地球科学最新文献

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Reappraising the timing and spatial pattern of the Little Ice Age in China: full-field insights from the Last Millennium Climate Reanalysis Project version 2.1 中国小冰期时间和空间格局的再评价:来自上千年气候再分析项目2.1版的全方位洞见
IF 1.9 3区 地球科学
Quaternary International Pub Date : 2025-07-26 DOI: 10.1016/j.quaint.2025.109935
Miao Fang , Huan Chang
{"title":"Reappraising the timing and spatial pattern of the Little Ice Age in China: full-field insights from the Last Millennium Climate Reanalysis Project version 2.1","authors":"Miao Fang ,&nbsp;Huan Chang","doi":"10.1016/j.quaint.2025.109935","DOIUrl":"10.1016/j.quaint.2025.109935","url":null,"abstract":"<div><div>Site-specific and regionally-composited temperature reconstructions confirmed the presence of the Little Ice Age (LIA) in certain areas of China over the last millennium. However, a country-wide view of the LIA in China is still lacking, leading to ongoing debates about whether the LIA was a coherent, nationwide cold period. This study addresses this gap by analyzing the timing and spatial pattern of the LIA across China using the Last Millennium Climate Reanalysis. Key findings include: China experienced broadly cold conditions during the last millennium, but the LIA onset was notably asynchronous, in contrast to the near-synchronous termination of the LIA across China. Peak cooling occurred at different times in various regions, e.g., the 13th century in most of southern China, the 18th century in the eastern and western parts of the Qinghai-Tibet Plateau, and the 19th century in other areas. Generally, the magnitude of peak cooling increased with latitude. EOF analysis suggests the first mode accounts for 68.53 % of the total variance in temperature variability during 1200-1900 AD and indicates spatial consistency in temperature variability during this period. Weakening solar irradiance since the late 12th century is identified as the primary driver of these variations. The second mode explains 15.05 % of the total variance and reveals a north-south dipole pattern. Teleconnection factors such as the North Atlantic Oscillation and the Atlantic Multidecadal Oscillation significantly influence this mode. However, various monsoon systems across northern and southern China may play more important roles in this mode. The third mode accounts for 5.56 % of the total variance and displays tri-pole pattern (north-center-south), largely influenced by variations in the Pacific Decadal Oscillation, volcanic eruptions, and greenhouse gases. These findings provide full-field insights into the spatiotemporal characteristics of the LIA in China and enhance our understanding of this historical climate event.</div></div>","PeriodicalId":49644,"journal":{"name":"Quaternary International","volume":"745 ","pages":"Article 109935"},"PeriodicalIF":1.9,"publicationDate":"2025-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144704516","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
High-Resolution Seismic Imaging of the Seismic Gap on the Mid-to-South Segment of the Red River Fault, China 红河断裂带中南段地震间隙的高分辨率地震成像
IF 3.9 2区 地球科学
Journal of Geophysical Research: Solid Earth Pub Date : 2025-07-26 DOI: 10.1029/2025JB031601
Quan Sun, Zhen Guo, Yongshun John Chen, Shunping Pei, Yuanyuan V. Fu, Bin Luo, Xingong Tang
{"title":"High-Resolution Seismic Imaging of the Seismic Gap on the Mid-to-South Segment of the Red River Fault, China","authors":"Quan Sun,&nbsp;Zhen Guo,&nbsp;Yongshun John Chen,&nbsp;Shunping Pei,&nbsp;Yuanyuan V. Fu,&nbsp;Bin Luo,&nbsp;Xingong Tang","doi":"10.1029/2025JB031601","DOIUrl":"https://doi.org/10.1029/2025JB031601","url":null,"abstract":"<p>The Red River Fault on the southeast Tibet is a highly active fault with intense seismicity. However, a seismic gap was observed in the middle section with a seismically active zone to the southeast. We conducted seismic imaging of these two segments using dense seismic arrays, and found pronounced structural differences with high Vp, Vs, and Vp/Vs structures beneath the seismic gap and widespread low Vp, Vs, and high Vp/Vs anomalies under the active zone. The mafic rocks belonging to the Emeishan Large Igneous Province (ELIP) with high velocity and Vp/Vs ratios in the seismic gap are likely to serve as large asperities that are responsible for the long earthquake recurrence interval. In contrast, fluids and/or melts invading the seismogenic layers may expedite the evolution process and thus trigger frequent seismic events beneath the active zone. We speculate future strong earthquakes are prone to occur in the seismic gap which is presently locked, attracting sufficient attention for seismic hazard mitigation.