If we ever find yourself on a resting submarine float by a northeastern Indian Ocean, be on a surveillance for some extraordinary views: some-more than 50 vast seamounts, or underwater mountains, dot a sea floor, some rising as high as 3 miles (4,500 meters).
The Christmas Island Seamount Province, as a area is known, spans a 417,000-square-mile (1 million block kilometers) swath of seafloor.
Just how a large underwater structures got there has been adult for debate, though some new geochemical investigator work might have solved a mystery.
The seamounts are done of recycled rocks from a , pronounced geochemist Kaj Hoernle of a University of Kiel in Germany. Their violent geological story explains a large distance and obscure sequence of these features.
Ubiquitous and mysterious
Tens of thousands of seamounts line a floors of , though accurately how many of these shaped is unclear.
Some, like a Hawaiianâ€"Emperor seamount sequence that extends northwest from a Hawaiian Islands, , only as a islands themselves did. Other seamount bondage were combined when tectonic image bounds and other fractures in a sea membrane authorised lava to shun and harden during a surface.
But a Christmas Island Seamount Province doesn't fit possibly of these models, Hoernle said. The structures are too widespread and disband to have shaped over a singular hotspot; they’re also aligned perpendicularly along breaks in a sea crust, that means they didn't form above a fracture.
"We knew they were volcanic," Hoernle told OurAmazingPlanet, "but over that, it was some-more or reduction a mystery."
Geochemistry to a rescue
To solve a puzzle, Hoernle and his colleagues set out to map and collect samples of a seamounts.
The justification they brought behind to a lab told an engaging story: The rocks' geochemical signatures didn't compare those from mid-ocean ridges or . Instead, they matched a signatures of continental rocks â€" in particular, rocks from northwestern Australia.
Using this idea and tectonic image reconstructions, Hoernle's group traced a rocks behind to a ancient supercontinent of Gondwana.
Around 150 million years ago, larger India, Australia and Burma â€" all once partial of this supercontinent â€" began to difference pided from any other. This combined a swelling core (or mid-ocean ridge) that eventually shaped a Indian Ocean. As this was happening, a bottom partial of a continental membrane delaminated, or "peeled off in a sheet," Hoernle said.
The peeled-off continental , exhilarated adult and eventually was pulled to a aspect again during a Indian Ocean swelling center.
"When a swelling core upheld over that area, it radically sucked a continental pieces and pieces adult again," Hoernle said. "Because these pieces have some-more flighty calm [such as H2O and CO dioxide], they constructed some-more melted element than a normal top mantle, and shaped seamounts instead of a normal sea crust."
The initial seamount in a Christmas Island Province shaped around 136 million years ago. The swelling core continued to emanate seamounts until about 47 million years ago, when it migrated pided from a partial of a layer containing a recycled continental crust, Hoernle said.
The team's commentary are minute in a Dec emanate of a biography Nature Geoscience.
This story was supposing by , a sister site to LiveScience.
News referensi http://news.yahoo.com/surprising-christmas-island-seamounts-mystery-solved-144803227.html
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