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Located about 1,000 miles east of Japan, Tamu Massif is the largest feature of Shatsky Rise, an underwater mountain range formed 130 to 145 million years ago by the eruption of several underwater volcanoes. Until now, it was unclear whether Tamu Massif was a single volcano, or a composite of many eruption points.
Credit: Image courtesy Integrated Ocean Drilling Program/U.S. Implementing Organization [IODP-USIO]
Tamu Massif stands out among underwater volcanoes not just for its size, but also its shape. It is low and broad, meaning that the erupted lava flows must have traveled long distances compared to most other volcanoes on Earth. The seafloor is dotted with thousands of underwater volcanoes, or seamounts, most of which are small and steep compared to the low, broad expanse of Tamu Massif.
Credit: Image courtesy Integrated Ocean Drilling Program/U.S. Implementing Organization [IODP-USIO]
“It’s not high, but very wide, so the flank slopes are very gradual,” Sager said. “In fact, if you were standing on its flank, you would have trouble telling which way is downhill. We know that it is a single immense volcano constructed from massive lava flows that emanated from the center of the volcano to form a broad, shield-like shape. Before now, we didn’t know this because oceanic plateaus are huge features hidden beneath the sea. They have found a good place to hide.”
Tamu Massif covers an area of about 120,000 square miles. By comparison, Hawaii’s Mauna Loa – the largest active volcano on Earth – is approximately 2,000 square miles, or roughly 2 percent the size of Tamu Massif. To find a worthy comparison, one must look skyward to the planet Mars, home to Olympus Mons. That giant volcano, which is visible on a clear night with a good backyard telescope, is only about 25 percent larger by volume than Tamu Massif.
Olympus Mons (Latin for Mount Olympus) is a large shield volcano on the planet Mars.
Credit: NASA
The study relies on two distinct, yet complementary, sources of evidence – core samples collected on Integrated Ocean Drilling Program (IODP) Expedition 324 (Shatsky Rise Formation) in 2009, and seismic reflection data gathered on two separate expeditions of the R/V Marcus G. Langseth in 2010 and 2012. The core samples, drilled from several locations on Tamu Massif, showed that thick lava flows (up to 75 feet thick), characterize this volcano. Seismic data from the R/V Langseth cruises revealed the structure of the volcano, confirming that the lava flows emanated from its summit and flowed hundreds of miles downhill into the adjacent basins.
According to Sager, Tamu Massif is believed to be about 145 million years old, and it became inactive within a few million years after it was formed. Its top lies about 6,500 feet below the ocean surface, while much of its base is believed to be in waters that are almost four miles deep.
“It’s shape is different from any other sub-marine volcano found on Earth, and it’s very possible it can give us some clues about how massive volcanoes can form,” Sager said. “An immense amount of magma came from the center, and this magma had to have come from the Earth’s mantle. So this is important information for geologists trying to understand how the Earth’s interior works.”
Mauna Loa had been called the largest volcano on Earth in volume and area covered.
Credit: USGS
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Contacts and sources:
Lisa Merkl
University of Houston
Is that where governments draw “red line” and bomb Mars because of it to be politically correct of an underground volcano that big could be racist.??
They already bombed the moon for being racist and not allowing illegal immigrants to live there
Nice job! It is so nice to discover science is alive and well in some disciplines. http://coldwarwarrior.com/