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Earth of fire

Actualité volcanique, Article de fond sur étude de volcan, tectonique, récits et photos de voyage

Publié le par Bernard Duyck
Publié dans : #Actualités volcaniques
Image 3 D of the Tamu massif - Doc. Schmidt Ocean Institute

Image 3 D of the Tamu massif - Doc. Schmidt Ocean Institute

Located 1600 kilometers east of Japan in the Shatsky Rise, Tamu Massif deserves its title of largest terrestrial volcano : with 450 km x 650 km, or fifty times bigger than Mauna Loa in Hawaii - considered the largest active volcano - this massive rises to 2,000 meters below the sea level.

It was explored by dozens of ocean shipping in the past half century. Tamu owes its name to the Texas A & M. University who studies the volcano for decades.

Tamu is the largest volcano on Earth - its imprint can rival with that of the Martian giant Olympus Mons - Doc. Nature in 2013.

Tamu is the largest volcano on Earth - its imprint can rival with that of the Martian giant Olympus Mons - Doc. Nature in 2013.

The expedition in 2015 aboard the R / V Falkor Schmidt Institute of Oceanography, with the aim of mapping the magnetic field of Tamu, covered an area of ​​almost one million square kilometers, in 477 hours of observations, and 1.7 million measures of the magnetic field.

After thirty-six days brawl against sharks that attacked the equipment, a new 3D bathymetric map was made, providing a clearer view of this submarine volcano, although it must still be refined after analyzing the data collected.
 

A t-shirt, design for members of the scientific expedition and the crew of Falkor, was created by the Dr.Sager - Credit: Dr. William Sager

A t-shirt, design for members of the scientific expedition and the crew of Falkor, was created by the Dr.Sager - Credit: Dr. William Sager

Brief summary of previous studies on the Shatsky Rise :

The Shatsky Rise is a large oceanic plateau of 480,000 km², formed there 130-145 millions years, spanning over 1700 km. and consists of three main massifs: Shirshov, Ori, and Tamu; the latest is the oldest.

The Shatsky Rise, the oldest existing oceanic plateau, formed by a magmatic pulse at the intersection of a hotspot of triple junction, between the late Jurassic and early Cretaceous. (Nakanishi et al. 1989)

This formation is concomitant with a jump of 800 km. east of the triple junction Pacific-Izanagi-Farallon, and the reorganization of the Pacific-Izanagi ridge, which were probably made possible by the eruption of Shatsky Rise. (Sager et al. 1999).

 

Reconstruction of the Shatsky Rise position in the Pacific Ocean over time - according to McNutt and Fischer (1987) and RL Larson (2000) / in Ocean Drilling Program

Reconstruction of the Shatsky Rise position in the Pacific Ocean over time - according to McNutt and Fischer (1987) and RL Larson (2000) / in Ocean Drilling Program

Tectonic history of Shatsky Rise, illustrating the migration of ridges and triple junction (TJ) during formation of the rise. Dark magnetic lineations existed on the Pacific plate at the time given for each panel. Red lines = ridges, light purple lines = future isochrons, blue arrows = path of triple junction, yellow arrows = jumps and changes in direction (modified from Nakanishi et al., 1999).

Tectonic history of Shatsky Rise, illustrating the migration of ridges and triple junction (TJ) during formation of the rise. Dark magnetic lineations existed on the Pacific plate at the time given for each panel. Red lines = ridges, light purple lines = future isochrons, blue arrows = path of triple junction, yellow arrows = jumps and changes in direction (modified from Nakanishi et al., 1999).

Shatsky Rise mapping conducted during shipping 324 of the IODP

Shatsky Rise mapping conducted during shipping 324 of the IODP

Initial results :

According to William Sager, a geologist from the University of Houston and leader of the expedition, the western edge of Tamu Massif could be considered formed at a different time from the rest of the main body.

The entire massif is dotted with craters and cliffs. Many canyons that cut the sedimentary cover  and escarpments / cliffs on the west side of the massif
, probably formed by landslides, were identified.

Magnetic analysis provides a first impression on the fast genesis of massive, there are about 145 million years : a part of the volcano exhibits bands with different magnetic properties, which suggest regular outings of lava along the intersection of three mid-ocean ridges over time and reveal changes in polarity of Earth's magnetic field, while the other part is more difficult to explain ... a theory involves a large mantle plume that would have contributed to a heat supply and matter.

New 3D image structures of Tamu Massif, including a long cliff - Doc. Schmidt Ocean Institute.

New 3D image structures of Tamu Massif, including a long cliff - Doc. Schmidt Ocean Institute.

Data analysis continues and Dr. Sager hopes that a summary will explain the mystery, and at the same time that of a dozen similar structure on the ocean floor, and provide a better understanding of plate tectonics and their evolution .

 

Sources :

- National Geographic - Scientists Are Mapping the World's Largest Volcano / An expedition to Tamu Massif in the Pacific Ocean finds some surprises. – link

- AGU Blogosphere – Tamu massif : closing thougts from Chief Scientist Dr. W.Sager - link

- Nature - Underwater volcano is Earth's biggest / Tamu Massif rivals the size of Olympus Mons on Mars. - link

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