Article
Geosciences, Multidisciplinary
Yage Zhu, Faqi Diao, Rongjiang Wang, Ming Hao, Zhigang Shao, Xiong Xiong
Summary: Knowledge of lithospheric rheology provides fundamental insights into crustal deformation near the Longmen Shan fault (LMSF). The study reveals a high-viscosity zone beneath the LMSF, where the steady-state viscosity is significantly higher than the transient viscosity. Furthermore, the effective lower crustal viscosity decreases immediately after the earthquake and recovers to interseismic level.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Geochemistry & Geophysics
Dawei Jiang, Shimin Zhang, Rui Ding
Summary: This study focused on the deformation pattern and shortening rate of the complex foreland area in the southern Longmen Shan, using net-based RTK measurement and Quaternary chronology to determine a total shortening rate of 2.06 mm/yr for the foreland in southern Longmen Shan. This suggests that crustal shortening is the dominating force in the current orogenesis of the Longmen Shan, supporting a mechanical model that shows the tectonic pattern in the region.
Article
Chemistry, Analytical
Feng Liu, Xin Yao, Lingjing Li
Summary: Geomorphic indices were used to detect significant variations in stream power along river reaches in the Zengqu River watershed, potentially associated with landslides. Most landslide anomalies were found along the trunk and surrounding tributaries, indicating an upstream migration of erosional wave. The proposed methodology can improve the detection of potential landslide zones and the identification of drainage network areas at risk of landslides.
Article
Geochemistry & Geophysics
Ruizhi Jin, Xiaohui He, Hongjian Fang, Jun Xie, Ying Liu, Peizhen Zhang
Summary: The study quantifies the effect of topography on ambient noise tomography (ANT) using numerical simulations. The results show that the topography has a negligible effect on ANT in relatively flat regions, but significantly biases the shear wave velocity image in areas with large topographic variation.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Environmental Sciences
Tanguang Gao, Yulan Zhang, Shichang Kang, Benjamin W. Abbott, Xiaoming Wang, Tingjun Zhang, Shuhua Yi, Orjan Gustafsson
Summary: The rate of permafrost collapse is accelerating on the Tibetan Plateau, with the area of collapsed permafrost increasing by approximately a factor of 40 from 1969 to 2017, with 70% of the collapsed area forming since 2004. These widespread perturbations could trigger changes in local ecosystem state and amplify large-scale permafrost climate feedbacks.
ENVIRONMENTAL RESEARCH LETTERS
(2021)
Article
Geography, Physical
Qi Su, Xianyan Wang, Huayu Lu, Huiping Zhang, Hong Xie
Summary: This study introduces an example of river piracy and its geomorphological implications in the Northern Qilian Shan region. The results confirm the occurrence of river piracy in the area and suggest that drainage reorganization is a common landform process during the outward growth of the Qilian Shan.
PALAEOGEOGRAPHY PALAEOCLIMATOLOGY PALAEOECOLOGY
(2022)
Article
Geosciences, Multidisciplinary
Chaopeng Li, Dewen Zheng, Renjie Zhou, Jingxing Yu, Yizhou Wang, Jianzhang Pang, Ying Wang, Yuqi Hao, Youjuan Li
Summary: The study examines the exhumation history of the East Kunlun Shan in the northeastern Tibetan Plateau using low-temperature thermochronology, revealing earlier thrust faulting in the EKLS compared to tectonic uplift in the South Qilian Shan and North Qilian Shan. This suggests the northeastern margin of the Tibetan Plateau has migrated from the EKLS to the North Qilian Shan since the late Oligocene.
GEOPHYSICAL RESEARCH LETTERS
(2021)
Article
Engineering, Environmental
Liyong Wang, Zongji Yang, Gang Liu, Shihao Liu, Xiaolong Fu, Jianping Qiao
Summary: Using unmanned aerial vehicles, this study conducted a comprehensive field investigation to observe the special landforms of the Dora Kamiyama rockslide in the Tibetan Plateau, analyzing the dynamic processes of the rockslide based on the complex topography. The results revealed different geological processes and landform features in different areas of the rockslide. Finally, dynamic parameters of the rockslide were calculated, determining the occurrence time of the rockslide to be an ancient landslide in the Holocene.
