Scientists Explore Origins of 'Supervolcanoes' on the Sea Floor

Apr 09, 2010
JOIDES Resolution departing from Yokohama, Japan, on the Shatsky Rise expedition. Credit: John Beck, IODP/TAMU

(PhysOrg.com) -- "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.

IODP Expedition 324: Shatsky Rise Formation took place onboard the scientific ocean JOIDES Resolution from September 4 to November 4, 2009. Preliminary results of the voyage are emerging.

"'Supervolcanoes' emitted large amounts of gases and particles into the atmosphere, and re-paved the ocean floor," says Rodey Batiza, marine geosciences section head in the National Science Foundation (NSF)'s Division of Ocean Sciences, which co-funded the research.

The result?

"Loss of species, increased greenhouse gases in the atmosphere, and changes in ," says Batiza.

In fall 2009, an international team of scientists participating in IODP Expedition 324 drilled five sites in the . They studied the origin of the 145 million-year-old Shatsky Rise volcanic mountain chain.

Located 1,500 kilometers (930 miles) east of Japan, Shatsky Rise measures roughly the size of California.

This underwater mountain chain is one of the largest supervolcanoes in the world: the top of Shatsky Rise lies three and a half kilometers (about two miles) below the sea's surface, while its base plunges to nearly six kilometers (four miles) beneath the surface.

Shatsky Rise is composed of layers of hardened lava, with individual that are up to 23 meters (75 feet) thick.

"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.

Each of these supervolcanoes produced several million cubic kilometers of lava--about three hundred times the volume of all the Great Lakes combined--dwarfing the volume of lava produced by the largest present-day volcanoes in places like Hawaii.

Since the 1960s, geologists have debated the formation and origin of these large oceanic plateaus. The mystery lies in the origin of the magma, molten rock that forms within the Earth.

A magma source rising from deep within the Earth has a different chemical composition than magma that forms just below Earth's crust. Some large oceanic plateaus show signs of a deep-mantle origin. Others exhibit chemical signatures indicative of magma from a much shallower depth.

The IODP Shatsky Rise expedition focused on deciphering the relationship between supervolcano formation and the boundaries of tectonic plates, crucial to understanding what triggers supervolcano formation.

A widely-accepted explanation for oceanic plateaus is that they form when magma in the form of a "plume head" rises from deep within the Earth to the surface.

An alternative theory suggests that large oceanic plateaus can originate at the intersection of three tectonic plates, known as a "triple junction."

Shatsky Rise could play a key role in this debate, because it formed at a triple junction. However, it also displays characteristics that could be explained by the plume head model.

"Shatsky Rise is one of the best places in the world to study the origin of supervolcanoes," says Sager. "What makes Shatsky Rise unique is that it's the only to have formed during a time when Earth's magnetic field reversed frequently."

This process creates "magnetic stripe" patterns in the . "We can use these magnetic stripes to decipher the timing of the eruption," says Sager, "and the spatial relationship of Shatsky Rise to the surrounding tectonic plates and triple junctions."

Sediments and microfossils collected during the expedition indicate that parts of the Shatsky Rise plateau were at one time at or above sea level, and formed an archipelago during the early Cretaceous period (about 145 million years ago).

Shipboard lab studies show that much of the lava erupted rapidly, and that Shatsky Rise formed at or near the equator.

As analyses continue, data collected during this expedition will help scientists resolve the 50 year-old debate about the origin and nature of large oceanic plateaus.

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StillWind
1 / 5 (5) Apr 09, 2010
Of course Shatsky's was above the surface. There were no deep oceans during the Cretaceous, and since it was a much smaller Earth, it was much closer to the equator.
It's way past time that Geologists re-aligned with the Expanding Earth theory, and get off the silly Plate Tectonic nonsense.
CarolinaScotsman
5 / 5 (2) Apr 09, 2010
It's way past time that Geologists re-aligned with the Expanding Earth theory, and get off the silly Plate Tectonic nonsense.


Currently, one of the major proponets for expanding earth is Neal Adams. His credentials? He's a comic book artist. With a background like that, who could doubt him?
Caliban
1.5 / 5 (2) Apr 09, 2010
Expanding Earth. Feh. How does X amount of matter magically transform into X+Y amount of matter? Unless you are proposing some very extensive bombardment/accretion scenario, then take the "Expanding Earth" "Hypothesis" somewhere else.

These supervolcanoes aren't quite as mysterious as the article seems to imply they are. They can mainly be understood in the light of fluid dynamics, with regards to temperature/density/pressure, in terms of these fluids "intruding" or being "injected" into the crustal(seafloor and/or continental) overburden.

The only real, persistent mystery is what causes these deep-mantle Plumes to form, and to continue to exist over such long periods of time?
Parsec
2 / 5 (1) Apr 09, 2010
The only real, persistent mystery is what causes these deep-mantle Plumes to form, and to continue to exist over such long periods of time?


They didn't need to exist for a really long time. A few millions years of dumping the lava, followed by extinction, means that an enormous plume could have existed just like the plume under Hawaii.
Caliban
2 / 5 (2) Apr 09, 2010
Yeah, except that the plume under Hawaii, and a number of others, have persisted for tens or even hundreds of millions of years, which is what, to my mind, makes them exceptional.

The mere fact that many of these supervolcanoes exist at plate boundary/subduction/spreading zones shouldn't really come as a surprise.

Also, the possibility exists that the Shatsky feature may have originated as a result of some tectonically-driven(non-"plumogenic") local fracturing in the crust that just is no longer apparent, or even some sort of impact-type fracturing.

The answer is, as yet, still waitng to be uncovered. But at least they're working on it.
Shootist
2.3 / 5 (3) Apr 10, 2010
"Loss of species, increased greenhouse gases in the atmosphere, and changes in ocean circulation," says Batiza.

The ironic thing is, one of these volcanoes releases more 'pollution' during one eruption than mankind has in his entire existence.

rwinners
1 / 5 (2) Apr 11, 2010
There is probably more than one explanation. How about random fluctuations in heat energy within the planet? Or, random thinning of the earth's crust do to plate movements? Take Yellowstone, for instance. The NA plate was pushed up due to subduction of the Pacific Plate. This large movement created volcanic activity within the Rocky Mountains. I think it would be reasonable to believe that Yellowstone was also created by the same upheaval.
out7x
not rated yet Apr 15, 2010
Yellowstone is a well known hotspot under the crust, just like Hawaii.