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 7","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144705224","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Summertime Sediment Storage on the Alaskan Beaufort Shelf and Implications for Ice-Sediment Rafting and Shelf Erosion 阿拉斯加波弗特陆架夏季泥沙储藏量及其对冰沙漂流和陆架侵蚀的影响
IF 3.3 2区 地球科学
Journal of Geophysical Research-Oceans Pub Date : 2025-07-26 DOI: 10.1029/2025JC022624
E. F. Eidam
{"title":"Summertime Sediment Storage on the Alaskan Beaufort Shelf and Implications for Ice-Sediment Rafting and Shelf Erosion","authors":"E. F. Eidam","doi":"10.1029/2025JC022624","DOIUrl":"https://doi.org/10.1029/2025JC022624","url":null,"abstract":"<p>Arctic coastlines are known to be rapidly eroding, but the fate of this material in the coastal ocean (and the sedimentary dynamics of Arctic continental shelves in general) is less well-constrained. This study used summertime mooring data from the Alaskan Beaufort Shelf to study sediment-transport patterns which are dominated by waves and wind-driven currents. Easterly wind events account for most of the seasonal sediment transport, and serve to focus sediment on the inner shelf. This is a key finding because it means that sediment is readily available for wave-driven resuspension and sea-ice entrainment during fall storms. Sediment-ice entrainment has been previously implicated as a major mechanism for Arctic Shelf erosion—and so the summertime focusing of sediment observed in this study may actually serve to enhance shelf erosion rather than promote shelf sediment accumulation. In a pan-Arctic context, the Alaskan Beaufort Shelf is somewhat similar to the Laptev Sea Shelf, where previous work has shown that sediment is also focused during the summer months (but for different reasons related to estuarine-like circulation under the Laptev plume). The Alaskan Beaufort Shelf example contrasts with previous work on the Canadian Beaufort Shelf, where dominant winds from the opposite direction (northwest) likely promote strong seaward dispersal of sediment rather than inner-shelf convergence. This study thus highlights the importance of understanding dominant wind patterns when considering seasonal and inter-annual storage, transport, and erosion of sediments from Arctic continental shelves.</p>","PeriodicalId":54340,"journal":{"name":"Journal of Geophysical Research-Oceans","volume":"130 7","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144705440","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Parametric Sensitivity of Hemispheric Albedo Symmetry Weakly Constrains Shortwave Cloud Radiative Feedbacks in the Community Atmosphere Model Version 6 社区大气模式第6版中半球反照率对称的参数敏感性弱约束短波云辐射反馈
IF 4.6 1区 地球科学
Geophysical Research Letters Pub Date : 2025-07-26 DOI: 10.1029/2025GL115948
Aiden Jönsson, Maria Rugenstein, Frida A.-M. Bender, Daniel McCoy, Trude Eidhammer
{"title":"Parametric Sensitivity of Hemispheric Albedo Symmetry Weakly Constrains Shortwave Cloud Radiative Feedbacks in the Community Atmosphere Model Version 6","authors":"Aiden Jönsson,&nbsp;Maria Rugenstein,&nbsp;Frida A.-M. Bender,&nbsp;Daniel McCoy,&nbsp;Trude Eidhammer","doi":"10.1029/2025GL115948","DOIUrl":"https://doi.org/10.1029/2025GL115948","url":null,"abstract":"<p>Earth's albedo is symmetric between the northern and southern hemispheres (NH and SH, respectively) because SH clouds compensate for higher NH clear-sky albedo, a feature that climate models have difficulty capturing. We assess how parameterized processes affect a model's cloud albedo and albedo symmetry using a perturbed parameter ensemble (PPE) of atmospheric simulations. Parameters most significant to simulated albedo symmetry impact precipitation, turbulent dissipation, and sea salt aerosol emissions. Constraining the PPE's shortwave cloud feedbacks using the observed albedo symmetry yields a range of +0.61 <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>±</mo>\u0000 </mrow>\u0000 <annotation> $pm $</annotation>\u0000 </semantics></math> 0.24 W m<sup>−2</sup> K<sup>−1</sup> (66% confidence), which is stronger than that of the model's control simulation due to parameter settings that lead to greater loss of subtropical low clouds and weaker negative cloud phase feedback. Although these settings would reduce cloud albedo bias compared to the control simulation, we find that albedo symmetry has limited potential as a constraint for cloud feedbacks on its own.