BULLETIN OF ENGINEERING GEOLOGY AND THE ENVIRONMENT
(2021)
Article
Geosciences, Multidisciplinary
Heng Peng, Jianqiang Wang, Chiyang Liu, Ming Ma, Qian Ma, Keliang Li, Jinli Pan, Jiaoli Li, Yang Qin, Qiangwang Xie, Massimiliano Zattin
Summary: This study used apatite fission-track analysis to determine the uplift and exhumation history of the eastern Qilian Shan in the Tibetan Plateau. The results showed that the main stage of growth and thickening occurred during the Middle Jurassic-Early Cretaceous, and the Late Cretaceous was a period of intense uplift and deformation. The cooling of the eastern margin of the Qilian Shan during the Late Eocene-Early Miocene was attributed to crustal extension. The study also found no evidence of intense reactivation in the late Cenozoic period in the Xiji region. These findings have implications for regional hydrocarbon exploration.
MARINE AND PETROLEUM GEOLOGY
(2022)
Article
Geochemistry & Geophysics
Xiaofei Hu, Jiakun Wu, Zhenling Wen, Jiaxin Zhang, Qiming Zhao, Baotian Pan
Summary: In an active thrust-fold belt, the evolution of drainage patterns plays a significant role in surface erosion and sedimentary sequences. This study focuses on the Yumu Shan range and reveals the transition from a transverse river to a longitudinal river, proposing a conceptual model for the drainage evolution in active fold-thrust belts.
EARTH AND PLANETARY SCIENCE LETTERS
(2022)
Article
Environmental Sciences
Shengli Yang, Yuanlong Luo, Qiong Li, Weiming Liu, Zixuan Chen, Li Liu, Xiaojing Liu
Summary: The Tibetan Plateau is identified as a significant dust source, with research indicating that the eastern TP loess primarily originates from the TP interior, based on similar elemental characteristics to surface sediments on the plateau.
SCIENCE OF THE TOTAL ENVIRONMENT
(2021)
Article
Geochemistry & Geophysics
Zhicheng Zhou, Danping Yan, Liang Qiu, Ruoyan Kong, Huajie Song, Dongzhi Xiao, Xiaohan Lin, Chao Du, Fei Kong
Summary: Reconstructing the deformation sequence and strain history of the Longmen Shan thrust belt has significant implications for the growths of the SW Qinling orogenic belt and the Tibetan Plateau. A comprehensive structural investigation and measurements of magnetic fabrics were conducted, revealing four phases of deformation and strain evolution from incipient deformation to cleavage fabrics. The results suggest non-coaxial growth of the SW Qinling orogenic belt and the Tibetan Plateau.
Article
Geosciences, Multidisciplinary
Feng Jiang, Xiaobin Chen, Martyn J. Unsworth, Juntao Cai, Bing Han, Lifeng Wang, Zeyi Dong, Tengfa Cui, Yan Zhan, Guoze Zhao, Ji Tang
Summary: The 3D resistivity model of the Gongga Shan region obtained through inversion of magnetotelluric data reveals that the uplift of the mountain is primarily attributed to the underthrusting of the Yangtze Craton, with additional uplift possibly due to transpression on a restraining bend of the Xianshuihe faults. This model challenges previously published geodynamic models and provides new insights into the geological processes at play in the region.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Geochemistry & Geophysics
Mei Feng, Hui Qian, James Mechie, Meijian An, Haibing Li, Guangqi Xue, Heping Su, Xiang Cui
Summary: The seismic array along the Longmen Shan fault belt provided densely distributed inter-station cross-correlated surface waves for constructing a new 3-D crustal S-wave velocity model. The model highlights several crustal structure features, including high crustal velocities in certain areas and low velocities in others, as well as low-velocity belts perpendicular to the fault belt. These findings suggest different crustal characteristics and movements along the fault belt, impacting the tectonic activities in the region.
Article
Meteorology & Atmospheric Sciences
Long Yang, Jie Ma, Xianyan Wang, Fuqiang Tian
Summary: This study examines extreme rainfall and flooding over the eastern Tibetan Plateau (TP) and establishes the link between large-scale synoptic environment, mesoscale process, and regional flood hydrology. The results show that the transitional pattern form Asian summer monsoons to midlatitude systems is the most frequent synoptic condition for flooding, and the interplay between complex terrains and moisture transport determines the contrasting flood characteristics. The study also highlights the interaction of complex terrains and nocturnal low level jets as the key mesoscale ingredients in dictating a pronounced diurnal cycle of extreme rainfall.
