The coastline of Southeast Greenland is uplifting more rapidly than other parts of the island. This is caused by weak rocks beneath this part of Greenland, combined with the melting of the ice sheet, according to researchers.
Author(s): S. Werbowy, B. Pranszke, and L. Windholz
Studies of the static Stark effect are reported for the multiplets at 615.8, 645.6, 777.6, 822.4, 844.9, and 926.5 nm (vacuum wavelengths) of atomic oxygen, which are important for various applications. From the Stark patterns recorded at very high electric fields up to 780 kV/cm, we have determined…
[Phys. Rev. E 111, 025209] Published Thu Feb 27, 2025
The Fraser River is unique among the world's great rivers—a huge, relatively natural, undammed, mountain river running through a dense urban area.
Askoa Ibisate, a geographer specializing in fluvial geomorphology, has analyzed how the disappearance of the Olloki dam affects sediment transport. Ibisate concluded that the volume of pebbles mobilized by the demolition has increased, and their journey has been extended. The results are particularly significant because the monitoring work has been ongoing for seven years and the authorities are provided with valuable information for predicting the consequences of dam demolition. The work is published in the journal Geomorphology.
Publication date: Available online 15 February 2025
Source: Advances in Space Research
Author(s): Vladimir A. Srećković, Ljubinko M. Ignjatović, Milan S. Dimitrijević, Veljko Vujčić, Sanja Tošić, Felix Iacob
Earthquakes occur along fault lines between continental plates, where one plate is diving beneath another. Pressure builds between each plate, called fault stress. When this stress builds enough to release, the plates slip and grind against each other, causing an earthquake.
The nightmare scenario of Atlantic Ocean currents collapsing, with weather running amok and putting Europe in a deep freeze, looks unlikely this century, a new study concludes.
Imagine floating in space, gazing on a frozen white orb. The ball hangs in the void, lonely and gleaming in the light from its star. From pole to equator, the sphere is covered in a thick crust of ice. In orbit around the white planet is a single cratered moon.
A century of fire suppression, combined with global warming and drought, has led to increasingly destructive wildfires in the Western United States. Forest managers use tools like prescribed burns, thinning, mastication, and piling and burning to reduce fuel—live and dead trees, needles and leaves, and downed branches—that can feed intense wildfires. These methods aim to lower fuel levels, reduce crown density, and protect fire-resistant trees, fostering healthier, more resilient forests.
A new tool created using AI could help forecast volcanic eruptions around the world, following breakthrough research from a University of Canterbury-led team. The data-driven models developed by the team could become part of early warning systems used to predict future eruptions, with the potential to save lives and prevent damage to critical infrastructure.
Researchers from Japan and Taiwan reveal for the first time that helium, usually considered chemically inert, can bond with iron under high pressures. They used a laser-heated diamond anvil cell to find this, and the discovery suggests there could be huge amounts of helium in the Earth's core. This could challenge long-standing ideas about the planet's internal structure and history, and may even reveal details of the nebula our solar system coalesced from.
SummarySeismic anisotropy can inform us about convective flow in the mantle. Shear waves traveling through azimuthally anisotropic regions split into fast and slow pulses, and measuring the resulting shear-wave splitting provides some of the most direct insights into Earth’s interior dynamics. Shear-wave splitting is a constraint for path-averaged azimuthal anisotropy and is often studied regionally. Global compilations of these measurements also exist. Such compilations include measurements obtained using different data processing methodologies (e.g., filtering), which do not necessarily yield identical results, and reproducing a number of studies can be challenging given that not all provide the required information, e.g., about the source location. Here, we automatically determine SKS, SKKS and PKS shear-wave splitting parameters from a global dataset. This dataset includes all earthquakes with magnitudes ≥5.9 from 2000 to the present, collected from 24 data centers, totaling over 4,700 events and 16 million three-component seismograms. We obtain approximately 90,000 robust measurements for “fast azimuth”, φ, and delay time, δt, and 210,000 robust null measurements. Results generally agree with previous work but our measurements allow us to identify hundreds of “null stations” below which the mantle appears effectively isotropic with respect to azimuthal anisotropy, which are important for some splitting techniques. We make all measurements publicly available as a data product, along with detailed metadata. This serves two purposes: ensuring full reproducibility of results and providing all necessary information for future systematic use of our measurements, in tomography applications or comparisons with geodynamic flow predictions.
