Supervolcano A supervolcano is any volcano capable of producing
a volcanic eruption with an ejecta volume greater than 1,000 km3 . This is thousands
of times larger than normal volcanic eruptions. Supervolcanoes can occur either when magma
in the mantle rises into the crust from a hotspot but is unable to break through the
crust, thus pressure builds in a large and growing magma pool until the crust is unable
to contain the pressure , but they can also form at convergent plate boundaries .
Although there are only a handful of Quaternary supervolcanoes, supervolcanic eruptions typically
cover huge areas with lava and volcanic ash and cause a long-lasting change to weather
(such as the triggering of a small ice age) sufficient to threaten species with extinction.
Terminology The origin of the term "supervolcano" is linked
to an early 20th-century scientific debate about the geological history and features
of the Three Sisters volcanic region of Oregon, United States. In 1925, Edwin T. Hodge suggested
that a very large volcano, which he named Mount Multnomah, had existed in that region.
He believed that several peaks in the Three Sisters area are the remnants left after Mount
Multnomah had been largely destroyed by violent volcanic explosions, similar to Mount Mazama.
In 1948, the possible existence of Mount Multnomah was ignored by volcanologist Howel Williams
in his book The Ancient Volcanoes of Oregon. The book was reviewed in 1949 by another volcano
scientist, F. M. Byers Jr. In the review, Byers refers to Mount Multnomah as a supervolcano.
Although Hodge's suggestion that Mount Multnomah is a supervolcano was rejected long ago, the
term "supervolcano" was popularised by the BBC popular science television program Horizon
in 2000 to refer to eruptions that produce extremely large amounts of ejecta.
Volcanologists and geologists do not refer to "supervolcanoes" in their scientific work,
since this is a blanket term that can be applied to a number of different geological conditions.
Since 2000, however, the term has been used by professionals when presenting to the public.
The term megacaldera is sometimes used for caldera supervolcanoes, such as the Blake
River Megacaldera Complex in the Abitibi greenstone belt of Ontario and Quebec, Canada. Eruptions
that rate VEI 8 are termed "super eruptions". Though there is no well-defined minimum explosive
size for a "supervolcano", there are at least two types of volcanic eruption that have been
identified as supervolcanoes: large igneous provinces and massive eruptions.
Large igneous provinces 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. When created,
these regions often occupy several thousand square kilometres and have volumes on the
order of millions of cubic kilometers. In most cases, the lavas are normally laid down
over several million years. They release large amounts of gases. The Réunion hotspot produced
the Deccan Traps about 66 million years ago, coincident with the Cretaceous–Paleogene
extinction event. The scientific consensus is that a meteor impact was the cause of the
extinction event, but the volcanic activity may have caused environmental stresses on
extant species up to the Cretaceous–Paleogene boundary. Additionally, the largest flood
basalt event (the Siberian Traps) occurred around 250 million years ago and was coincident
with the largest mass extinction in history, the Permian–Triassic extinction event, although
it is also unknown whether it was completely responsible for the extinction event.
Such outpourings are not explosive though fire fountains may occur. Many volcanologists
consider that Iceland may be a LIP that is currently being formed. The last major outpouring
occurred in 1783–84 from the Laki fissure which is approximately 40 km (25 mi) long.
An estimated 14 km3 (3.4 cu mi) of basaltic lava was poured out during the eruption.
The Ontong Java Plateau now has an area of about 2,000,000 km2 (770,000 sq mi), and
the province was at least 50% larger before the Manihiki and Hikurangi Plateaus broke
away. Massive explosive eruptions
Volcanic eruptions are classified using the Volcanic Explosivity Index, or VEI.
VEI – 8 eruptions are colossal events that throw out at least 1,000 km3 (240 cu mi)
Dense Rock Equivalent (DRE) of ejecta. VEI – 7 events eject at least 100 cubic
kilometres (24 cu mi) DRE. VEI – 7 or 8 eruptions are so powerful that
they often form circular calderas rather than cones because the downward withdrawal of magma
causes the overlying mass to collapse and fill the void magma chamber beneath.
One of the classic calderas is at Glen Coe in the Grampian Mountains of Scotland. First
described by Clough et al. (1909) its geology and volcanic succession have recently been
re-analysed in the light of new discoveries. There is an accompanying 1:25000 solid geology
map. By way of comparison, the 1980 Mount St. Helens
eruption was a VEI-5 with 1.2 km3 of ejecta. Both Mount Pinatubo in 1991 and Krakatoa in
1883 were VEI-6 with 10 and 25 km3 (2.4 and 6.0 cu mi) DRE, respectively. The death
toll recorded by the Dutch authorities in 1883 was 36,417, although some sources put
the estimate at more than 120,000 deaths. Known supereruptions
VEI 7 VEI-7 volcanic events, less colossal but still
supermassive, have occurred in the geological past. The only ones in historic times are
Tambora, in 1815, Lake Taupo, Hatepe, around 180 CE, and possibly Baekdu Mountain, 969 CE
± 20 years and the Minoan eruption of Santorini. Ongoing studies
A hypothetical Campanian ignimbrite super-eruption around 40,000 years ago has been suggested
as having contributed to the demise of the Neanderthal, based on evidence from Mezmaiskaya
cave in the Caucasus Mountains of southern Russia.
A Diamond anvil cell simulation at the European Synchrotron Radiation Facility and computer
modeling at the University of Bristol showed that it was possible for a supervolcano eruption
to occur simply through the slow addition of liquid magma without any external trigger
such as an earthquake that might provide warning of the event.
Media portrayal In 2004, Naked Science TV show aired supervolcano
on National Geographic Channel. In 2005, a two-part television docudrama called
Supervolcano aired on BBC One, the Discovery Channel, and other television networks worldwide.
Nova featured an episode "Mystery of the Megavolcano" in September 2006 examining such eruptions
in the last 100,000 years. In 2006, the Sci Fi Channel aired the documentary
Countdown to Doomsday which featured a segment called "Supervolcano". The same year, ABC
News aired the documentary Last Days on Earth, which featured a segment called "Supervolcano".
Also in 2006, the Syfy Channel series Stargate Atlantis episode entitled "Inferno" featured
a supervolcano as the major plot device. Dr. Rodney McKay, one of the main characters,
uses Yellowstone National Park to describe what a supervolcano is.
In the episode "Humanity" of the television drama Young Justice, the team must relieve
the pressure of the Yellowstone Caldera supervolcano caused by Red Volcano before an eruption with
the potential for mass extinction takes place. In 2009, the apocalypse-themed film 2012 featured
the super-eruption of the massive Yellowstone Caldera, a result of the Earth's core heating
up. This made most of the United States uninhabitable. In 2011, the SyFy series Warehouse 13 featured
an episode entitled Reset in which a supervolcano, specifically the Yellowstone Caldera, plays
an important role. In December 2011, author Harry Turtledove
published Supervolcano: Eruption, the first of a planned four-novel series about events
leading up to and following a fictional eruption of the Yellowstone Caldera. The second book
in the series, Supervolcano: All Fall Down, was published in December 2012. The third
book Supervolcano: Things Fall Apart, was published in December 2013. The last volume
Supervolcano: Maelstrom is scheduled for 2014. At the end of Terry Pratchett and Stephen
Baxter's novel Long War the Yellowstone Caldera erupts. The aftermath will be featured in
the next volume, Long Mars.