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
(2022)
Article
Geology
Bo Hui, Yunpeng Dong, Franz Neubauer, Shuai He, Jan Varga
Summary: The Neoproterozoic Zhoutan Group in South China provides an important record of sedimentary system, with new detrital zircon U-Pb dating revealing its depositional age, provenance mainly from the Jiangnan Orogen, and metamorphic history during the Silurian period. These findings suggest its tectonic affinity between the Yangtze and Cathaysia Blocks with a potential boundary north of its current location.
INTERNATIONAL GEOLOGY REVIEW
(2021)
Article
Geology
Chen Yang, Yunpeng Dong, Hui Wang, Zhongyue Lin, Youyun Liao, Shangpeng Zhang, Huan Liu
Summary: This study discovers a newly formed seamount on the Tianshuihai terrane, which exhibits typical characteristics of oceanic island basalts (OIBs). Zircon U-Pb dating reveals a Late Ordovician crystallization age for the seamount. Detrital zircon analysis suggests that parts of the sediment likely originated from the remnant of the Proto-Tethys Ocean and were deposited on or accreted into the seamount during oceanic crust subduction. This finding provides robust evidence for the evolution of the Mazar-Kangxiwar suture zone (MKSZ) in the Proto-Tethys Ocean and supports its inclusion as part of the Western Kunlun orogenic belt (WKOB).
INTERNATIONAL GEOLOGY REVIEW
(2022)
Article
Geosciences, Multidisciplinary
Bo Hui, Yunpeng Dong, Feifei Zhang, Shengsi Sun, Shuai He
Summary: The study on the Neoproterozoic sedimentary successions of the Hengdan Group on the NW Yangtze Block used detrital zircon U-Pb dating and geochemistry to determine a maximum depositional age of c. 720 Ma and intermediate to felsic sources for sediments accumulated in a basin related to an active continental margin geodynamic setting. These findings support proposals for subduction-related tectonics along the western margin of the Yangtze Block during the early Neoproterozoic.
GEOLOGICAL MAGAZINE
(2021)
Article
Geology
Bo Hui, Yunpeng Dong, Feifei Zhang, Shengsi Sun, Shuai He
Summary: This study presents new insights into the formation of the Neoproterozoic mafic intrusions in the Bikou Terrane, indicating that they were likely derived from partial melting of a mantle wedge source metasomatized by slab-derived melts. The interaction between upwelling enriched asthenospheric mantle and mantle wedge peridotite may have been triggered by the slab rollback process in a subduction-related environment, supporting the persistent subduction-related system along the northwestern margin of the Yangtze Block during the early Neoproterozoic.
ORE GEOLOGY REVIEWS
(2021)
Article
Geosciences, Multidisciplinary
Xiao-Fei Xu, Long-Long Gou, Yun-Peng Dong, Xiao-Ming Liu, Zheng-Hui Li, Cheng-Li Zhang, Xiao-Ping Long, Yu-Hang Zhao, Feng Zhou
Summary: The quartz monzodiorites from the Helanshan Complex were formed through fractional crystallization of mantle-derived magma and assimilation of crustal material in a post-collisional setting. These rocks record a tectonic transition from compression to extension during the period around 1.95-1.93 billion years ago.
PRECAMBRIAN RESEARCH
(2021)
Article
Geography, Physical
Xiaohui Shi, Zhao Yang, Yunpeng Dong, Li Zhang
Summary: The study reveals that the erosion rates of the northern Qinling Mountains are controlled by topographic steepness, with active tectonics playing a key role in the spatial distribution of erosion. Precipitation and lithology have limited influence on erosion, while the active tectonic activity along the Qinling Piedmont Fault and the Taibai Fault is crucial in shaping erosion patterns in this region.
