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Palaeointensity of Australasian tektites from South China

Geophysical Journal International - Wed, 01/21/2026 - 00:00

SummaryPalaeomagnetic studies of impact glasses offer valuable insights into their magnetization processes and thermal histories associated with impact cratering events. Australasian tektites are broadly distributed in the largest and youngest strewn field of the Cenozoic, and they provide a unique opportunity to investigate the intensity of Earth’s magnetic field around 788 ka and potential impact-induced magnetic fields. The northern part of the Australasian strewn field covers South China, and it corresponds to the uprange zone of the impactor’s trajectory. Magnetic properties of Australasian tektites in South China may contain unique information about this impact event, but their palaeomagnetic characteristics remain poorly constrained. Here, we report the first palaeointensity data of Australasian tektites sampled from the Early-Middle Pleistocene strata in South China. The results show that Muong Nong-type tektites recorded palaeointensities of 30 ± 8 μT, consistent with the geomagnetic field intensity around 780–790 ka. These findings suggest that around 788 ka, Earth’s magnetic field had partially recovered from the earlier intensity decline associated with the precursor event of the Matuyama–Brunhes reversal. By contrast, the splash-form tektites in South China are characterized by extremely weak natural remanent magnetization and unstable magnetization components, posing challenges for deriving reliable palaeointensity data. Although strong impact-induced remanent magnetization was not detected in the samples, this study demonstrates that Australasian tektites, particularly Muong Nong-type, are well suited for palaeomagnetic studies that may reveal potential impact-induced magnetization.

Influences of Layered Heterogeneity on Poroelastic Behavior of Geological Reservoirs

Geophysical Journal International - Wed, 01/21/2026 - 00:00

SummaryFluid-rock interactions in geological reservoirs can influence pore pressure and induce ground deformation at rates from millimeters to centimeters per year. Elastic deformation models often simplify structural heterogeneity that controls pore pressure and strain distributions, leading to inaccurate interpretations of reservoir properties from geodetic data. Here we investigate how depth-varying rock hydromechanical properties affect the magnitude, rate, and spatiotemporal characteristics of poroelastic deformation and pore pressure. Motivated by the Salton Sea geothermal field, we develop finite-element models of multilayered reservoirs to assess their transient and steady-state behavior in single-well fluid-extraction scenarios. These cases include (1) caprock-reservoir systems with varying permeability and caprock thickness, (2) compaction-induced porosity variations following Athy’s law, and (3) depth-dependent Young’s modulus. While uniformly lower porosity or permeability produces higher rates and earlier onset of deformation and pore-pressure changes, a less permeable or thicker caprock reduces vertical surface displacements, with pressure change reversals near the surface. Young’s modulus varying in alternating or linear profiles generally produces larger vertical displacements and non-monotonic displacement rate histories due to cross-layer fluid migration. Regarding spatiotemporal patterns, porosity or permeability decreasing with depth, or a thicker caprock, accelerates radial expansion of the deformation signal. In contrast, only layered mechanical properties can substantially alter the initial crossover distance and peak-value ratio between the vertical and radial surface displacements, indicating distinct impacts on deformation signatures. Our findings highlight the importance of accounting for structural heterogeneity in predicting and inferring the evolution of poroelastic processes in reservoir systems.

Some creeks temporarily run stronger after wildfire, and now we know why

Phys.org: Earth science - Tue, 01/20/2026 - 21:31

New UBC Okanagan research shows that wildfire can change how much water remains in streams during the driest months of the year.

Q&A: Why Philly has so many sinkholes

Phys.org: Earth science - Tue, 01/20/2026 - 21:14

In early January, a giant sinkhole formed at an intersection in the West Oak Lane neighborhood of North Philadelphia after a water main break. Just two weeks earlier, the city reopened a section of the Schuylkill River Trail in Center City that had been shut down for two months due to a sinkhole. Last summer, some residents of Point Breeze in South Philly also waited two months for a sinkhole on their block to be repaired.

North Atlantic deep waters show slower renewal as ocean ventilation weakens

Phys.org: Earth science - Tue, 01/20/2026 - 21:11

The ocean is continuously ventilated when surface waters sink and transport, for example, oxygen and carbon to greater depths. The efficiency of this process can be estimated using the so-called water age, which describes the time elapsed since a water mass last was in contact with the atmosphere.

Get ready for smokier air: Record 2023 wildfire smoke marks long-term shift in North American air quality

Phys.org: Earth science - Tue, 01/20/2026 - 21:00

A new analysis of air quality data from the past 70 years shows that Canada's record wildfire smoke in 2023 is part of a broader, continent-wide trend toward smokier skies across North America.

Scientists plan deep-sea expedition to probe 'dark oxygen'

Phys.org: Earth science - Tue, 01/20/2026 - 20:48

A team of scientists announced Tuesday they have developed new deep-sea landers specifically to test their contentious discovery that metallic rocks at the bottom of the ocean are producing "dark oxygen".

Cleaner ship fuel linked to reduced lightning in key shipping lanes

Phys.org: Earth science - Tue, 01/20/2026 - 20:18

Cuts in sulfur emissions from oceangoing vessels have been tied to a reduction in lightning stroke density along heavily trafficked shipping routes in the Bay of Bengal and the South China Sea, according to new research from the University of Kansas.

Previously unknown chemical pathway for air pollution particle formation uncovered

Phys.org: Earth science - Tue, 01/20/2026 - 20:00

An atmospheric scientist at The University of Alabama in Huntsville (UAH), a part of The University of Alabama System, has helped uncover a previously unknown chemical pathway that plays a major role in the formation of air pollution particles in environments influenced by both natural and human-made emissions—an advance that could reshape how scientists understand air quality and climate impacts.