Role of science and independent research during volcanic eruptions     

Dennis Geist  Michael O. Garcia 《Bulletin of Volcanology》2000,62(1):59-61

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Deep soil water dynamics in an undisturbed primary forest in central Amazonia: Differences between normal years and the 2005 drought   总被引：1，自引：0，他引：1       下载免费PDF全文

Elisângela Broedel  Javier Tomasella  Luiz Antônio Cândido  Celso von Randow 《水文研究》2017,31(9):1749-1759

Understanding how Amazonian rainforests deal with extended droughts is critical in the face of changing climate. This research analyze the physical properties and the soil water dynamics of a deep soil profile in an area of primary forest in central Amazonia to elucidate these processes under drought and nondrought conditions. Physical soil properties derived from soil cores exhibited a distinctive layer between 480 and 880 cm deep, characterized by higher microporosity and low plant water availability. In situ soil moisture measurements collected during the period from January 2003 through February 2006 and for depths ranging from 10 to 1,430 cm suggest that, in the study site, the top 480 cm of the soil profile satisfied most of the transpirational demands in normal climatological years. However, during exceptionally dry periods, such as the 2005 drought, root uptake occurs below 480 cm. As concluded by previous studies, most of the uptake is concentrated in the first meter of the soil profile: More than 40% of the total demand for transpiration is supplied by the top meter of soil. Because deep root uptake occurred at greater depths than normal during the 2005 drought, our results suggest that this is a fundamental mechanism to cope with prolonged droughts.  相似文献   

Improving reservoir description by using geostatistical and multivariate data analysis techniques     

Henrique Garcia Pereira  António Costa e Silva  Amilcar Soares  Luis Ribeiro  Justino de Carvalho 《Mathematical Geosciences》1990,22(8):879-913

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Evolution of alkalic lavas at Haleakala Volcano,east Maui,Hawaii     

C. -Y. Chen  F. A. Frey  M. O. Garcia 《Contributions to Mineralogy and Petrology》1990,105(2):197-218

The postshield and posterosional stages of Haleakala Volcano contain intercalated alkalic basalt and evolved alkalic lavas. Isotopic and incompatible element abundance ratios in the Haleakala postshield basalts changed systematically with time, providing evidence for significant temporal changes in the mantle components contributing to the magmatic sources. Specifically, a depleted, i.e. low⁸⁷Sr/⁸⁶Sr and high¹⁴³Nd/¹⁴⁴Nd, mantle component is more abundant in younger lavas. However, as magma-production rates decreased during the postshield and posterosional stages, basaltic melts in magma reservoirs cooled and fractionated, leading to evolved residual melts such as hawaiite. Because primary basalt compositions changed with time, the evolved Haleakala lavas formed from a range of parental compositions. However, basalts and evolved lavas of similar age and isotopic ratios (Sr and Nd) have major and trace element contents that are consistent with a crystal-fractionation model. Although alkalic basalt and hawaiite are the dominant lavas of the postshield stages of both Haleakala and Mauna Kea volcanoes, there are important differences between their lavas. For example, compositional differences between the hawaiite suites at Haleakala and Mauna Kea indicate that, on average, the evolved lavas at Haleakala formed at lower pressures. Also, at Haleakala basalts are intercalated with hawaiites, whereas at Mauna Kea basalts and hawaiites are separated by a sharp boundary. These differences probably reflect a higher magma supply rate to the Haleakala volcano.  相似文献   

INTERPRETING THE LARGE LIMB ERUPTION OF JULY 9, 1982     

Jordan  Stuart  Garcia  Adriana  Bumba  Vaclav 《Solar physics》1997,173(2):359-376

