Abstracts & Articles on the Natural Sciences

[JMcB]

Moon-forming impactor as a source of Earth’s basal mantle anomalies

Qian Yuan, Mingming Li, Steven J. Desch, Byeongkwan Ko, Hongping Deng, 
Edward J. Garnero, Travis S. J. Gabriel, Jacob A. Kegerreis, Yoshinori Miyazaki, Vincent Eke & Paul D. Asimow 


Abstract
Seismic images of Earth’s interior have revealed two continent-sized anomalies with low seismic velocities, known as the large low-velocity provinces (LLVPs), in the lowermost mantle. The LLVPs are often interpreted as intrinsically dense heterogeneities that are compositionally distinct from the surrounding mantle. Here we show that LLVPs may represent buried relics of Theia mantle material (TMM) that was preserved in proto-Earth’s mantle after the Moon-forming giant impact. Our canonical giant-impact simulations show that a fraction of Theia’s mantle could have been delivered to proto-Earth’s solid lower mantle. We find that TMM is intrinsically 2.0–3.5% denser than proto-Earth’s mantle based on models of Theia’s mantle and the observed higher FeO content of the Moon. Our mantle convection models show that dense TMM blobs with a size of tens of kilometres after the impact can later sink and accumulate into LLVP-like thermochemical piles atop Earth’s core and survive to the present day. The LLVPs may, thus, be a natural consequence of the Moon-forming giant impact. Because giant impacts are common at the end stages of planet accretion, similar mantle heterogeneities caused by impacts may also exist in the interiors of other planetary bodies.


https://www.nature.com/articles/s41586-023-06589-1




There is also an article on the subject here:

Scientists say they’ve finally found remnants of Theia, an ancient planet that collided with Earth to form the moon

JACKIE WATTLES CNN


Figure 3 … the anomalies viewed (a) from the North pole and (b) from the South pole. These plots emphasize the larger size of the African anomalies compared to the Pacific anomalies. Surface topography is projected onto the CMB for reference. See also the Supporting Information.




https://www.aol.com/news/collision-forme...16923.html

[CLTVTE]

Out of Tibet: Ancestral Woolly Rhino Suggests Origin of Ice Age Megaherbivores in High Plateau

http://english.ivpp.cas.cn/research/prog...68131.html

Among the most iconic Ice Age mammals, the woolly rhino (Coelodonta) was widespread in northern Eurasia and adapted to cold climates in the mammoth steppe during the late Pleistocene. The known fossil record suggests that the woolly rhino evolved in Asia, but its early ancestry remains elusive. The new middle Pliocene (~3.7 million years ago) woolly rhino, Coelodonta thibetana, from the high-altitude Zanda Basin at the foothill of the Himalayas in southwestern Tibet occupies the most basal position of the Coelodonta lineage and is the earliest representative of the genus. As the Ice Age began about 2.8 million years ago, the Tibetan woolly rhino descended, through intermediate forms, to low altitude, high latitude regions in northern Eurasia, and along with the Tibetan yak, argali, and bharal, became part of the emerging Mammuthus-Coelodonta fauna in the middle to late Pleistocene.

(Late Pleistocene ended 11700 years ago.)

[JMcB]

The 1831 CE mystery eruption identified as Zavaritskii caldera, Simushir Island (Kurils)

William Hutchison, Patrick Sugden, Andrea Burke, and Gill Plunkett

December 30, 2024



Significance

One of the largest volcanic eruptions of the nineteenth century took place in 1831 CE. Although this event led to significant Northern Hemisphere climate cooling, the source of this eruption remains a mystery. Using evidence from well-dated ice cores and stratigraphic records we pinpoint Zavaritskii caldera, an extremely remote volcano located in the Kuril Islands (between Japan and Kamchatka), as the source of this eruption. By reconstructing its magnitude and radiative forcing we show that Zavaritskii can account for the climate cooling in 1831–1833 CE. These data provide a compelling candidate for this large-magnitude mystery eruption and demonstrate the climate-changing potential of these remote yet highly significant Kuril Island volcanoes.



Abstract

Polar ice cores and historical records evidence a large-magnitude volcanic eruption in 1831 CE. This event was estimated to have injected ~13 Tg of sulfur (S) into the stratosphere which produced various atmospheric optical phenomena and led to Northern Hemisphere climate cooling of ~1 °C. The source of this volcanic event remains enigmatic, though one hypothesis has linked it to a modest phreatomagmatic eruption of Ferdinandea in the Strait of Sicily, which may have emitted additional S through magma–crust interactions with evaporite rocks. Here, we undertake a high-resolution multiproxy geochemical analysis of ice-core archives spanning the 1831 CE volcanic event. S isotopes confirm a major Northern Hemisphere stratospheric eruption but, importantly, rule out significant contributions from external evaporite S. In multiple ice cores, we identify cryptotephra layers of low K andesite-dacite glass shards occurring in summer 1831 CE and immediately prior to the stratospheric S fallout. This tephra matches the chemistry of the youngest Plinian eruption of Zavaritskii, a remote nested caldera on Simushir Island (Kurils). Radiocarbon ages confirm a recent (<300 y) eruption of Zavaritskii, and erupted volume estimates are consistent with a magnitude 5 to 6 event. The reconstructed radiative forcing of Zavaritskii (−2 ± 1 W m−2) is comparable to the 1991 CE Pinatubo eruption and can readily account for the climate cooling in 1831–1833 CE. These data provide compelling evidence that Zavaritskii was the source of the 1831 CE mystery eruption and solve a confounding case of multiple closely spaced observed and unobserved volcanic eruptions.


https://www.pnas.org/doi/10.1073/pnas.2416699122