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Ultrafast studies of elusive chemical reactions in the gas phase

Science - Fri, 08/09/2024 - 07:00

Science, Volume 385, Issue 6709, August 2024.

Facilitating code peer review

Nature Geoscience - Fri, 08/09/2024 - 00:00

Nature Geoscience, Published online: 09 August 2024; doi:10.1038/s41561-024-01523-0

Authors can now choose to use Code Ocean upon submission to make the peer review of code easier.

The problem with dolomite

Nature Geoscience - Fri, 08/09/2024 - 00:00

Nature Geoscience, Published online: 09 August 2024; doi:10.1038/s41561-024-01490-6

The formation of dolomite eluded mineralogists for years. Jennifer Roberts explains why ‘the dolomite problem’ matters, and how it may now be closer to resolution.

Multifaceted aerosol effects on precipitation

Nature Geoscience - Fri, 08/09/2024 - 00:00

Nature Geoscience, Published online: 09 August 2024; doi:10.1038/s41561-024-01482-6

A consensus is emerging regarding the influence of aerosols on global precipitation patterns, although smaller-scale effects remain uncertain, according to a synthesis of recent work.

Multi-Mode Ambient Noise Double Beamforming Tomography with a Dense Linear Array: Revealing Accretionary Wedge Architecture across Central Taiwan

Geophysical Journal International - Fri, 08/09/2024 - 00:00

SummaryTaiwan, one of the most active orogenic belts in the world, undergoes orogenic processes that can be elucidated by the doubly-vergent wedge model, explaining the extensive island-wide geological deformation. To provide a clearer depiction of its cross-island orogenic architecture, we apply ambient noise tomography across an east-west linear seismic array in central Taiwan, constructing the first high-resolution 2-D shear velocity model of the upper crust in the region. We observe robust fundamental- and higher-mode Rayleigh waves, with the latter being mainly present in the western Coastal Plain. We develop a multi-mode double beamforming method to determine local phase velocities across the array between 2 and 5-sec periods. For each location, we jointly invert all available fundamental- and higher-mode phase velocities using a Bayesian-based inversion method to obtain a 1-D model. All 1-D models are then combined to form a final 2-D model from the surface to ∼10 km depth. Our newly developed 2-D model clearly delineates major structural boundaries and fault geometries across central Taiwan, thereby corroborating the previously proposed pro-wedge and retro-wedge models while offering insight into regional seismic hazards.

Thermal rock magnetic cycling (TRMC): a method to track Thermal alteration details for palaeointensity interpretations

Geophysical Journal International - Fri, 08/09/2024 - 00:00

SummaryAccurate absolute palaeointensity is essential for understanding dynamo processes on the Earth and other planetary bodies. Although great efforts have been made to propose techniques to obtain magnetic field strength from rock samples, such as Thellier-series methods, the amount of high-fidelity palaeointensities remains limited. One primary reason for this is the thermal alteration of samples that pervasively occurred during palaeointensity experiments. In this study, we developed a comprehensive rock magnetic experiment, termed thermal rock magnetic cycling (TRMC), that can utilize measurements of critical rock magnetic properties at elevated temperatures during multiple heating-cooling cycles to track thermal changes in bulk samples and individual magnetic components with different Curie temperatures in samples for palaeointensity interpretations. We demonstrate this method on a Galapagos lava sample, GA 84.6. The results for this specimen revealed that GA 84.6v underwent thermophysical alteration throughout the TRMC experiment, resulting in changes in its remanence carrying capacity. These findings were then used to interpret the palaeointensity results of specimen GA 84.6c, which revealed that the two-slope Arai plot yielded two linear segments with distinct palaeointensity values that were both biased by thermophysical alteration. To further test the TRMC method, we selected another historical lava sample (HS 2) from Mt. Lassen, detecting slight thermal-physical changes after heating the specimen HS 2–8C to a target temperature of 400° C. We also isolated a stable magnetic component with a Curie temperature below 400° C using the TRMC method, which may provide a more reliable palaeointensity estimate of 51 μT. By providing a method for tracking thermal alteration independent of palaeointensity experiments, the TRMC method can explore subtle, unrecognizable thermal alteration processes in less detailed palaeointensity measurements, which can help to assess the thermal stability of the measured samples and interpret the changes in the TRM unblocking spectrum and palaeointensity estimates, facilitating the acquisition of more reliable records for constrain the formation of the inner core and the evolution of Earth's magnetic field.

Researchers find unexpectedly large methane source in overlooked landscape

Phys.org: Earth science - Thu, 08/08/2024 - 20:34

When Katey Walter Anthony heard rumors of methane, a potent greenhouse gas, ballooning under the lawns of fellow Fairbanks residents, she nearly didn't believe it.

Tracking the restorative effects of good fire

Phys.org: Earth science - Thu, 08/08/2024 - 20:27

A few miles south of Yosemite's famed Glacier Point, ringed by striking granite domes, lies the Illilouette Basin. This small stretch of the Sierra Nevada Mountains has become a sort of fire laboratory, a place where natural wildfires have been allowed to burn since 1972. In contrast with the long-supported program of fire suppression that has dominated American forests since the late 19th century, resulting in dense and unhealthy forests, the Illilouette Basin's story is about the benefits that natural fire can bring to the landscape.