds of miles of surrounding land in a matter of hours. This is the kind of supervolcano that sits beneath Yellowstone National Park.
Geologists and volcanologists actually do have a scale of devastation for these types of volcanoes, kind of like the Fujita (F) scale for tornadoes or those hurricane “categories.” Known as the Volcanic Explosivity Index, or VEI, the scale ranges from level 0 to level 8, with a 9th level available if scientists ever classify a single volcanic event large enough. It is a logarithmic scale, meaning that an increase of one in VEI number is equivalent to a tenfold increase in volume of erupted material.
To give you some perspective, the Mt. Saint Helens eruption of 1980 that destroyed 200 houses, 47 bridges, 15 miles of railways, and 185 miles of highway (and was equivalent to 1,600 times the size of the atomic bomb dropped on Hiroshima) was only a VEI 5 eruption.
In conclusion, a supervolcano is ambiguous, yet terrifying. Unforeseeable, yet ever-ready to announce itself. The causes and classifications are as complex as predicting where a twister will touch down, and yet the repercussions stretch across all continents and timelines in the volatile history of our great blue dot in the sky. If the human race escapes such a fate in the near future, then we can consider ourselves lucky, but fretting over unknown possibilities is like digging a dull knife into your leg every morning: both futile and exhausting.