Article
Geology
Yuangang Yue, Yunpeng Dong, Shengsi Sun, Dengfeng He, Bo Hui, Xiang Ren, Bin Zhang, Weidong He
Summary: The Buqingshan Complex, a part of the Muztagh-Buqingshan-Anemaqen ophiolitic melange zone, contains oceanic rocks that represent remnants of the Paleo-Tethys Ocean. These rocks exhibit characteristics of abyssal peridotites, normal mid-ocean ridge basalts (N-MORB), and oceanic island basalts (OIB). The geological, geochemical, and geochronological data suggest that the Late Palaeozoic N-MORB- and OIB-type rock assemblages are most likely fragments of mid-ocean ridge oceanic lithosphere and seamounts, respectively, representing the evolution stages of the Paleo-Tethys Ocean.
INTERNATIONAL GEOLOGY REVIEW
(2022)
Article
Geology
Jing-Yi Wang, M. Santosh, Toshiaki Tsunogae, Sung Won Kim, Yun-Peng Dong
Summary: Subduction zones act as gateways for large-scale material and energy exchange. In the SW Japan region, ongoing convergent margin processes with island arc magmatism are important to understand. This study investigates bimodal magmatic suites in the Tsukuba area of Japan, revealing Hbl-gabbros and granitoids with distinct characteristics. The petrological and geochemical features of these rocks suggest a connection between Cretaceous arc magmatism in Tsukuba and the magmatic belt in SW Japan.
INTERNATIONAL GEOLOGY REVIEW
(2022)
Article
Geology
Xianfeng Zha, Yunpeng Dong, Dengfeng He, Meng Li, Xiaofeng Gao, Xiaoming Liu, Chaobin Hu, Lili Xu
Summary: The Qimantagh back arc basin underwent complex tectonic evolution processes, including opening, subduction, and closure. The results of this study indicate that the closure of the back arc basin led to a crustal thickening event around 420-410 million years ago.
INTERNATIONAL GEOLOGY REVIEW
(2023)
Article
Geosciences, Multidisciplinary
Bo Zhou, Yunpeng Dong, Zhao Yang, Johann Genser, Franz Neubauer, Dengfeng He, Bo Hui, Xiaohui Shi
Summary: Geochronological dating of detrital minerals from sedimentary rocks can provide valuable records of the erosional and unroofing history of orogenic systems. This study used detrital U-Pb zircon and 40Ar/39Ar muscovite dating to investigate the thermal and erosional evolution of the East Kunlun Orogenic Belt during the Mesozoic. The results suggest that the E-KOB was the major source for Triassic and Jurassic strata in the southern East Kunlun region.
GEOLOGICAL JOURNAL
(2022)
Article
Geosciences, Multidisciplinary
Dengfeng He, Yunpeng Dong, Christoph A. Hauzenberger, Shengsi Sun, Xiaoming Liu, Yuangang Yue
Summary: The Qingshuiquan mafic granulite in the East Kunlun orogenic belt, northern Tibetan Plateau, has been studied in terms of its geochemistry, geochronology, mineralogy, and phase modeling. The findings reveal the mineral assemblage generations, pressure-temperature path, and the protolith origin of the mafic granulite. This contributes to a better understanding of the tectonic architecture and evolutionary history of the orogenic belt.
GEOLOGICAL SOCIETY OF AMERICA BULLETIN
(2023)
Article
Geology
Le Zhang, Wei Li, Dazhi Jiang, Yunpeng Dong, Li Liang, Wenbin Kang, Jinxiang Zhao, Liuqing Jiang, Falak Sheir
Summary: The Qinling Orogenic Belt was formed through convergence and collision between the North China Block and South China Block during the Palaeozoic to Late Triassic. The exact termination time of the Late Mesozoic contractional deformation and the transformation from compression to extension remains unclear. However, the extensional shear zone in the West Qinling Orogenic Belt provides important clues to understanding the tectonic transformation and uplift of the orogenic belt. This study focuses on the kinematics, deformation temperature, and geochronology of the shear zone, revealing that it formed under high greenschist-low amphibolite facies conditions and occurred around 120-113 Ma. The extensional collapse of the Qinling Orogenic Belt during the Late Cretaceous led to the rapid uplift and exhumation of the Taibai pluton and the North Qinling Belt in the east.
