A joint UK research project recently published a study of one of the least known or understood parts of the Earth’s interior, the core-mantle boundary. By focusing their work on a large mantle plume under-neath Hawaiian archipelago, they have made some interesting observations about most enigmatic parts of Earth’s geological system.
New imaging techniques have enabled the team able to gain valuable information about this ultra low-velocity zone, which lies some 3,000 km (1,864 miles) below the surface of earth.
Until now, we knew this area existed by analyzing seismic waves that flow through planet. The name of the zone(s) comes from the way seismic waves slow down as they pass through them.
So far now, it’s been difficult to make them much more meaningful beyond some grainy, hard-to-analyze images. However, this new study of the mantle below Hawaii has produced some much clearer & higher-resolution images.
“Of all the features of the Earth’s deep interior, these are the most fascinating & complex,” says geophysicist Zhi Li from University of Cambridge in UK and a contributor to study.
“We now have the first solid evidence showing their internal structure – it’s a real milestone in deep Earth seismology,” he added.
To capture the images, the team developed new computational models that take high-frequency signals from the study area to create an understandable image. Use of this technique is able to produce a kilometer-scale look at rock pocket at resolutions magnitudes better than using conventional techniques.
It is now hoped that this technique can be used to probe the boundary between the Earth’s nickel-iron core and the surrounding mantle to better understand one of the major engines for plate tectonics, the formation of volcanoes and other related processes such as earthquakes.
It is now believed that the extra iron in these unusual zones could create the extra density shown in seismic wave patterns. Whether correct or not, studying this region is a top priority for some geologists.
“It is possible that this iron-rich material is a remnant of ancient rocks from early Earth’s history, or even that iron might-be leaking from the core by unknown means,” says seismologist Sanne Cottaar from University of Cambridge.
Possible link between ultra-low velocity zones and volcanic hotspots
Other scientists also believe there is a connection between ultra low velocity zones & volcanic hotspots like those in Hawaii & Iceland. One hypothesis is that these hotspots could be caused by material shooting-up from the core to the surface, termed “mantle hotspots”.
This new technique could also help revolutionize this field of study. Now, however, others can better focus on lava effusions that sit above hotspots to look for evidence of so-called “core leaking.”
While the use of seismic data from ultra-low-velocity zone is somewhat limited by where earthquakes occur and where seismographs are installed, the team is keen to apply their high-resolution image enhancements to other deep-earth locations.
“We’re really pushing the limits of modern high-performance computing for elastodynamic simulations by taking advantage of wave symmetries that haven’t been noticed or unused before,” says data scientist Kuangdai Leng from University of Oxford in UK.
