Frequency and duration of historical droughts from the 16th to the 19th centuries in the Mexican Maya lands, Yucatan Peninsula     

Blanca Mendoza  Virginia García-Acosta  Victor Velasco  Ernesto Jáuregui  Rosa Díaz-Sandoval 《Climatic change》2007,83(1-2):151-168

Using unprecedented catalogues of past severe drought data for the Yucatan Peninsula between 1502 and 1900 coming from historical written documentation, we identified five conspicuous time lapses with no droughts between 1577–1647, 1662–1724, 1728–1764, 1774–1799 and 1855–1880, as well as time epochs with most frequent droughts between 1800 and 1850. Moreover, the most prominent periodicity of the historical drought time series was that of ∼40 years. Using the Palmer Drought Severity Index for the Yucatan Peninsula for the period 1921–1987 we found prominent negative phases between ∼1942–1946 and 1949–1952, 1923–1924, 1928–1929, 1935–1936, 1962–1963, 1971–1972 and 1986–1987. Two prominent periodicities clearly appear at ∼5 and 10 years. Most modern and historical severe droughts lasted 1 year, and share a quasi-decadal frequency. Also, in the first 66 years of the twentieth century the frequency of occurrence of severe drought has been lower compared with the nineteenth century. Some of the major effects and impacts of the most severe droughts in the Yucatan region are examined. We also studied the relation between historical and modern droughts and several large scale climate phenomena represented by the Atlantic Multidecadal Oscillation (AMO) and the Southern Oscillation Index (SOI). Our results indicate that historical droughts and the cold phase of the AMO coincide, while the influence of the SOI is less clear. The strongest coherence between historical droughts and AMO occurred at periodicities of ∼40 years. For modern droughts the coherence of a drought indicator (the Palmer Drought Severity Index) is similar with AMO and SOI, although it seems more sustained with the AMO. They are strongest at ∼10 years and very clearly with the AMO cold phase. Concerning the solar activity proxies and historical droughts, the coherence with a record of beryllium isotope Be¹⁰, which is a good proxy of cosmic rays, is higher than with Total Solar Irradiance. We notice that the strongest coherence between historical droughts and Be¹⁰ occurs at periods ∼60–64 years. When studying modern droughts and solar activity, frequencies of ∼8 years appear, and the coherences are similar for both sunspots and cosmic rays. Comparing natural terrestrial and solar phenomena, we found that the most sustained and strongest modulation of historical drought occurrence is at ∼60–64 years and is between the historical drought series and the solar proxy Be¹⁰. For modern droughts we notice that the coherence is similar among AMO, SOI and the solar indices. We can conclude that the sea surface temperatures (AMO) and solar activity leave their signal in terms of severe droughts in the Maya lands, however in the long term, the influence of the SOI on this type of phenomenon is less clear.  相似文献   

Scientific Errors in the Fearnside Comments on Greenhouse Gas Emissions (GHG) from Hydroelectric Dams and Response to His Political Claiming   总被引：1，自引：0，他引：1  

Luiz Pinguelli Rosa  Marco Aurélio Dos Santos  Bohdan Matvienko  Elizabeth Sikar  Ednaldo Oliveira Dos Santos 《Climatic change》2006,75(1-2):91-102

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Residence and redistribution of REE, Y, Zr, Th and U during granulite-facies metamorphism: behaviour of accessory and major phases in peraluminous granulites of central Spain     

C. Villaseca  C. Martí  n Romera  J. De la Rosa  L. Barbero 《Chemical Geology》2003,200(3-4):293-323

Accessory minerals are thought to play a key role in controlling the behaviour of certain trace elements such as REE, Y, Zr, Th and U during crustal melting processes under high-grade metamorphic conditions. Although this is probably the case at middle crustal levels, when a comparison is made with granulite-facies lower crustal levels, differences are seen in trace element behaviour between accessory minerals and some major phases. Such a comparison can be made in Central Spain where two granulite-facies terranes have equilibrated under slightly different metamorphic conditions and where lower crustal xenoliths are also found. Differences in texture and chemical composition between accessory phases found in leucosomes and leucogranites and those of melanosomes and protholiths indicate that most of the accessory minerals in melt-rich migmatites are newly crystallized. This implies that an important redistribution of trace elements occurs during the early stages of granulite-facies metamorphism. In addition, the textural position of the accessory minerals with respect to the major phases is crucial in the redistribution of trace elements when melting proceeds via biotite dehydration melting reactions. In granulitic xenoliths from lower crustal levels, the situation seems to be different, as major minerals show high concentration of certain trace elements, the distribution of which is thus controlled by reactions involving final consumption of Al-Ti-phlogopite. A marked redistribution of HREE–Y–Zr between garnet and xenotime (where present) and zircon, but also of LREE between feldspars (K-feldspar and plagioclase) and monazite, is suggested.  相似文献   

