The Indian Ocean is residence to a mountain vary longer than the North American Rockies, and but at the moment, all 5,000 kilometers (3,107 miles) of it are hidden beneath the ocean.
A brand new research delves deep beneath the waves to point out how the Ninetyeast Ridge was shaped 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’re brought on by ‘hotspots’ beneath Earth’s floor, through which gathering warmth melts away the mantle, releasing sizzling plumes in a pipe-like upwelling.
At first, scientists didn’t assume hotspots might transfer, so a path of volcanoes underwater was thought to consequence from tectonic plates sliding excessive of a stationary hotspot. Consider it like an upside-down stitching machine, with a stationary ‘needle’ of sizzling materials piercing a material sliding above it, stitching a line.
Because it seems, the Indian Ocean’s submerged volcanic chain was shaped another way. The hotspot on this case is best imagined as a fountain pen, with the transferring ‘tip’ depositing liquid magma throughout the floor of the Earth.
“Unlike most volcanic hotspots that remain stationary in the mantle and create volcanic trails as tectonic plates drift over them, this study found that the hotspot responsible for the Ninetyeast Ridge moved by several hundred kilometres within the mantle over time,” explains geoscientist Hugo Olierook from Curtin College in Australia.
“This kind of hotspot movement is thought to be common but is hard to prove and has only previously been demonstrated for a few hotspots in the Pacific Ocean, making this the first documented case in the Indian Ocean.”
The Kerguelen hotspot is the one answerable for creating the Indian Ocean’s vertical underwater scar, and inconclusive research have instructed 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 counsel 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 identical charge because the seafloor spreading.
However that isn’t what the workforce discovered.
Between 83 and 66 million years in the past, radioisotopic relationship suggests, the peaks of the mountain vary had been created at roughly half the speed of the seafloor spreading.
This implies “the Kerguelen hotspot was not fixed beneath the Indian Plate,” writes the worldwide workforce of researchers, led by Qiang Jiang from the China College of Petroleum.
It is onerous to elucidate why the hotspot moved at this charge, however Jiang and colleagues argue “the most likely scenario is that the mantle plume was captured by the northward-migrating Indian-Antarctic spreading ridge, and plume materials flowed continuously towards the spreading ridge and erupted at 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, rough age estimates of the Ninetyeast Ridge have been used to construct models of how Earth’s tectonic plates moved and reconfigured,” says earth scientist Fred Jourdan from Curtin.
“By using high-precision dating we can refine these models significantly, leading to better insights into ancient continental movements.”
The research was printed in Nature Communications.