</p>","PeriodicalId":12523,"journal":{"name":"Geophysical Research Letters","volume":"52 14","pages":""},"PeriodicalIF":4.6,"publicationDate":"2025-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025GL115948","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144705695","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Asymmetries in the Temporal Variation of the Electron Content During a Solar Eclipse 日蚀期间电子含量时间变化的不对称性
IF 2.9 3区 地球科学
Earth and Space Science Pub Date : 2025-07-26 DOI: 10.1029/2025EA004372
A. Meza, G. Bosch, M. P. Natali, B. Eylenstein, A. Urutti
{"title":"Asymmetries in the Temporal Variation of the Electron Content During a Solar Eclipse","authors":"A. Meza,&nbsp;G. Bosch,&nbsp;M. P. Natali,&nbsp;B. Eylenstein,&nbsp;A. Urutti","doi":"10.1029/2025EA004372","DOIUrl":"https://doi.org/10.1029/2025EA004372","url":null,"abstract":"<p>Solar eclipses offer a unique opportunity to study rapid variations in the Earth's atmosphere. By accurately modeling the timing and magnitude of obscuration caused by the Moon's shadow, we can investigate the eclipse's impact on the behavior of the Earth's ionosphere. Our approach involves deriving the vertical total electron content (VTEC) of the ionosphere using navigation satellite signals. Our previous research, conducted during the 2017 North American eclipse, focused on a limited area. We employed a skewed Gaussian profile to model the temporal variation of the <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>Δ</mi>\u0000 </mrow>\u0000 <annotation> ${Delta }$</annotation>\u0000 </semantics></math>VTEC curve, introducing a new parameter to better characterize the time delay in the ionosphere's response. This study broadens our research to include the East Coast and integrates the Global Ionosphere-Thermosphere Model (GITM). The skewness parameter reflects the relative durations of ionospheric decay and recovery, where positive values indicate rapid decay coupled with slow recovery and negative values suggest the opposite. Although our <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mi>Δ</mi>\u0000 </mrow>\u0000 <annotation> ${Delta }$</annotation>\u0000 </semantics></math>VTEC simulation using GITM qualitatively matches observed behaviors, it faces challenges in accurately capturing the maximum drop and recovery phases, particularly in the eastern regions, likely due to insufficient consideration of plasmaspheric refilling, which significantly influences the recovery of the upper ionospheric layers. The path of the eclipse totality delineates a boundary where positive asymmetries are observed to the south while negative asymmetries appear to the north.</p>","PeriodicalId":54286,"journal":{"name":"Earth and Space Science","volume":"12 7","pages":""},"PeriodicalIF":2.9,"publicationDate":"2025-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025EA004372","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144705163","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Modern-like seawater δ18O in the mesoproterozoic: Insights from triple oxygen isotopes of chert 中元古代现代海水δ18O:来自燧石三氧同位素的启示
IF 4.8 1区 地球科学
Earth and Planetary Science Letters Pub Date : 2025-07-26 DOI: 10.1016/j.epsl.2025.119548
Bokai Dai , Chenqing Li , Haoran Ma , Bing Shen , Yongbo Peng , Xiaobin Cao
