The new study led by the University of Cambridge is the first to obtain detailed ‘images’ of an unusual pocket of rock in the boundary layer with The core of the earthabout three thousand kilometers below the surface.
The mysterious rocky region, which lies almost directly below the Hawaiian Islands, is one of a number of regions with extremely low velocities – so-called because earthquake waves are slow to arrive as they pass through them.
The searchpublished year Nature Communicationsis the first to detail the intricate interior transformations of one of these pockets, shedding light on Earth’s deep interior landscape and the processes that operate within it.
Etna volcano eruption January 12, 2011. View from the East. Image credit: gnuckx qua FlickrPublic domain
“Of all the features inside the Earth, these are the most complex and fascinating. Now, we have the first solid evidence showing their internal structure – it’s a real milestone in deep-earth seismology,” said lead author Dr Zhi Li. student at Cambridge’s Department of Earth Sciences.
The Earth’s interior is layered like an onion: in the center is an iron-nickel core, surrounded by a thick layer called the mantle, and on top is the thin outer mantle – the crust that we living. Although the mantle is solid rock, it is hot enough to flow extremely slowly. These internal convection currents provide heat to the surface, fuel the movement of tectonic plates, and power volcanic eruptions.
Scientists use seismic waves from earthquakes to ‘see’ below the Earth’s surface – the echoes and shadows of these waves reveal a radar-like image of the terrain deep within. However, until recently, ‘images’ of structures at the core-mantle boundary, a key area of interest for studying heat flow inside our planet, have remained grainy and difficult to decipher. prefer.
The researchers used the latest numerical modeling methods to reveal kilometer-scale structures at the core-mantle boundary. According to co-author Dr Kuangdai Leng, who developed these methods at the University of Oxford, “We are really pushing the limits of modern high-performance computers for dynamic elastic simulations, take advantage of wave symmetries that have not been noticed or used before.” Leng, who now works at the Science and Technology Facility Council, says this means they can improve the resolution of images by orders of magnitude compared with previous work.
The researchers observed a 40% decrease in the speed of seismic waves traveling at the base of the ultra-low velocity region below Hawaii. This supports existing suggestions that the area contains much more iron than the surrounding rocks – meaning it is denser and more sluggish. Dr Sanne Cottaar from Cambridge Earth Sciences said: ‘It is possible that this iron-rich material is the remains of ancient rocks from the very beginning of the Earth, or even that iron could have leaked out of the core by a method. some undefined formula.
The study could also help scientists understand what lies beneath and creates chains of volcanoes like the Hawaiian Islands. Scientists have begun to notice a correlation between the positions of the described hot-spot volcanoes, including Hawaii and Iceland, and the extremely low-velocity regions at the bottom of the mantle. The origin of hotspot volcanism has been debated, but the most popular theory is that plume-like structures carry hot mantle material from the core-mantle boundary to the surface.
With images of the extremely low-velocity region below Hawaii now in hand, the team was also able to gather rare physical evidence from what could be the roots of the Hawaiian plume. Their observation of the dense, iron-rich rock beneath Hawaii will support surface observations. “Basalt rocks erupting from Hawaii have anomalous isotope signatures that could indicate early Earth origin or a leaky core, which means some dense material piled up at the site,” Cottaar said. the bottom has to be pulled to the surface,” Cottaar said.
Now it is necessary to capture more core-mantle boundaries to understand whether all the surface hotspots have a dense pocket of material at the bottom. Where and how the core-mantle boundary can be targeted depends on where the earthquake occurs and where seismometers are installed to record the waves.
The team’s observations add to growing evidence that Earth’s interior is just as varied as its surface. “These low-velocity regions are some of the most complex features we see at extreme depths – if we expand the search we can see an increasing level of complexity, both in terms of structure and structure and chemistry, at the core-mantle boundary,” says Li.
They now plan to apply their techniques to enhance the image resolution of other vesicles at the core-mantle boundary, as well as map new regions. Ultimately, they hope to map the geological landscape across the core-mantle boundary and understand its relationship to our planet’s dynamics and evolutionary history.
The source: University of Cambridge
