The Indian Ocean is residence to a mountain vary longer than the North American Rockies, and but at present, all 5,000 kilometers (3,107 miles) of it are hidden below the ocean.
A brand new examine delves deep beneath the waves to point out how the Ninetyeast Ridge was fashioned between 43 and 83 million years in the past – and its origins are fairly the shock.
Seamounts are underwater volcanoes present in each single ocean. They are brought on by ‘hotspots’ beneath Earth’s floor, by which gathering warmth melts away the mantle, releasing scorching plumes in a pipe-like upwelling.
At first, scientists didn’t suppose hotspots might transfer, so a path of volcanoes underwater was thought to consequence from tectonic plates sliding excessive of a stationary hotspot. Think of it like an upside-down stitching machine, with a stationary ‘needle’ of scorching materials piercing a fabric sliding above it, stitching a line.
As it seems, the Indian Ocean’s submerged volcanic chain was fashioned otherwise. The hotspot on this case is healthier imagined as a fountain pen, with the shifting ‘tip’ depositing liquid magma throughout the floor of the Earth.
“Unlike most volcanic hotspots that stay stationary within the mantle and create volcanic trails as tectonic plates drift over them, this examine discovered that the hotspot liable for the Ninetyeast Ridge moved by a number of hundred kilometres inside the mantle over time,” explains geoscientist Hugo Olierook from Curtin University in Australia.
“This sort of hotspot motion is regarded as frequent however is tough to show and has solely beforehand been demonstrated for just a few hotspots within the Pacific Ocean, making this the primary documented case within the Indian Ocean.”
The Kerguelen hotspot is the one liable for creating the Indian Ocean’s vertical underwater scar, and inconclusive research have advised the hotspot could have moved southward or westward over time.
Researchers in Australia, Sweden, China, and the US have now analyzed basalt samples from the Ninetyeast Ridge to assist that concept.
Their outcomes recommend that the Kerguelen mantle plume was created when the Indian Plate started to float northward, opening up the Indian Ocean.
If the Kerguelen hotspot had remained fastened under the Indian Plate throughout this motion, then the ridge would have moved northward on the similar charge because the seafloor spreading.
But that isn’t what the crew discovered.
Between 83 and 66 million years in the past, radioisotopic relationship suggests, the peaks of the mountain vary have been created at roughly half the speed of the seafloor spreading.
This means “the Kerguelen hotspot was not fastened beneath the Indian Plate,” writes the worldwide crew of researchers, led by Qiang Jiang from the China University of Petroleum.
It’s onerous to elucidate why the hotspot moved at this charge, however Jiang and colleagues argue “the most probably state of affairs is that the mantle plume was captured by the northward-migrating Indian-Antarctic spreading ridge, and plume supplies flowed repeatedly in the direction of the spreading ridge and erupted on the ridge.”
About 66 million years in the past, the plume was “disconnected” when the spreading ridge began drifting too distant. Later, the plume was briefly captured once more, this time by the western spreading ridge.
By roughly 42 million years in the past, the hotspot had drawn a vertical line that now separates the Indian Ocean into east and west.
“For years, tough age estimates of the Ninetyeast Ridge have been used to assemble fashions of how Earth’s tectonic plates moved and reconfigured,” says earth scientist Fred Jourdan from Curtin.
“By utilizing high-precision relationship we are able to refine these fashions considerably, main to higher insights into historic continental actions.”
The examine was printed in Nature Communications.
