Earth-Science Reviews最新文献

Sedimentary and volcanic tablelands host the world's largest landslide areas, sometimes spanning hundreds of kilometers along escarpments. This study, employing new remote sensing-based mapping and drawing on an expanding body of literature on paleogeographic evolution, revises the extent, controls, and chronology of some of Earth's largest coalescent landslides in the volcanic tableland of extra-Andean Patagonia. Mostly ancient rotational slides and rock spreads, accompanied by earthflows and occasional rock avalanches, cover approximately 30,000 km², roughly a fifth of the Patagonian escarpments, with the largest landslide areas exceeding 1000 km². The immense size of the failed tableland in Patagonia is inherited from stratigraphy and geological history: weak marine and continental Cretaceous-Miocene sedimentary and volcaniclastic rocks, capped by plateau basalts, create a highly unstable environment, outcropping along thousands of kilometers of escarpments. Most landslide areas occupy the steepest, most dissected parts of Patagonian tableland, occurring independently of recent climatic conditions. Some of the largest complexes are found in both the most humid and arid regions. Cross-cutting relationships between landslides and dated glacial, lacustrine, marine deposits, and lava flows reveal that some landslides have persisted for several million years, marking them as some of Earth's oldest landslide terrains with distinctive geomorphological footprints. Future research on failed Patagonian tableland should include direct radiometric dating, InSAR technology monitoring, and numerical stability modeling of landslides. This comprehensive approach will deepen our understanding of their origins and determine whether these giant landslide fringes predominantly represent fossil features or could be reactivated under contemporary environmental conditions.

Earthquake-induced liquefaction is a prominent and impactful natural hazard responsible for substantial economic losses worldwide. Hence, engineers and researchers are currently interested in developing methods and techniques to mitigate this destructive phenomenon. Reducing the degree of saturation is a reliable method to improve the liquefaction resistance of sandy soils since it directly influences the pore pressure build-up during seismic action. This paper reviews the mechanisms and assessment of earthquake-induced liquefaction in sandy soils with various degrees of saturation, a crucial parameter for reducing the phenomenon triggering. In addition, it presents novel approaches that delve into interpreting cyclic behaviour with diverse degrees of saturation using stress-based and energy-based approaches. The experimental results compiled and discussed show that, effectively, reducing the degree of saturation holds promise as a viable strategy for enhancing soil liquefaction resistance and mitigating associated risks. Moreover, the interpretation of cyclic behaviour addressed in this paper offers valuable insights into the reliability of interpreting methods to quantify the liquefaction resistance under several degrees of saturation (that may be achieved by desaturation or induced partial saturation techniques), contributing to strategies for resilience against earthquake-induced damages.

Fracture-filling hydrate constitutes a pivotal component within the global hydrate reserves and serve as a significant focal point for hydrate exploration and development. However, the understanding of the formation mechanisms and geophysical properties of fracture-filling hydrate in sediments remains unclear. This review seeks to bridge this knowledge gap by comprehensively examining the formation mechanisms of fracture-filling hydrate from both micro-sedimentary and geological reservoir perspectives. It delves into various aspects of field tests, including seismic and logging, as well as laboratory tests covering acoustic properties, permeability, thermal properties, electrical resistivity, and mechanical properties. It aims to shed light on the challenges associated with the characteristics of fracture-filling hydrate reservoirs and their geophysical properties while proposing potential solutions, and emphasizes the urgency of identifying the formation patterns of fracture-filling hydrate and estimating resource volumes. Furthermore, the review emphasizes the importance of collaborative geophysical characterization testing for fracture-filling hydrate as a crucial step in addressing this challenge. It advocates for fostering international cooperation for global data integration and sharing as a viable solution to advance our understanding and management of these valuable resources.

South America figures as one of the most fruitful continents for paleontological research on the Ediacaran-Cambrian transition, with almost 100 years of studies on organisms preserved in carbonates and siliciclastic successions deposited during the birth of the Gondwana supercontinent. However, this scientific record is often scattered among local publications which is part of the reason for the unfamiliarity of geoscientists with the Ediacaran paleontology of this continent. To address this issue, this paper provides a comprehensive overview of Ediacaran paleontology in South America. It achieves this by conducting a thorough assessment of existing research alongside presenting ample new data concerning fossil discoveries. Following current efforts to add new pieces to the complex puzzle on metazoan evolution, this contribution resumes our understanding of the variety and diversity of Ediacaran assemblages in this part of the planet. Positioning South American successions in space and time and comparing them with occurrences worldwide helps us understand the different pulses of extinctions, and their forcings and consequences for life diversification during the Ediacaran. Lastly, by definitively adding the paleontological record of SW Gondwana to the global picture, we seek to contribute to current discussions on the subdivision of the Ediacaran, perhaps the most emblematic period in the geological record.

Submarine debris flows occur under the cloak of the sea and are giants among other types of landslides on planet Earth. They pose a significant threat to sustainable offshore development and marine ecosystems. Existing research on these flows mainly rely on back-analyzing field events and conducting miniaturized experiments. However, it is unclear whether the dynamics of miniaturized flows are similar to field ones. In this review, dimensional analysis is used to evaluate laboratory and field data collated from the literature to compare the dynamics of submarine debris flows at different scales. Miniaturized flows are demonstrated to have disproportionately low yield stress and viscosity compared to field flows. The low yield stress is caused by the need to reduce the clay content of a model debris mixture so that it can flow under substantially reduced gravitational driving stresses in laboratory conditions. Consequently, some proposed scaling relationships in the literature derived from laboratory experiments need to be used with caution. Specifically, both the Reynolds and Bingham numbers cannot independently provide a scale-invariant criterion for distinguishing between laminar and turbulent flows. Instead, the Hampton number, with a threshold >0.001, is proposed for the design of the yield stress and clay contents of laboratory flows. Moreover, reduced model viscous stress drastically reduces erosion potential, which limits the existing understanding of the excess fluid pressures generated at the flow-bed interface, and thus flow mobility. The mobility of field flows is generally attributed to hydroplaning. However, this conjecture mainly stems from experiments with impervious boundaries. Such an idealization exaggerates the effects of excess fluid pressures that develop during hydroplaning. An enhanced understanding of the differences in dynamics between field and modeled flows can improve the design of future experiments to model submarine debris flows.