One million cubic miles from one single source. This is country building by mother Earth.
There has to be many more simply not understood. They may also be a lot more common. From the Hawaiian chain, we ate least know it
all works in geological time scales and is little real bother. It is still an awesome amount of fresh rock
and will make us rethink rock flows generally.
One can see this crashing up against another continent
quite easily and it helps us understand
our geography here on the West Coast.
Largest
Volcano on Earth Lurks Beneath Pacific Ocean
By By Becky Oskin
Called the Tamu
Massif, the enormous mound dwarfs the previous record holder, Hawaii's Mauna
Loa, and is only 25 percent smaller than Olympus Mons on Mars, the biggest
volcano in Earth's solar system, said William Sager, lead study author and a
geologist at the University of Houston.
"We think
this is a class of volcano that hasn't been recognized before," Sager
said. "The slopes are very shallow. If you were standing on this thing,
you would have a difficult time telling which way was downhill."
Tamu is 400 miles
(650 kilometers) wide but only about 2.5 miles (4 km) tall. It erupted for a
few million years during the early Cretaceous period, about 144 million years
ago, and has been extinct since then, the researchers report. [50 Amazing Volcano Facts]
Explaining ocean plateaus
Like other massive
volcanoes, Tamu Massif seems to have a central cone that spewed lava down its
broad, gentle slopes. The evidence comes from seismic surveys and lava samples
painstakingly collected over several years of surveys by research ships. The
seismic waves show lava flows dipping away from the summit of the volcano.
There appears to be a series of calderas at the summit, similar in shape to the
elongated and merged craters atop Mauna Loa, Sager said.
Until now,
geologists thought Tamu Massif was simply part of an oceanic plateau called Shatsky Rise in the northwest Pacific Ocean.
Oceanic plateaus are massive piles of lava whose origins are still a matter of
active scientific debate. Some researchers think plumes of magma from deep in
the mantle punch through the crust, flooding the surface with lava. Others
suggest pre-existing weaknesses in the crust, such as tectonic-plate
boundaries, provide passageways for magma from the mantle, the layer beneath
the crust. Shatsky Rise formed atop a triple junction, where three plates
pulled apart.
Tamu Massif's new
status as a single volcano could help constrain models of how oceanic plateaus
form, Sager said. "For anyone who wants to explain oceanic plateaus, we
have new constraints," he told LiveScience. "They have to be able to
explain this volcano forming in one spot and deliver this kind of magma supply
in a short time."
Sager said other,
bigger volcanoes could be awaiting discovery at other oceanic plateaus, such
as Ontong Java Plateau, located north of the Solomon Islands in the southwest
Pacific Ocean. "Structures that are under the ocean are really hard to
study," he said.
Floating volcano
Oceanic plateaus are the biggest piles of lava on Earth. The outpourings
have been linked to mass extinctions and climate change. The volume of Tamu
Massif alone is about 600,000 cubic miles (2.5 million cubic km). The entire
volcano is bigger than the British Isles or New Mexico.
Despite Tamu's
huge size, the ship surveys showed little evidence the volcano's top ever poked
above the sea. The world's biggest volcano has been hidden because it sits on
thin oceanic crust (orlithosphere), which can't
support its weight. Its top is about 6,500 feet (1,980 meters) below the ocean
surface today.
"In the case
of Shatsky Rise, it formed on virtually zero thickness lithosphere, so it's in
isostatic balance," Sager said. "It's basically floating all the
time, so the bulk of Tamu Massif is down in the mantle. The Hawaiian volcanoes
erupted onto thick lithosphere, so it's like they have a raft to hold on to.
They get up on top and push it down. And with Olympus Mons, it's like it formed
on a two-by-four."
Sager and his
colleagues have studied Shatsky Rise for decades, seeking to solve the puzzle
of oceanic plateaus. About 20 years ago, they named Tamu Massif after Texas
A&M University, Sager's former employer, he said.
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