{"title":"Modern-like seawater δ18O in the mesoproterozoic: Insights from triple oxygen isotopes of chert","authors":"Bokai Dai ,&nbsp;Chenqing Li ,&nbsp;Haoran Ma ,&nbsp;Bing Shen ,&nbsp;Yongbo Peng ,&nbsp;Xiaobin Cao","doi":"10.1016/j.epsl.2025.119548","DOIUrl":"10.1016/j.epsl.2025.119548","url":null,"abstract":"<div><div>Oxygen isotope compositions in ancient seawater (δ<sup>18</sup>O<sub>SW</sub> and Δ<sup>’17</sup>O<sub>SW</sub>) are key proxies for deciphering past climate and tectonic regimes. Despite various reconstruction attempts, a consensus on their history remains elusive. Chert, valued for its diagenetic stability, offers a promising archive, particularly through triple oxygen isotope analysis. However, Precambrian cherts frequently exhibit deviations in δ<sup>18</sup>O and Δ<sup>’17</sup>O from triple oxygen isotope equilibrium, complicating interpretations. Here, we propose that this deviation results from the coprecipitation of oxygen-bearing minerals (detrital silicates, authigenic clays, and barite), each with distinct isotopic signatures. To test this hypothesis, we analyzed Mesoproterozoic chert samples from the Yangzhuang and Wumishan formations in North China. Our results show a significant correlation between chert δ<sup>18</sup>O and detrital silicate content, with coexisting oxygen-bearing minerals driving deviations in δ<sup>18</sup>O and Δ<sup>’17</sup>O from equilibrium. The δ<sup>18</sup>O and Δ<sup>’17</sup>O values of the purest, most pristine chert samples suggest that Mesoproterozoic seawater had a δ<sup>18</sup>O similar to that of modern seawater (i.e. ∼ -1 ‰, ice free world seawater), a conclusion further supported by our oxygen balance model. This study demonstrates that using pure chert or an oxygen balance model is essential for accurately reconstructing ancient δ<sup>18</sup>O<sub>SW</sub>.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"668 ","pages":"Article 119548"},"PeriodicalIF":4.8,"publicationDate":"2025-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144704320","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Recruitment and Dispersal of Post-Wildfire Debris Flows 野火后泥石流的增加和扩散
IF 3.5 2区 地球科学
Journal of Geophysical Research: Earth Surface Pub Date : 2025-07-26 DOI: 10.1029/2025JF008325
Thomas Dunne, Paul Alessio, Kristin D. Morell
{"title":"Recruitment and Dispersal of Post-Wildfire Debris Flows","authors":"Thomas Dunne,&nbsp;Paul Alessio,&nbsp;Kristin D. Morell","doi":"10.1029/2025JF008325","DOIUrl":"https://doi.org/10.1029/2025JF008325","url":null,"abstract":"<p>Quantifying sequences of events and materials involved in the growth and dispersal of post-wildfire debris flows across entire mountain catchments and piedmont fans is rarely possible. However, understanding these processes facilitates assessing future flow magnitudes and recurrence risk. This study analyzed the evolution of debris flows generated by a rainstorm following near-complete burning of vegetation in six mountain watersheds. The flows transported large volumes of boulders to downstream fans, devastating Montecito, California. With rainfall-runoff modeling, lidar, photogrammetry, and field surveys, we quantified the hydrological and sedimentological components of the debris flows as they evolved from hillslope runoff to boulder-rich fan deposits and ocean discharge. Runoff from burned soils drove larger amounts of rill erosion and slurry generation on shale hillslopes than on sandstones. Hillslope slurry mobilized ravel deposits and fine sediments stored in the channel network, mainly on shales. Channels draining sandstones mainly supplied the flows' boulder loads. One-quarter of the mountain-shed sediment escaped to the ocean, while all boulders settled on the fans. Flows confined to primary channels remained erosive across the fans except where channel gradients and dimensions decreased in response to fault-related topography and where bridges trapped boulders, intensifying in-channel and overbank deposition. Although the results derive from a single event, they illustrate how a sequence of processes and landscape conditions determine debris-flow evolution across catchments and fans. Identifying debris-flow components highlights useful measurement and modeling methods to improve prediction while highlighting current limits on understanding critical processes and transient antecedent conditions.</p>","PeriodicalId":15887,"journal":{"name":"Journal of Geophysical Research: Earth Surface","volume":"130 7","pages":""},"PeriodicalIF":3.5,"publicationDate":"2025-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1029/2025JF008325","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144705164","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
