Geoheritage values of one of the largest maar craters in the Arabian Peninsula: the Al Wahbah Crater and other volcanoes (Harrat Kishb, Saudi Arabia)     

Mohammed R. Moufti  Károly Németh  Nabil El-Masry  Atef Qaddah 《Central European Journal of Geosciences》2013,5(2):254-271

Al Wahbah Crater is one of the largest and deepest Quaternary maar craters in the Arabian Peninsula. It is NW-SE-elongated, ～2.3 km wide, ～250 m deep and surrounded by an irregular near-perpendicular crater wall cut deeply into the Proterozoic diorite basement. Very few scientific studies have been conducted on this unique site, especially in respect to understanding the associated volcanic eruption processes. Al Wahbah and adjacent large explosion craters are currently a research subject in an international project, Volcanic Risk in Saudi Arabia (VORiSA). The focus of VORiSA is to characterise the volcanic hazards and eruption mechanisms of the vast volcanic fields in Western Saudi Arabia, while also defining the unique volcanic features of this region for use in future geoconservation, geoeducation and geotourism projects. Al Wahbah is inferred to be a maar crater that formed due to an explosive interaction of magma and water. The crater is surrounded by a tephra ring that consists predominantly of base surge deposits accumulated over a pre-maar scoria cone and underlying multiple lava flow units. The tephra ring acted as an obstacle against younger lava flows that were diverted along the margin of the tephra ring creating unique lava flow surface textures that recorded inflation and deflation processes along the margin of the post-maar lava flow. Al Wahbah is a unique geological feature that is not only a dramatic landform but also a site that can promote our understanding of complex phreatomagmatic monogenetic volcanism. The complex geological features perfectly preserved at Al Wahbah makes this site as an excellent geotope and a potential centre of geoeducation programs that could lead to the establishment of a geopark in the broader area at the Kishb Volcanic Field.  相似文献   

Application of a revised hydrostratigraphical classification and nomenclature to the Mesozoic and Cenozoic succession of Saudi Arabia   总被引：1，自引：0，他引：1  

Abdulaziz M. Al-Bassam  Mohammed E. Al-Dabbagh  Mohammed Tahir Hussein 《Journal of African Earth Sciences》2000,30(4):917

At the dawn of the 21st century many parts of the world are suffering a shortage of water resources. Arid and semi-arid areas in particular are facing challenges and increasing pressure is being put on their groundwater management plans. Such a situation created an urgent need to put forward a design for classification and nomenclature that can help to differentiate highly productive zones from small locally exploited productive zones. A previously proposed hydrostratigraphical classification and nomenclature scheme is revised, modified, and applied to the Mesozoic-Cenozoic sedimentary succession of Saudi Arabia. The scheme utilised in the present paper is modified to include, in addition, productivity, water quality criteria, usability, and recharge as criteria reflecting the hydrogeological importance of the productive zones.The Triassic Sudair Mega-aquitard forms the lower hydrostratigraphic boundary for the Ad-Dahna'a Aquasystem. The Ad-Dahna'a Aquasystem comprises two aquagroups: the Riyadh and Rub'Al-Khali Aquagroups. Each aquagroup is in turn subdivided into superaquifers, aquifers and possibly subaquifers, separated by aquitards of different ranks. The physical and hydrogeological characteristics of each unit are also discussed.  相似文献   

Stratigraphy of multiple piston-core sediments for the last 30,000 years from Lake Biwa, Japan     

Keiji Takemura  Akira Hayashida  Makoto Okamura  Hiromi Matsuoka  Mohammed Ali  Mohammed Ali  Yoshiki Kuniko  Masayuki Torii  Masayuki Torii 《Journal of Paleolimnology》2000,23(2):185-199

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Slope stability FEM analysis and retaining wall design: a case study of clinker in Benxi of Liaoning     

Aref M. O. AL-JABALI  Lei NIE  Jianlei LIU  Huangping DING  Nengjuan ZHOU  Mohammed HAZAEA 《世界地质(英文版)》2008,11(2)

Stability is always the most important problem after high slope was excavated. The study analyzed the stress and strain inside the slope by Finite Element Method (FEM) and carried through stress distribution and failure zone, then analyzed the stability of the slope using three different methods and came to the conclusion that it is in unstable condition, so the designed retaining wall was put forward which makes the slope stable.  相似文献   

Book reviews     

T. Littmann  Rudolf Brázdil  Manfred Domrös  Mohammed A. Kishk  A. Wallner  Radan Květ  Andreas Grotewold 《GeoJournal》1992,26(4):547-549

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The marine killers: Dinoflagellates in estaurine and coastal waters     

