On the fractal dimension of the fallout deposits: A case study of the 79 A.D. Plinian eruption at Mt. Vesuvius

We investigated the existence of a fractal law (power law) distribution of size pyroclastic fragments erupted during the fallout phase of the 79 A.D. Plinian eruption at Mt. Vesuvius. In particular, we performed a particle size distribution analysis on 18 white and grey pumice samples collected in six sites distributed in the SW sector of Mt. Vesuvius. Our measurements show that the fragmentation of samples in the investigated range (from 32 mm to 850 μm) follows a power law, guaranteeing the scale invariance of the process. The relationship frequency-size distribution of the fragments is verified independently from the nature (i.e., pumices and lithics) and stratigraphic height of the considered samples in the pyroclastic deposit. Therefore, the fractal fragmentation theory can be indicated for evaluating the relationship between the intensity of fragmentation (fractal dimension D) and eruption energy. In this way the apparent chaotic distribution of the particles in the fallout deposits hides a self-organized complexity revealed by the retrieved power law distribution. We further remark that a key aspect of our analysis is the founded evidence that the fractal dimension of the lithics is systematically greater than that of the pumices.     

近30年来天山托木尔峰东侧分水岭处冰川变化

利用1978年出版的航测地形图与1976年MSS影像(地形图于20世纪70年代初期测绘)、1990年landsatTM影像、2002年CBERS影像对西天山托木尔峰以东分水岭处的5条冰川近30年来的动态变化进行了研究。研究结果表明,这5条冰川在1970年代初-2002年近30年来整体上处于退缩状态,这与该地区20世纪80、90年代气温升高导致冰雪消融加速而冬季降水量基本稳定即补给来源基本不变的趋势是相符合的。这也表明,在气候变暖的趋势下,该地区冰川的补给-消融动态平衡关系被打破,冰川总体上处于退缩状态。     

Modeling unusual eruptive behavior of Mt. Etna,Italy, by means of event bush

One of the best-studied volcanoes of the world, Mt. Etna in Sicily, repeatedly exhibits eruptive scenarios that depart from the behavior commonly considered typical for this volcano. Episodes of intense explosive activity, pyroclastic flows, dome growth and cone collapse pose a variety of previously underestimated threats to human lives in the summit area of the volcano. However, retrospective analysis of these events shows that they were likely caused by the same very sets of premises and starting conditions as “normal” eruptions, yet combined in an unexpected, probably unique, way. To cope with such unexpected consequences, we involve an approach of artificial intelligence developed specially for needs of the geosciences, the event bush. Scenarios inferred from the event bush fit the observed ones and allow to foresee other low-probability events that may occur at the volcano. Application of the event bush provides a more impartial vision of volcanic phenomena and may serve as an intermediary between expert knowledge and numerical assessment, e.g., by means of Bayesian Belief Networks.     

小五台山亚高山景观尺度水热条件与植被关系

以河北省小五台山为研究区,通过转化糖方法获取亚高山不同景观部位效应温度,结合DEM模型模拟研究区内太阳直接辐射以及土壤湿润度系数,进而构建生境干燥度指数。以此为基础,在景观尺度上定量分析研究区内亚高山带水热条件与森林和亚高山草甸植被分布格局的关系。结果表明,① 研究区域中森林分布地段生境的太阳直接辐射,效应温度和干燥度指数都显著低于草甸分布地段,土壤水分系数则恰恰相反;② 综合太阳直接辐射或效应温度与土壤湿润度系数的干燥度指数统计分析结果,优于分别以各个因子单独进行分析的结果;③ 在植被格局的形成中,干燥度起着至关重要的作用,这与在水平地带中,森林与草原植被的分布格局受干燥度控制的规律相一致。     

The carbon accumulation and dissipation features of sub—alpine woodland in Mt.Gongga

Based on biomass investigations,soil respiration and plant photosynthesis measurement of dominant trees in Hailuogou valley of Mt.Gongga,Southwest China,the carbon(C) storage,absorption and release for several typical woodlands in sub-alpine zones have been discussed.For Abies fahri forest of 3,000 m above sea level,the Cstorage amount is 177.4t/ha for above-ground biomass and 143.2 t/ha for soil below-ground biomass. The annual gross C fixed by vegetation photosynthesis is 20-24 t/ha. The C release by canopy respiration is 3.0-5.5 t/ha for arbors and 10-19 t/ha for surface soil and roots.The annual net C fixed of forest ecosystem is about 6.0-7.1 t/ha.At lower elevations,the amount of C released by woodlands is higher than that of woods at higher elevations.The C fixed capacity of renewed forest with middle-aged trees is higher than that of mature forest.Before becoming over-matured forest,woodland is an important sink of C whereas bareland in woods is the source of atmospheric C.     

STUDY ON THE ISOTOPIC CHRONOLOGY AND THE TECTONIC SIGNIFICANCE OF DUGUER GRANITIC GNEISS IN CENTRAL QIANGTANG, TIBET

STUDY ON THE ISOTOPIC CHRONOLOGY AND THE TECTONIC SIGNIFICANCE OF DUGUER GRANITIC GNEISS IN CENTRAL QIANGTANG, TIBET     

DEEP SEISMIC SOUNDING EVIDENCE FOR TECTONIC INTERACTION BETWEEN TARIM AND WEST KUNLUN MT

DEEP SEISMIC SOUNDING EVIDENCE FOR TECTONIC INTERACTION BETWEEN TARIM AND WEST KUNLUN MT1　MatteP ,TapponnierP ,ArnaudN ,etal.TectonicofWesternTibet,betweentheTarimandtheIndus[J] .EarthPlanetSciLett,1996 ,14 2 :311～ 330 2　GaoRui,LiDexing,LuDeyuan ,etal.DeepseismicreflectionprofileacrosscontactzoneofwestKunlunandTarimalongtheXinjianggeotransectinNWChina[C] .14 thHKTworkshop ,1999.4 9～ 50 .…     

Recent 200 Years Climatic and Environmental Records From the Far East Rongbuk Ice Core, Mt. Qomolangma(Everest)

RECENT 200 YEARS CLIMATIC AND ENVIRONMENTAL RECORDS FROM THE FAR EAST RONGBUK ICE CORE, MT. QOMOLANGMA (EVEREST)     

A WIMP detector with two-phase xenon

We describe an important new technique to search for WIMPs. This technique employs a method of background discrimination using double phase xenon as detector target. We describe the construction of a two-phase, 1-kg xenon detector. The detector will be installed at the underground laboratory in the Mt. Blanc tunnel, which provides a low background rate. A comparison between the sensitivity curve of our detector and the theoretical events limit from SUSY calculations is presented.     

五台山区太古宙/元古宙界线划分及其地球演化意义

太古宙/元古宙界线代表地球演化历史上的重大事件,如何准确标定和划分这一界线对认识早期演化历史具有重要意义。区域构造及同位素地质年代学研究表明,华北克拉通新太古代构造演化明显滞后于欧美澳等克拉通,成为有利于建立太古宙/元古宙界线的关键地区。山西五台山区保留了较完整的新太古代-古元古代地层记录。先前研究主要依据该区地层、区域构造、叠层石记录进行界线划分,并对界线争议较多。本文在五台山区长期野外研究的基础上,通过对磨拉石沉积、同构造花岗岩、裂解环境相关玄武岩的综合探讨,建议这一界线划分在东冶亚群与豆村亚群之间。初步的同位素年龄制约表明,这一界线的时代介于2549±22Ma到2450±10Ma之间,与早期大陆克拉通伸展裂解、隆升剥蚀相关,并涉及岩石圈、水圈、大气圈性质的重大变化。