On the Subduction Polarity Beneath the Semail Ophiolite 论Semail蛇绿岩的俯冲极性
IF 3.9 2区 地球科学
Journal of Geophysical Research: Solid Earth Pub Date : 2025-07-26 DOI: 10.1029/2025JB032145
Simone Pilia
{"title":"On the Subduction Polarity Beneath the Semail Ophiolite","authors":"Simone Pilia","doi":"10.1029/2025JB032145","DOIUrl":"https://doi.org/10.1029/2025JB032145","url":null,"abstract":"<p>The Semail ophiolite and the UAE-Oman mountain range offer a rare window into continental subduction and exhumation. Despite almost half a century of conflicting studies, the geometry and number of subductions that characterized the formation of the ophiolite and subsequent obduction remain debated. Competing tectonic models range from a single NE-directed subduction that initiated with ophiolite and sole formation at <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 </mrow>\u0000 <annotation> ${sim} $</annotation>\u0000 </semantics></math>96–95 Ma, to scenarios involving multiple metamorphic events linked to opposite subduction polarities - including prograde metamorphism at <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 </mrow>\u0000 <annotation> ${sim} $</annotation>\u0000 </semantics></math>110–130 Ma followed by retrograde metamorphism at <span></span><math>\u0000 <semantics>\u0000 <mrow>\u0000 <mo>∼</mo>\u0000 </mrow>\u0000 <annotation> ${sim} $</annotation>\u0000 </semantics></math>80 Ma–or models proposing the juxtaposition of two separate subduction zones. This study investigates the tectonic evolution of the Semail ophiolite, and the subduction polarity structurally beneath it using 3-D P- and S-wave tomographic models integrated with global tomographic datasets, plate reconstruction frameworks, and surface geology. The results reveal a northeast-dipping high-velocity anomaly extending 250 km beneath the metamorphic sole exposed in the northern mountain range, and 150 km beneath Jebel Akhdar, which I interpret as remnants of the Neo-Tethyan slab attached to the Arabian continental margin. These observations offer a plausible explanation for the contrasting exhumation conditions between the northern and southern segments of the mountain range. In the southern region, evidence of possible slab detachment is consistent with the exhumation of high-pressure rocks, such as those exposed in the Saih Hatat Dome. This study challenges earlier hypotheses of southwest-directed subduction and strongly supports a single northeast-dipping subduction system, providing new insights into continental subduction, obduction, exhumation, and the creation of orogenic belts.</p>","PeriodicalId":15864,"journal":{"name":"Journal of Geophysical Research: Solid Earth","volume":"130 7","pages":""},"PeriodicalIF":3.9,"publicationDate":"2025-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144705226","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Experimental constraints on the shock history of CI chondrites and Ryugu grains CI球粒陨石和Ryugu颗粒冲击历史的实验约束
IF 4.8 1区 地球科学
Earth and Planetary Science Letters Pub Date : 2025-07-26 DOI: 10.1016/j.epsl.2025.119559
Toru Nakahashi , Masaaki Miyahara , Akira Yamaguchi , Takamichi Kobayashi , Hitoshi Yusa , Masashi Miyakawa , Naotaka Tomioka , Yuto Takaki , Takaaki Noguchi , Toru Matsumoto , Akira Miyake , Yohei Igami , Yusuke Seto
{"title":"Experimental constraints on the shock history of CI chondrites and Ryugu grains","authors":"Toru Nakahashi ,&nbsp;Masaaki Miyahara ,&nbsp;Akira Yamaguchi ,&nbsp;Takamichi Kobayashi ,&nbsp;Hitoshi Yusa ,&nbsp;Masashi Miyakawa ,&nbsp;Naotaka Tomioka ,&nbsp;Yuto Takaki ,&nbsp;Takaaki Noguchi ,&nbsp;Toru Matsumoto ,&nbsp;Akira Miyake ,&nbsp;Yohei Igami ,&nbsp;Yusuke Seto","doi":"10.1016/j.epsl.2025.119559","DOIUrl":"10.1016/j.epsl.2025.119559","url":null,"abstract":"<div><div>C-type asteroids, which make up a significant portion of the main belt asteroids, are believed to be composed of materials similar to CI and CM carbonaceous chondrites. In this study, we conducted shock recovery experiments on the Orgueil CI and CI affinity Yamato 980115 CY (partly dehydrated CI) chondrites to examine