The Tamu massif , a rival for the Martian giants.

Earth's largest volcano , called " Tamu massif " lurks in the heart of Shatsky Rise , an underwater mountain range , located 1600 km east of Japan.

Her measurements likely rank in the second place of the largest volcanoes known in the solar system, after Olympus Mons on Mars : 450 km x 650 km . - a volume of 2.5 million cubic kilometers , and its summit is 3,500 m. below the sea level and its roots some 30 km . beneath the surface , hiding its mass (see cut in Physorg ) .

To fix the ideas , Hawaii consists of five separate shield volcanoes; the Mauna Loa, considered as the biggest active volcano, is 60 times smaller than the Tamu .

It owes its name , Tamu , at Texas A & M. University, who studies for twenty years.
 
 A 3D view and profile (in black ) of Tamu Massif , the largest volcano in the world . - Doc. MSN News
Shatsky Rise , surrounding magnetic lineations and fracture zones (heavy red lines ; Nakanishi et al. , 1999) Expedition 324 drill site ( red dots ) and ODP Site 1213 ( blue dot) . Dark area at lower right shows the basal outline of Olympus Mons (Mars) at the same scale . Inset shows the;rental of Shatsky Rise relative to Japan . - doc . LiveScience

The Shatsky Rise is a large oceanic plateau of 480,000 km² formed there are 130 to 145 million years , spanning 1700 km., composed of three main massive : Shirshov, Ori, and Tamu, the latter is the oldest .

The oldest existing oceanic plateau , the Shatsky Rise, is formed by magmatic pulse at the intersection of a hot spot of triple junction between the late Jurassic and early Cretaceous . ( Nakanishi et al 1989. ) Such formation is concomitant with a jump of 800 km. to the east of the triple junction Pacific - Farallon - Izanagi , and the reorganization of the Pacific - Izanagi ridge , which were probably made ​​possible by the eruption of Shatsky Rise . (Sager et al. 1999 )
 Reconstitution of  the position of the Shatsky Rise in the Pacific Ocean over time - from McNutt and Fischer ( 1987) and RL Larson ( 2000) / in Ocean Drilling Program

So far , we did not know if the Tamu Massif was one single volcano, or a composite volcano formed by several points of eruptions .

By integrating various sources, including drill core and data recorded by the IODP (Integrated Ocean Drilling Program ) in 2009 and seismic reflection data of 2010 and 2012 , the authors of the Nature Geosciences ( the team of Dr. Sager includes researchers from the Universities of Oregon, Yale , Hawaii and the United Kingdom ) confirm that the volume of basalt forming the Tamu Massif comes from a single source near its center.

Low and extended form of the massif means that the lava issued here have had to move on much longer distances than in other terrestrial volcanoes. Other, underwater volcanoes, or seamounts, punctuated by thousands the seafloor, but remain small and steep compared to the  Tamu massif (see 3D view above) .

Its shape differs from those of all other submarine volcanoes found on Earth, and may provide clues to the formation of other megavolcans, that can be found on other oceanic plateaus such as the Ontong Java Plateau in the South Pacific .

Sources :

- Physorg - Scientists confirm existence of largest single volcano on earth - link

- Live Science - Largest volcano on earth lurks beneath Pacific ocean - link

- IODP Expedition 324: Ocean Drilling at Shatsky Rise Gives Clues about Oceanic Plateau Formation - by William W. Sager, Takashi Sano, Jörg Geldmacher, and the IODP Expedition 324 Scientists - link

- Ocean Drilling Program - Extreme warmth in the Cretaceous and Paleogene: a depth transect on shatsky rise, Central Pacific - link