New Curtin University research has revealed how massive ancient glaciers acted like giant bulldozers, reshaping Earth's surface and paving the way for complex life to flourish.
The Walker circulation, an atmospheric circulation pattern in the tropics, has accelerated in recent years, puzzling climate scientists who had anticipated the opposite. Researchers from the Max Planck Institute for Meteorology and the University of Tokyo have found out why by revealing the competing effects between global warming and the sea surface temperature pattern effect.
Turbidity currents are an important natural process that often goes unnoticed: these powerful currents beneath the ocean surface carve deep submarine canyons, create huge sediment deposits and can damage submarine cables and pipelines. Although the phenomenon has been known for about 100 years, its high-energy nature has made it almost impossible to measure directly—any instruments placed in its path would be destroyed by its immense force, much like avalanches on land.
Long after tectonic plate movement has created mountains, forces such as weather and river erosion can continue to shape a landscape. One such landscape is the Colorado Plateau, which spans more than 336,000 square kilometers (83 million acres) across four states and encompasses iconic sites such as the Grand Canyon and Arches National Park.
Deep beneath the barren landscape of Antarctica lies secrets to the climatic history of the world. Frozen in the ice are chemical markers which, when studied by scientists, can help reveal a historical record of key climate events.
Abstract
To meet the high-precision and high-integrity positioning demands of safety–critical applications, monitoring the quality of precise satellite products in global navigation satellite system (GNSS) precise point positioning (PPP) is crucial. This work employs ionosphere-free (IF) PPP with ambiguity resolution (PPP-AR) phase residuals to construct test statistics for monitoring the quality of precise satellite corrections. By utilizing precise satellite orbit and clock products from CODE, WUM, and GRG, the PPP-AR phase residuals were first analyzed with sample moments, Allan variance and power spectral density (PSD). The key findings are as follows: (1) The skewness and kurtosis results indicate that ambiguity-fixed phase residuals deviate from an ideal zero-mean Gaussian distribution and exhibit a super-Gaussian distribution. (2) Allan variance and PSD analysis reveal that flicker noise dominates the phase residuals. (3) The noise amplitudes are similar for all satellites, but certain differences are observed among different GNSS systems and satellite types. (4) The noise level of phase residuals is influenced by the receiver types, antenna types, and precise products from different analysis centers. Leveraging the error characteristics, the two-step Gaussian overbounding (OB) method was employed to estimate the corresponding OB parameters of the phase residuals. The overbounding results demonstrate that, under similar conditions, phase residuals can be bounded by the calculated bound within the acceptable integrity risk after removing the detected outliers. Anomaly monitoring experiments further show that phase residuals can effectively capture anomalies in precise satellite corrections, with the set threshold successfully detecting such anomalies.