A time series of K3 spectroheliograms taken at the Coimbra Observatory exhibits an erupting loop on the east limb on July 9, 1982 in active region NOAA 3804. The Goddard SMM Hard X-Ray Burst Spectrometer (HXRBS) observations taken during this period reveal a hard X-ray flare occurring just before the loop eruption is observed, and SMS-GOES soft X-ray observations reveal a strong long-duration event (LDE) following the impulsive phase of the flare. A Solwind coronagram exhibits a powerful coronal mass ejection (CME) associated with the erupting loop. H flare and prominence observations as well as centimeter and decimeter radio observations of the event are also reviewed. A large, north–south-oriented quiescent prominence reported within the upper part of the CME expansion region may play a role in the eruption as well. The spatial and temporal correlations among these observations are examined in the light of two different current models for prominence eruption and CME activation: (1) The CME is triggered by the observed hard X-ray impulsive flare. (2) The CME is not triggered by a flare, and the observed soft X-ray flare is an LDE due to reconnection within the CME bubble. It is concluded that this event is probably of a mixed type that combines characteristics of models (1) and (2). The July 9 event is then compared to three other energetic CME and flare eruptions associated with the same active-region complex, all occurring in the period July 9 through September 4, 1982. It is noted that these four energetic events coincide with the final evolutionary phase of a long-lasting active-region complex, which is discussed in a companion paper (Bumba, Garcia, and Jordan, 1997). The paper concludes by addressing the solar flare myth controversy in the light of this work.  相似文献   

An assessment of the creep behaviour of Brazilian salt rocks using the multi-mechanism deformation model   总被引：1，自引：1，他引：0  

Pedro A. L. P. Firme  Deane Roehl  Celso Romanel 《Acta Geotechnica》2016,11(6):1445-1463

Salt rocks are geomaterials that exhibit several peculiarities, which require a particular approach in rock mechanics. In the field, those rocks are usually found in layered/bedded deposits and in domes or similar structures. Creep is one of the main deformation mechanisms associated with salt rocks, and this phenomenon is highly dependent on the stress state, temperature and mineralogy. Salt rock mechanics for engineering applications requires the definition of a powerful constitutive model and this is an ongoing challenge. Among the many available models, one of the most sophisticated physical constitutive models for salt rocks is the multi-mechanism deformation creep model (MD model). The main contribution of this work is to present a first effort in the use of the MD model for Brazilian salt rocks. Material-sensitive parameters have been calibrated for the Brazilian halite through two methodologies. Salt is modelled as an elasto-viscoplastic material. Numerical simulations using the finite element method have been carried out for triaxial creep tests, Pre-salt wellbore closure and mining gallery convergence in order to validate the parameter set and the methodologies. Excellent results have been observed in most of the applications for validation. Even so, validation efforts should continue to consolidate the parameters and identify possible limitations.  相似文献   

Near-Surface Effects of Free Atmosphere Stratification in Free Convection     

Juan Pedro Mellado  Chiel C. van Heerwaarden  Jade Rachele Garcia 《Boundary-Layer Meteorology》2016,159(1):69-95

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Decomposition and analysis by atomic absorption photospectrometry of silicate rocks     

J. Saavedra  A.Garcia Sanchez  S.Rodriguez Perez 《Chemical Geology》1974,13(2):135-139

A rapid and simple method of analysis of silicate rocks using gold crucibles and fluoroboric acid as a solvent of the disintegrated material has been developed. The main elements are determined in a single treatment. The results obtained are comparable to the values recommended for samples of eleven standard rocks.  相似文献   

Time series surface-wave recovery from pressure gage     

Hsiang Wang  Dong-Young Lee  Allen Garcia 《Coastal Engineering》1986,10(4)

Recovery of surface-wave time series from pressure gage data is a time-consuming process and is not customarily carried out. Such information is, however, useful particularly in real-time for warning of freak waves or waves of unusual characteristics. Two simple numerical filters are developed here to serve such purpose. The first method is a linear filter with a built-in window to suppress high-frequency noise. The second method recovers the surface wave by computing the local surface curvature. These filters are very simple and can be programmed into a microprocessor to be integrated into field instrument packages.Both filters have been tested satisfactorily against conventional linear filters using simulated wave data and wave data collected in intermediate water depth. Neither filter requires pre-filtering of noise from raw data, which is commonly required to recover surface-wave information from sub-surface pressure data.  相似文献   

Food habits of Dipturus chilensis (Pisces: Rajidae) off Patagonia, Argentina   总被引：1，自引：0，他引：1  

Alonso  M. Koen; Crespo  E. A.; Garcia  N. A.; Pedraza  S. N.; Mariotti  P. A.; Vera  B. Beron; Mora  N. J. 《ICES Journal of Marine Science》2001,58(1):288-297

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