According to new research, chemical leftovers from the very earliest days of our planet could still be present, and this could improve our understanding of plate tectonics.
The team behind the study compares these leftovers to clumps of flour at the bottom of a bowl of batter, which have not been properly mixed over the course of billions of years, which show up as anomalies on seismic wave readings.
Ultra-low velocity zones are where the waves slow to a crawl near the core of the Earth. Scientists think they may have found the answer to the big question of what these zones are made out of.
Surya Pachhai, seismologist from the Australian National University, says that the finding changes their view on the origin and dynamics of ultra-low velocity zones.
The type of ultra-low velocity zone can be explained by the creation of chemical Heterogeneities at the very beginning of the Earth's history, and they are still not well mixed after 4.5 billion years of mantle convection.
It's not easy to measure down through around 2,900 kilometers of rock to get a sense of the composition of the waves. The scientists used a reverse-engineering approach to run hundreds of thousands of computer simulations.
The team was able to narrow down the possibilities of what they could make by comparing the models to actual readings from underneath the Coral Sea.
The researchers suggest that iron oxide could be used to make the ULVZs, but that it could be made from other materials. It looks like this section of our planet is made up of several sublayers, something that has not been suspected before.
This could have been caused by a planetary object smashing into the early Earth. The event is thought to have thrown up debris that formed the Moon, and it's also likely to have created an ocean of magma, made up of rock, gases, and crystals, which could have sunk down to its current position over billions of years.
The thermal and chemical status of the Earth's lowermost mantle is an important part of mantle convection that drives plate tectonics, according to Pachhai.
The density of the waves goes up by a third, and they slow down by a half. It has been suggested that these areas of the mantle are partially melted and provide magma for volcanic hot spots on the surface.
Not all of the high density zones match up with volcanic activity, which suggests something else is going on. The research team used computer modeling to reveal the surprising layers that make up the Ulus.
The new research shows that the mantle and the ULVZs at the bottom of it can drive the movement of tectonic plates close to the surface, which means that we can learn more about the birth of the Earth, but also about how it's behaving today.
Michael Thorne from the University of Utah says that the ultra-low velocity zones are the most extreme features in the deep mantle.
These are some of the most extreme features on the planet.
The research has been published.