SummaryLove (LQ) and Rayleigh-wave (LR) dispersion data provide essential constraints on radially-anisotropic shear-wave velocity structure. Vertically-polarized S-wave velocity ($\rm S_V$) structure of India–Tibet are available from modeling of LR dispersion data, but reliable LQ dispersion measurements are limited. This is due to poor signal-to-noise (SNR) ratio on horizontal component waveforms, off great-circle-arc propagation and overtone interference. We overcome these limitations by performing systematic SNR tests, polarization analysis and minimization of overtone interference, to compute fundamental-mode LQ group-velocity dispersion and tomography across India, Himalaya and Tibet, for period range of 10–120 s. Fundamental-mode group-velocity dispersion, in this period range, is sensitive to the crust and upper-mantle structure. Lateral resolution of the group-velocity maps vary from 4$\rm ^{\circ }$ (10–40 s) to 9$\rm ^{\circ }$(90–120 s). Group-velocities (absolute and anomaly) and its lateral variations match the regional-scale geologic and tectonic features. Up to 20 s period low-velocity sedimentary layers are observed in the Bengal and Indus delta-fan complexes, Himalaya and Suleiman Mountain foreland basins, Qaidam, Tarim and Eastern Tadjik Basins. The Indian Cratons have higher group-velocities compared to the thickened Tibetan Plateau crust across the entire range of periods. At lower periods the western Tibetan Plateau is underlain by high-velocity anomaly and the central-eastern Plateau has a broad zone of low-velocity anomaly. To test the null-hypothesis of isotropy, we use isotropic $\rm S_V$ models to predict the observed LQ dispersion data. Our test negates the null hypothesis and suggest radially-anisotropic structure. Finally, we invert the LQ dispersion data to obtain horizontally-polarized shear-wave ($\rm S_H$) velocity structure beneath India–Tibet. $\rm S_H$ velocity models have an uncertainty of ∼5%. These models reveal high average $\rm S_H$ velocity (3.7–3.9 $\rm km \,\, s^{-1}$) in the Indian Cratonic crust, which extends beyond its geological outcrops, beneath the Deccan and Marwar Plateau, Southern Indian Granulite Terrane, and the Himalayan foreland basin (HFB). This is underlain by a high $\rm S_H$ velocity mantle-lid with variable thickness beneath cratons. The thickest mantle lids are beneath the Dharwar (∼150 km) and Bastar (∼180 km) Cratons. The high velocity Indian Cratonic crust and upper-mantle underthrust the Tibetan Plateau entirely in the west, up-to the Altyn-Tagh Fault (ATF); and half-way in the centre-east, up-to the Bangong-Nujiang Suture (BNS). This has lead to crustal-doubling beneath Tibet and a large-scale mid-crustal low velocity layer, bound by active faults along its edges. We use the $\rm S_H$ velocity of ≤3.0 $\rm km \,\, s^{-1}$ to delineate the regional-scale sedimentary basins. These include the Bengal and Indus delta-fan complexes with sedimentary layer thickness >15 km; the intra-cratonic HFB, Eastern Tadjik and Qaidam Basins with up-to 10 km sedimentary layer thickness. The Tarim basin has strong E-W variation in sedimentary thickness with the deepest depocentre beneath the eastern basin (>15 km), shallowing significantly west of the Mazhar-Tagh Fault to <10 km. The HFB is also marked by lateral variations in sedimentary thickness, with the thickest layers beneath the Eastern and Western Gangetic Basins (∼6–8 km) and the thinnest beneath the Indus Basin and Brahmaputra Valley (<2 km). These sub-basins are segmented by basement ridges, and the sedimentary thickness variation is controlled by flexural bending of the underthrusting Indian plate beneath the Himalaya.
SummaryMarine observation data are plentiful for constructing seafloor topography, and the integration of multi-sources data to construct a more accurate topography model remains a significant subject that continues to be explored and studied. In this study, we use geoid height (GH), Gravity (VG) and Vertical Gravity Gradient (VGG) derived from a single rectangular prism to establish the foundational observation equations for predicting topography. The effectiveness of the foundational observation equations is verified through study cases without the use of the ship measurement depth data. Additionally, the single- and multi-beam soundings data are employed as control points to integrate into the foundational observation equations for predicting topography. The prediction results demonstrate that the prediction accuracy of combined VG anomalies with ship soundings is better than GH and VGG anomalies, which is primarily because VG anomalies are effective than GH amplify high frequency signals of topography and stronger than VGG anomalies in suppressing high frequency errors. Additionally, considering the limited accuracy of marine gravity in sea region with islands and reefs, this study incorporates satellite imagery data to identify the location and size of the islands. Then, the topography of the islands is introduced and the control equations is established to jointly predict topography. The prediction results reveal the RMS errors between prediction results and single- and multi-beam sounding data are 67.4 m, which is 37.4%, 57.8% and 62.8% higher than that of SRTM 15+, DTU and ETOPO-1 models respectively. Notably, compared with the STRM 15+ model, the algorithm improves the topography accuracy of the sea area near the islands by nearly 60.8%.
