Far beneath the floor of the Pacific Ocean, researchers have been able to identify what appear to be the remains of ancient oceanic crust, which could have sunk into the mantle 250 million years ago. This new discovery allows us to better understand the origin of some of the giant structures found at the base of the mantle.
This is done by studying the structure coatcoat Beneath the southeastern part of the Pacific Ocean, researchers realized there was something strange down there. In fact, data from seismic tomography, a technique that uses seismic waves produced by distant earthquakes to image the Earth's internal structure, revealed an unusual overthickness across the mantle transition zone. This, with a depth of between 410 and 660 km, represents the passage between the upper mantle and the lower mantle.
This transition zone corresponds to the depths at which olivine, the main mineral in the mantle, undergoes a rearrangement of its crystalline structure, due to the increase in pressurepressure. However, this phase change can be affected by temperature.
Remnants of very ancient oceanic crust
The additional thickness of the transition zone observed by scientists under the ridge East Pacific Rise Which indicates the presence of cold material in this region of the mantle. But whoever says cold matter says matter coming from the surface. The researchers believe they have identified the remains of ancient oceanic crust, which had long since sunk into the mantle. via A Subduction zoneSubduction zoneAt the time when the first dinosaurs appeared.
Data indicate that the age of this oceanic crust is 250 million years. However, it appears to have sunk into the mantle more slowly than previously thought. To scientists, this suggests that the transition zone acts as a brake, slowing the descent of material into the lower mantle.
Impact on deep mantle dynamics
The presence of this ancient oceanic crust in the mantle could also have implications for the dynamics of the entire region. In fact, the origin of the strange shape appears to be important abnormalityabnormality to speedspeed Which we observe at the base of the mantle, which we call the Pacific LLSVP (Large province with low shear speed))or com. superplumecom. superplume.
This study was published In the magazine Advancement of scienceIt shows the extent to which surface elements can influence the deep dynamics of the mantle.
