Seismological study shows ancient lower mantle flow field under Philippine sea plate
2024-03-12
(Press-News.org)
Researchers from China and Japan have discovered distinct characteristics of the lower mantle flow field. They investigated seismic anisotropy in the upper part of the lower mantle beneath the Philippine Sea Plate (PSP) and found that the ancient lower mantle flow field is still preserved there.
The study was published in Nature Geoscience.
The lower mantle is an important layer of the Earth and may play an important role in the evolution and material cycling of Earth's interior. It is generally believed to be not only the final destination of subducted slabs, but also the birthplace of mantle plumes, which are two major styles in the evolution and material cycling of the Earth's surface and interior. However, our knowledge of the characteristics of the flow field and geodynamics of the lower mantle is still deficient.
In this study, the researchers performed P-wave azimuthal anisotropy tomography to image the 3D anisotropic structure of the crust and mantle down to a depth of 1,600 km beneath the PSP. The tomographic results show that N-S fast velocity directions (FVDs) exist at depths of 700–900 km below the mid-PSP. They also observed two isolated fast velocity anomalies with NW-SE FVDs at depths of 700–1,600 km beneath the PSP.
They found that the N-S FVDs at depths of 700–900 km are not related to the slab subduction, because they occur away from the present subduction zones. They are also independent of a mantle plume, as there has been no active mantle plume beneath the PSP since the early Cenozoic.
Based on previous geodynamic simulations and seismological results, the researchers inferred that the N-S FVDs at depths of 700–900 km reflect the remnant Pacific lower mantle flow field at about 50 Ma.
In addition, the two isolated fast velocity anomalies are consistent with seismic scatterers at depths of 1,000–1,800 km detected by previous seismological studies, and their locations are generally consistent with that of the spreading center between the Izanagi and Pacific plates when this spreading center was about to subduct beneath the Eurasian Plate. Thus, the isolated fast velocity anomalies are inferred to be remnants of the subducted Izanagi slab.
"The NW-SE FVDs in the two isolated fast anomalies are further inferred to reflect the Pacific lower mantle flow field at about 40 Ma, because the two isolated fast velocity anomalies are surrounded by amorphous mantle flow field and are not affected by the present lower mantle flow," said Prof. FAN Jianke from the Institute of Oceanology of the Chinese Academy of Sciences (IOCAS), first and corresponding author of the study.
"Our study shows that seismic anisotropy is more widespread in the lower mantle than previously thought," said Prof. FAN. "These observations also provide important and independent seismic evidence for the existence of past deformation in the lower mantle, which can help us better understand the geodynamic properties of the lower mantle."
This study was supported by the National Natural Science Foundation of China, the Strategic Priority Research Program of CAS, and the Japan Society for the Promotion of Science, etc.
END
ELSE PRESS RELEASES FROM THIS DATE:
2024-03-12
*EMBARGOED UNTIL TUESDAY, MARCH 12, AT 6 A.M. ET
Age-related changes that cause the skin to stiffen and become less elastic may also contribute to higher rates of metastatic skin cancer in older people, according to research by investigators from the Johns Hopkins Kimmel Cancer Center.
The study, published March 12 in Nature Aging, shows that increased stiffness in aging skin increases the release of a protein called ICAM1. Increased ICAM1 levels stimulate blood vessel growth in the tumor, helping it grow. It also makes the blood vessels “leaky,” enabling tumor cells ...
2024-03-12
Despite being scattered across more than a million square kilometres, new research has revealed that remote coral reefs across the Seychelles are closely related. Using genetic analyses and oceanographic modelling, researchers at Oxford University demonstrated for the first time that a network of ocean currents scatter significant numbers of larvae between these distant islands, acting as a ‘coral superhighway.’ These results are published today in Scientific Reports.
Dr April Burt (Department of Biology, University of Oxford, and Seychelles Islands Foundation), lead author of the study, said: ‘This discovery is very important because a key factor ...