their mineralogical and textural changes under impact conditions. Our results indicate that weak shock pressures below approximately 4 GPa do not produce significant shock metamorphic features, supporting the current interpretation that most Ryugu grains experienced shock pressures within this range. Above approximately 4 GPa, dehydration and degassing of Mg-Fe phyllosilicates and carbonaceous materials become dominant, leading to rock fragmentation along cracks. Rock melting initiates above approximately 10 GPa, leading to the formation of frothy regions composed of iron-rich amorphous material containing numerous small, rounded voids. These voids are generated by the degassing of volatiles (H₂O and CO₂) during shock-induced melting or vitrification. These findings suggest that the regolith layer of asteroid Ryugu was primarily formed by the reassembly of rock fragments exfoliated by impacts without undergoing strong shock metamorphism. However, highly shocked materials may be buried beneath the regolith layer, highlighting the need for further investigations into the interiors of C-type asteroids to better understand their thermal and impact histories.</div></div>","PeriodicalId":11481,"journal":{"name":"Earth and Planetary Science Letters","volume":"668 ","pages":"Article 119559"},"PeriodicalIF":4.8,"publicationDate":"2025-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144704319","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
Mapping priority zones for urban heat mitigation in Shanghai: Heat risk vs. shelter provision 绘制上海城市热缓解优先区域:热风险与住房供应
IF 7.1 1区 地球科学
Computers Environment and Urban Systems Pub Date : 2025-07-26 DOI: 10.1016/j.compenvurbsys.2025.102330
Wenqi Qian , Fujie Rao , Xiaoyu Li , Dayi Lai
{"title":"Mapping priority zones for urban heat mitigation in Shanghai: Heat risk vs. shelter provision","authors":"Wenqi Qian ,&nbsp;Fujie Rao ,&nbsp;Xiaoyu Li ,&nbsp;Dayi Lai","doi":"10.1016/j.compenvurbsys.2025.102330","DOIUrl":"10.1016/j.compenvurbsys.2025.102330","url":null,"abstract":"<div><div>Global climate change has intensified heat wave events, raising their intensity, duration, and frequency. Outdoor urban green spaces and indoor air-conditioned spaces serve as critical ‘heat shelters’, providing crucial cooling relief to extreme heat. However, there is a lack of studies focused on the spatial distribution of potential heat shelters and how shelters in different urban areas match varying degrees of heat risk. To address this research gap, we quantify and map heat risks and shelter provisions of administrative neighborhoods (often the smallest level of urban governance) and walkable grids of 500 × 500 m (a commonly-used comfortable walking distance for vulnerable groups such as the elderly people), and identify vulnerable areas where heat mitigation interventions should be prioritized. We select Shanghai – a metropolis of around 25 million people experiencing increasingly extreme heat wave events - for the case study. We measure heat risk by a composite index incorporating heat hazard, exposure and vulnerability. We largely measure heat provision by the number of indoor air-conditioned venues and outdoor green spaces, weighted by their time availability. Our findings reveal a general decrease in heat mitigation priority levels from the urban core to the suburbs, a pattern that is consistent between neighborhoods and grids at the metropolitan scale. This said, at smaller scales, significant differences between these two types of spatial units emerged in the degree and distribution of heat mitigation priority levels, revealing nuanced, inequitable capacities of different urban areas to tackle extreme heat. Our study provides a novel and systematic lens for assessing heat mitigation priority levels, informing more effective strategies for planning and managing heat shelters and allocating heat mitigation resources.</div></div>","PeriodicalId":48241,"journal":{"name":"Computers Environment and Urban Systems","volume":"121 ","pages":"Article 102330"},"PeriodicalIF":7.1,"publicationDate":"2025-07-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144704836","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
引用次数: 0
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