Sudden Death from Below: Undersea Super-Volcanoes

Located 1,500 km east of Japan, Shatsky Rise is as big as California. This underwater chain represents one of the largest supervolcanoes in the world: the top of Shatsky Rise lies three-and-a-half kilometres below the sea surface, while its base plunges to nearly six kilometres below the surface.

...‘About a dozen supervolcanoes exist on earth – some are found on land, while others lie at the bottom of the ocean. Those found on the seafloor are often referred to as ‘large oceanic plateaus,’ Sager adds. _CoalGeology

Supervolcanoes are nothing to sneeze at. Whether sitting in a continent -- such as the Yellowstone supervolcanoe -- or underwater, these massive dynamic geologic structures can radically restructure the shape of the geological and biological landscape.

The great Toba eruption 73,000 years ago on Sumatra deforested central India --3,000 miles away -- and almost drove pre-historic humans to extinction. Supervolcanoes are a very real hazard to large areas of the planet. It is quite possible for billions of humans to die in the global aftermath of a massive supervolcanic eruption -- which could go on for hundreds of years or longer.

Roughly a dozen supervolcanoes currently exist. Some are on land, while others lie at the bottom of the ocean. Each has produced several million cubic miles of lava — about three hundred times the volume of all the Great Lakes combined — dwarfing the amount of lava produced by the Hawaiian volcanoes or the Icelandic volcano that erupted recently.

These eruptions have dramatically shaped life on Earth, pumping huge amounts of ash, dust and gas into the atmosphere that have killed off species and altered global climate. Despite their global impact, the cause of the massive eruptions from supervolcanoes at times remains unknown. _LiveScience

“Supervolcanoes” have been blamed for multiple mass extinctions in Earth’s history, but the cause of their massive eruptions is unknown.

Despite their global impact, the eruptions’ origin and triggering mechanisms have remained unexplained. New data obtained during a recent Integrated Ocean Drilling Program (IODP) expedition in the Pacific Ocean may provide clues to unlocking this mystery.

To explore the origins of these seafloor giants, scientists drilled into a large, 145 million-year-old underwater volcanic mountain chain off the coast of Japan.

...“Seafloor supervolcanoes are characterized by the eruption of enormous volumes of lava,” says William Sager of Texas A&M University, who led the expedition with co-chief scientist Takashi Sano of Japan’s National Museum of Nature and Science in Tokyo. “Studying their formation is critical to understanding the processes of volcanism, and the movement of material from Earth’s interior to its surface.”

About a dozen supervolcanoes exist on Earth; some are on land, while others lie at the bottom of the ocean. Those found on the seafloor are often referred to as large oceanic plateaus.

Current scientific thinking suggests that these supervolcanoes were caused by eruptions over a period of a few million years or less–a rapid pace in geologic time. _WattsupWithThat

Anyone living within a few thousand miles of an erupting super-volcano -- particularly on the downwind side -- may find survival almost impossible. But even people living on the opposite side of the globe from the eruption could find their sunlight and food supplies shut down by the distant eruption. Global climate would cool abruptly for an extended period of time. Outdoor growing seasons -- in the light of an already feeble sun -- would shorten to a period of several weeks.

The civilised communities that survive would be those with ample electrical supplies -- probably nuclear power with access to a lot of fuel -- and the ability to grow food indoors under artificial lighting.

This is true existential risk. Not global warming doom, not peak oil doom, not Doombama dark ages or Islamic Jihadi dark ages doom. The risk from supervolcanoes compares to the risk of a large comet or asteroid collision, or the risk from an abrupt change of solar output. It is even comparable to the risk from an invading alien starfaring civilisation intent on transforming Earth's entire ecology to suit its needs.

One day you're humming along, minding your own business. The next day you're covered by a thousand feet of hot ash. What's a Terran to do?

Five SuperVolcanoes to watch