2024-03-12
CAMBRIDGE, MA -- Tumors can carry mutations in hundreds of different genes, and each of those genes may be mutated in different ways — some mutations simply replace one DNA nucleotide with another, while others insert or delete larger sections of DNA.
Until now, there has been no way to quickly and easily screen each of those mutations in their natural setting to see what role they may play in the development, progression, and treatment response of a tumor. Using a variant of CRISPR genome-editing known as prime editing, MIT researchers have ...
2024-03-12
Rainforest seedlings are more likely to survive in natural forests than in places where logging has happened – even if tree restoration projects have taken place, new research shows.
Scientists monitored over 5,000 seedlings for a year and a half in North Borneo.
They studied a landscape containing both natural forest and areas logged 30 years ago – some of which were recovering naturally, while some had been restored by methods including tree planting.
A drought had triggered “mast fruiting” across ...
2024-03-12
More than 90% of the commercially available carotenoids are synthetically produced using chemicals. To meet the increasing demand for cost-effective natural compounds in carotenoid synthesis, researchers at Xiamen University, China, have developed an engineered S. cerevisiae yeast strain capable of selectively overproducing carotenoids. They redesigned the genomic sequence and critical pathways to optimize carotenoid production. This novel and successful research approach can be extended to other model ...
2024-03-12
When we recycle electronic devices we can no longer use, we expect to make the most out of the precious natural resources that went into building them. But electronic waste is notoriously difficult to recycle, because it’s hard to separate the different metals in the waste from each other. Scientists have now found a way of selectively capturing metals from a waste stream using spent brewer’s yeast, the same beer byproduct that goes into Marmite. Not only that: the yeast can be reused, making the process even more eco-friendly.
“Electronic waste is difficult to recycle because it is very heterogeneous,” said Dr Klemens Kremser ...
2024-03-12
Does previous experience bias a person in future estimations? Yes, Osaka Metropolitan University researchers in Japan report, but only if the person engages higher processing powers by responding, as opposed to simply observing.
They made their findings through experiments involving participants estimating the number of dots flashed on a screen. Participants either had to input their estimate before making another estimate on a new set of dots or were not prompted to do anything but observe. The researchers found ...
2024-03-12
11 March 2024, Singapore – A study[1] by KK Women’s and Children’s Hospital (KKH), Singapore General Hospital (SGH) and National University Hospital (NUH) has revealed that COVID-19 transmission from mothers to their newborns is low.
The study involving 371 women who had COVID-19 infection during pregnancy and their newborns found that only four infants or 1.1 per cent of the babies were diagnosed with COVID-19 after birth, of which three (1.1 per cent) were from mothers who were COVID-19 vaccinated and one infant (1.3 per cent) was from a mother who was not vaccinated.
Senior Author of the study, Dr Yeo Kee Thai, Senior Consultant, Department of Neonatology, KKH ...
2024-03-12
Despite the importance of biodiversity and the urgency to conserve it, assessing what aspect of biodiversity requires the highest priority has proven complex, especially when conservation resources are limited. A new study published in Current Biology sheds light on this question.
Prof. CHEN Zhiduan's team from the Institute of Botany of the Chinese Academy of Sciences (IBCAS) and international collaborators have identified the spatial heterogeneity of biodiversity hotspots and endemism centers. With ...
2024-03-12
Kyoto, Japan -- Cells possess an innate immune system that defends against invasive pathogens such as bacteria and viruses. Previous studies have mapped out the cytoplasmic cGAS-STING pathway in the cytoplasm, known for responding to foreign nucleic acids, such as double-stranded DNA.
Micronuclei -- or MN, abnormal intracellular structures containing the cell's DNA -- have also been suspected of triggering the pathway. However, no conclusive evidence exists of pathway activation by MN-induced cyclic GMP-AMP synthase, or cGAS.
Now, Kyoto University and the AIRC Institute of Molecular Oncology, or IFOM, have ...
LAST 30 PRESS RELEASES:
[Press-News.org] Seismological study shows ancient lower mantle flow field under Philippine sea plate