Shoukri N. Messieh  Mohammed I. El-Sabh 《Natural Hazards》1984,3(1):69-86

Records of massive fish kills and paralytic shellfish poisoning (PSP) in Europe and North America go back to the 17th century. But, it was not until the 1940s when the relationship between PSP, red tide and toxic dinoflagellateGonyaulax was established. Recent records show that PSP and related poisons caused by toxic dinoflagellates in coastal waters and estuaries, are a world-wide problem. Diarrhetic shellfish poisoning (DSP) and neurotoxic poisoning (NSP), believed earlier as bacterial or viral infections are now shown to be caused by other toxic dinoflagellates such asDinophysis. The shellfish most often involved in the poisoning are mussels and clams. Other dinoflagellates,Gyrodinium, occasionally cause massive fish kills in vast coastal areas, resulting in fishery and economic losses.Factors promoting toxic dinoflagellate bloom development and PSP/DSP outbreaks are not fully understood. In previous studies, temperature was considered as the principal factor influencing dinoflagellate blooming. Recent studies showed that other factors such as salinity, sunlight, freshwater runoff and water stability are also important. Pollution from land drainage and sewage discharge in inshore waters were also implicated.Current knowledge indicates that although chemical and biotic factors are important forin-situ growth of dinoflagellate cells, convergence by thermal and tidal fronts is essential for cell accumulation and bloom development. Advances in physical oceanographic research, modelling and remote sensing enabled the detection of fronts and bordering eddies with high precision. There is a potential for an increased use of these technological advances in predicting and monitoring the bloom development.The present paper overviews the history and distribution of toxic dinoflagellates, and the physical factors influencing bloom development and PSP/DSP outbreaks. Future research needs to improve the predictability and control of this world-wide hazard are also discussed.  相似文献   

"The orientation of helical flow in curved channels" by Corney et al., Sedimentology, Vol. 53, pp. 249–257 – discussion     

Jasim Imran  Mohammad Ashraful Islam  Ahmed Kassem 《Sedimentology》2008,55(1):235-239

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Foreword     

Mohammed Bensaid 《International Journal of Earth Sciences》1992,81(1):I-I

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Dynamics of particle creation in relativistic viscous fluid Universe in Brans Dicke theory     

L. Ibochouba  Mohammed Ashraf Ali 《Astrophysics and Space Science》1996,241(2):227-235

The study of dynamics of the particle creation in relativistic viscous fluid in Robertson-Walker Universe is studied by using Brans-Dicke theory. The behaviour of these solutions with respect to Dirac's hypothesis are investigated along with the discussion of the physical parameters as well as the variable gravitational constant. By adopting a particular method of integration, exact solutions are obtained and physical interpretations are presented.  相似文献   

Optical and radiative properties of aerosols over Abu Dhabi in the United Arab Emirates     

S Naseema Beegum  Haifa Ben Romdhane  Mohammed Tauha Ali  Peter Armstrong  Hosni Ghedira 《Journal of Earth System Science》2016,125(8):1579-1602

The present study is on the aerosol optical and radiative properties in the short-wave radiation and its climate implications at the arid city of Abu Dhabi (24.42 ^°N, 54.61 ^°E, 4.5 m MSL), in the United Arab Emirates. The direct aerosol radiative forcings (ARF) in the short-wave region at the top (TOA) and bottom of the atmosphere (BOA) are estimated using a hybrid approach, making use of discrete ordinate radiative transfer method in conjunction with the short-wave flux and spectral aerosol optical depth (AOD) measurements, over a period of 3 years (June 2012–July 2015), at Abu Dhabi located at the south-west coast of the Arabian Gulf. The inferred microphysical properties of aerosols at the measurement site indicate strong seasonal variations from the dominance of coarse mode mineral dust aerosols during spring (March–May) and summer (June–September), to the abundance of fine/accumulation mode aerosols mainly from combustion of fossil-fuel and bio-fuel during autumn (October–November) and winter (December–February) seasons. The monthly mean diurnally averaged ARF at the BOA (TOA) varies from ?13.2 Wm^?2 (～?0.96 Wm^?2) in November to ?39.4 Wm^?2 (?11.4 Wm^?2) in August with higher magnitudes of the forcing values during spring/summer seasons and lower values during autumn/winter seasons. The atmospheric aerosol forcing varies from + 12.2 Wm^?2 (November) to 28.2 Wm^?2 (June) with higher values throughout the spring and summer seasons, suggesting the importance of mineral dust aerosols towards the solar dimming. Seasonally, highest values of the forcing efficiency at the surface are observed in spring (?85.0 ± 4.1 W m^?2 τ ^?1) followed closely by winter (?79.2 ± 7.1 W m^?2 τ ^?1) and the lowest values during autumn season (?54 ± 4.3 W m^?2 τ ^?1). The study concludes with the variations of the atmospheric heating rates induced by the forcing. Highest heating rate is observed in June (0.39 K day ^?1) and the lowest in November (0.17 K day ^?1) and the temporal variability of this parameter is linearly associated with the aerosol absorption index.  相似文献