INTERNATIONAL GEOLOGY REVIEW
(2023)
Article
Geology
Xiang Ren, Yunpeng Dong, Dengfeng He, Shengsi Sun, Bin Zhang, Bo Zhou, Bo Hui, Yuangang Yue
Summary: This study presents new results on the Xidatan pluton in the southern East Kunlun Orogenic Belt. The study reveals that the pluton is composed of quartz monzodiorite, host monzogranite, and igneous microgranular enclaves. The results suggest a common magma source for the quartz monzodiorite and IMEs, and a possible origin of the host monzogranite from partial melting of lower crustal mafic rocks.
INTERNATIONAL GEOLOGY REVIEW
(2023)
Article
Geosciences, Multidisciplinary
Kai Weng, Yunpeng Dong, Liuqing Jiang, Zhongping Ma, Shuangshuang Wang, Bo Chen
Summary: The Altai region of China is rich in granite resources, which can be used to understand the geological history of the area. Through various analyses, we found that the granitoids in the region have different ages and tectonic origins. The gneissic granites formed in the Ordovician period through volcanic magmas extracted from the mantle wedge. The syenogranites in the Devonian period originated from volcanic magmas in a back-arc basin. The diorites in the Permian period were derived from a mixed source involving oceanic crust and lithospheric mantle. The two-mica monzonitic granites and muscovite granites formed through crustal recycling and anatexis of ancient metasedimentary rocks. By combining these findings with previous data, we propose a tectonic evolution sequence in the Altai region, involving continental arc magmatism, back-arc extension, and arc-arc collision.
JOURNAL OF THE GEOLOGICAL SOCIETY
(2023)
Article
Geosciences, Multidisciplinary
Jiali You, Zhao Yang, Xiaohui Shi, Chuanbo Shen, Yunpeng Dong, Bin Cheng
Summary: The Daba Shan orocline, located in the northeastern margin of the Sichuan Basin, is believed to be a foreland thrust-fold belt of the Qinling Orogen since the Late Triassic. Understanding the exhumation history of the rocks is crucial to determine the development of this orocline structure. Detrital apatite fission-track dating of modern river sands reveals the regional exhumation history of the Daba Shan orocline, showing four age peaks that can be attributed to tectonic exhumation.
JOURNAL OF EARTH SCIENCE
(2023)
Article
Geography, Physical
A. Securo, C. Del Gobbo, L. Rettig, S. Pillon, A. De Luca, D. Fontana, E. Benedetti Fasil, R. R. Colucci
Summary: Small glaciers in temperate mountain regions have experienced significant reduction and unprecedented melt rates in recent years. Some glaciers have transitioned from clean ice to debris-covered or even rock glaciers. This study examines the surface elevation change of the Popera Alto glacier in the Sesto Dolomites using LiDAR and Structure from Motion surveys, and analyzes its evolution in terms of surface cover and geomorphic processes. The glacier has lost an average of 0.35 m water equivalent per year over the past 16 years, with active modification of its surface cover by geomorphic processes. The role of debris and local topography feedback has allowed the resilience of the glacier, leading to a marked difference between the current environmental equilibrium line altitude (envELA) and the effective ELA (effELA) of the glacier.
Article
Geography, Physical
Zhenzhen Yan, Yaolin Shi, Lili Kang, Xiangtao Fan
Summary: This study proposes a quantitative regional deformation model based on global positioning system (GPS) data to quantitatively analyze the morphological evolution of rivers in the Three Rivers Region. It finds that tectonic deformation phases significantly control regional landscape development and drainage features.
Article
Geography, Physical
Said Mukhtar Ahmad, Nitheshnirmal Sadhasivam, Mona Lisa, Luigi Lombardo, Mustafa Kemal Emil, Amira Zaki, Cees J. Van Westen, Islam Fadel, Hakan Tanyas
Summary: In this study, we investigated a large slow-moving landslide in Northern Pakistan, using Interferometric Synthetic Aperture Radar (InSAR) analysis. Our results showed that the crown of the landslide is moving faster than the surrounding regions, while the footslope experienced high deformations. We discussed the possible roles of meteorologic and anthropogenic factors in causing these deformations.
Article
Geography, Physical
Shuang Bian, Xibin Tan, Yiduo Liu, Suoya Fan, Junfeng Gong, Chao Zhou, Feng Shi, Michael A. Murphy
Summary: The Yarlung River's drainage divide is primarily moving north due to variations in precipitation across the Himalayas. The Gangdese drainage divide shows predominantly northward and southward migration, controlled by base-level rise and downstream influences. The presence of north-trending rifts separates the drainage divides into five zones, each with a distinct migration pattern.
