Published Tuesday, September 10th 2013 to 3:00
The largest volcano the world, of an area equivalent to the British Isles, would be buried since 145 million years under the waters of Pacific, to some 1500 km east the coast of Japan, reveals a study published Thursday.
We know less well marine that the surface of the Moon funds. Evidenced by a tapi under the Pacific Ocean volcanic monster. “It is a wide dome and rounded 450 km on 650 km», either a comparable to that surface “the Olympus Mons on the planet Mars» considered the largest volcano of any the solar system, underlines a study published in the British journal Nature Geoscience. Christened “Massif Tamu», the beast is tapie at heart of a chain of underwater mountains, Shatsky Rise, whose summit culminates to 3.5 km beneath the sea level and whose roots plunge some 30 km under the surface. And fortunately for les Terriens, it seems she either asleep since millions of years, indicates William Sager, oceanographer at the American University of Houston, who led the study. Shields. This volcanic training was long known geologists but these thought hitherto be dealing with a simple “mégavolcan” among an already identified dozen other “oceanic plateaus». These “mégavolcans», also found well to the surface of the earth qu’immergés at the bottom of seas, are so massifs with their millions of cubic kilometers of solidified lava that scientists generally consider it took several neighboring volcanoes uniting their strengths and coulees of magma to give them birth. This is the case by example for the volcanic edifice of the island of Hawaii, consists of five “volcanoes shields” distinct. It same goes for Iceland, composed of dozens of different volcanoes, some extinguished, other assets. But the analysis of samples and the structure of Massif Tamu in “gives a different image”, write William Sager, oceanographer at Texas A & M University, and his team. Even if systems associating several volcanoes displayed a size upper, “the Massif Tamu is the largest known in the world isolated volcano», they argue.
Cousins. According to these experts, it might even be the “elementary brick of a vast oceanic plateau, outcome of a single and unique jet» of molten rock which would have lasted few million years “only” at the very early Cretaceous. “Le Massif Tamu demonstrates that the enormous volcanoes found on other planets the solar system have cousins, here same on Earth. But the terrestrial variety of such volcanoes is poorly understood because these monsters have found a good place to hide: under the sea, “notes the study. D’other giants could therefore slumber far under the sea, escaping at the sight of scientists. “We do not have the necessary data for see inside and know their structure, but I would not be surprised we discovers that Tamu is not alone», declares Mr. Sager. “In fact, the largest oceanic plateau is the Ontong Java, in the equatorial Pacific, east Solomon Iles. And it is well larger than the Tamu, it fact the size of the France », either more than 500 000 km2, precise the researcher.
This volcano is tapi at heart of a chain of underwater mountains, Shatsky Rise, whose summit culminates to 3.5 km beneath the sea level
The belt of fire
The belt of fire Pacific account 452 volcanoes, ie 75% of volcanoes emerged of the planet, whether active or extinct. This concentration is explained by the subduction of oceanic plates (mainly Nazca plates, Cocos, Juan de Fuca and Pacific) under less dense plates (mainly south-American, caribbean, North American, Okhotsk, Filipino and Australian) . The subduction this is the process by which an oceanic tectonic plate curves and plunges under another before plate from sinking in the mantle. The game of these tectonic plates is also at the origin of frequent earthquakes (90% of earthquakes and 80% of the greatest tremors). The volcanoes of the belt fire Pacific are therefore mainly of volcanoes subduction, who organize themselves in continental volcanic arcs (chains or cordilleras volcanic) for the volcanoes of continental margin (America), or in island volcanic arcs. The belt of fire Pacific fact part of three most important of the planet zones of seismic activity, with the Mid-Atlantic dorsal and the Alpine belt.