Article
Geography, Physical
Joon-Young Park, Seok Yoon, Deuk-Hwan Lee, Seung-Rae Lee, Hwan-Hui Lim
Summary: This study developed a multiple-regression model to estimate site-specific average growth rates of debris flow events. The proposed model was validated through a case study and showed reasonable predictions of debris flow velocities and heights.
Article
Geography, Physical
Nicholas Reilly Mccarroll, Arnaud Temme
Summary: New geochronological data from hillslope boulder armor in the Flint Hills reveal the rates and timing of lateral retreat in the landscape. Surfaces of limestone boulders dating back to the Pleistocene era were found, and the ages of the hillslope armor increased with distance from the limestone bench. The estimated rate of lateral retreat in this landscape is 0.02 mm/yr.
Article
Geography, Physical
Xinbo Yao, Yuntao Tian
Summary: By studying the Longmenshan-Minshan drainage divide, we found that it has reached a dynamic steady state, indicating a balance between erosion and rock uplift. This study also reveals the process of formation and evolution of the divide and raises questions about the effectiveness of divide migration metrics.
Article
Geography, Physical
Junhui Yu, Pin Yan, Yanlin Wang, Guangjian Zhong, Changliang Chen
Summary: The seafloor mounds in the Chaoshan Depression of the South China Sea are identified as mud volcanoes, with fluids coming from underlying mud-fluid diapirs. The hydrocarbon gases feeding the mud volcanoes and diapirs are reasoned to originate from deep Mesozoic source rocks, indicating significant Mesozoic hydrocarbon potential in the Chaoshan Depression.
Article
Geography, Physical
Marius Huber, Luc Scholtes, Jerome Lave
Summary: This paper investigates the relationships between hillslope stability and fabric anisotropy of brittle rock materials and the implications for landscape shaping. It explores the different stability modes and movement characteristics of anisotropic materials, and demonstrates the significant control of material anisotropy on landscape shaping.
Article
Geography, Physical
Shubhra Sharma, Anil D. Shukla
Summary: The study investigates the relationship between glacial dynamics and lake sedimentation during the mid-Holocene climate variability in the Southern Zanskar ranges. It utilizes geomorphological disposition, elemental geochemistry, and optical chronology of relict lake sediment to reconstruct the pattern of minor glacier responses to climate variability. The results indicate six centennial to millennial-scale climatic phases, with warmer phases represented by decreased mineralogical fine grain flux and increased coarse grain flux. The study highlights the potential of relict lake sediment and para/peri-glacial landforms in understanding glacial dynamics and climate change during the Holocene.
Article
Geography, Physical
Jean-Francois Bernier, Sydney W. Meury, Patrick Lajeunesse
Summary: In this study, an approach combining various data and observation methods was proposed to improve the monitoring of landfast ice dynamics and its geomorphic impact on sedimentary systems. The results demonstrate the ability of the approach to accurately measure interannual variations in landfast ice and constrain geomorphic changes. Additionally, the study found a strong relationship between the severity of freezing seasons and the response of landfast ice to hydrometeorological events, with different geomorphic responses observed under different winter conditions.
Article
Geography, Physical
Heping Shu, Fanyu Zhang
Summary: This study investigates the relationship between susceptibility of soil-water hazards and human activities, geoheritage sites in the Loess Plateau, China. Landslide and gully erosion susceptibility were obtained using gradient boosting and support vector machines, and a hazard matrix was formed to couple landslide and gully erosion susceptibility. The study found different trends in the magnification times of soil-water hazards chain under different scenarios.
Article
Geography, Physical
Guangqiang Qian, Zhuanling Yang, Xuegang Xing, Zhibao Dong, Youyuan Guo
Summary: Granule ripples are aeolian landforms armored against erosion by coarse grains. This study investigates their seasonal morphological evolution and migration in the Sanlongsha Dune Field. The findings show that wind events, especially those exceeding the threshold velocities of coarse grains, significantly influence the morphodynamics of granule ripples. The study highlights the importance of considering the reptation and saltation of coarse grains in future research on granule ripples.