Fault geometries from the space distribution of the 1990–1997 Sannio–Benevento earthquakes: inferences on the active deformation in Southern Apennines     

Giuseppe Vilardo  Rosa Nappi  Palma Petti  Guido Ventura 《Tectonophysics》2003,363(3-4):259-271

In this study, we analyze the recent (1990–1997) seismicity that affected the northern sector (Sannio–Benevento area) of the Southern Apennines chain. We applied the Best Estimate Method (BEM), which collapses hypocentral clouds, to the events of low energy (M_{d max}=4.1) seismic sequences in order to constrain the location and geometry of the seismogenetic structures. The results indicate that earthquakes aligned along three main structures: two sub-parallel structures striking NW–SE (1990–1992, Benevento sequence) and one structure striking NE–SW (1997, Sannio sequence). The southernmost NW–SE structure, which dips towards NE, overlies the fault that is likely to be responsible for a larger historical earthquake (I_{o max}=XI MCS, 1688 earthquake). The northernmost NW–SE striking structure dips towards SW. The NE–SW striking structure is sub-vertical and it is located at the northern tip of the fault segment supposed to be responsible for the 1688 earthquake. The spatio-temporal evolution of the 1990–1997 seismicity indicates a progressive migration from SE (Benevento) to NW (Sannio) associated to a deepening of hypocenters (i.e., from about 5 to 12 km). Hypocenters cluster at the interface between the major structural discontinuities (e.g., pre-existing thrust surfaces) or within higher rigidity layers (e.g., the Apulia carbonates). Available focal mechanisms from earthquakes occurred on the recognized NW–SE and NE–SW faults are consistent with dip-slip normal solutions. This evidences the occurrence of coexisting NW–SE and NE–SW extensions in Southern Apennines.  相似文献   

Inorganic Water Quality Monitoring Using Specific Conductance in Mexico     

Luis E. Marín  B. Steinich  Oscar Escolero  Rosa María Leal  Braulio Silva  Susana Gutierrez 《Ground Water Monitoring & Remediation》1998,18(1):156-162

Five inorganic geochemical data sets with ion balances less than or equal to 5% (for different hydrogeologic basins in Mexico) were used to construct specific conductance (SC) vs. total dissolved solids (TDS) curves for each aquifer. These curves allow one to proxy the specific conductance for inorganic water quality. The data from these five curves were integrated to form a "global" curve for Mexico. The equation that defines the line is SC = 1.40 TDS + 18. We propose that, in addition to allowing ground water monitoring, establishing a SC vs. TDS curve may be implemented to monitor drinking water supplies such as wells and reservoirs. If anomalously high values are observed, this would warrant detailed geochemical sampling.  相似文献   

Characteristics of Valadares Island aquifer,Paranaguá coastal plain,Brazil     

Suresh D. Babu  E. Hindi  E. da Rosa Filho  A. Bittencourt 《Environmental Geology》2002,41(8):954-959

. Aquifer characterization in terms of geologic–geomorphological considerations, pumping test and hydrochemistry has been carried out to evaluate the groundwater potential of one of the delicate coastal island systems in Parana State, Brazil. The Valadares Island, lying in the Atlantic coastal zone, represents a stabilized beach ridge having a thickness of more than 20 m unconsolidated quartz-rich sand. Field and laboratory investigations suggest that this homogeneous coastal aquifer can partially meet the local domestic demand of fresh water even though it is in hydraulic continuity with the estuarine and tidal systems of Paranaguá bay. Efficiency of the aquifer to hold and release water was determined by conducting a pumping test in one of the partially penetrating wells in the island for 24 h. The physical, chemical and biological analyses of samples from 12 5-cm diameter wells of the area have indicated that groundwater needs purification for drinking purpose. It is advocated that the groundwater potential of the island aquifer is worth considering for sustained but controlled exploitation.  相似文献   

Paleo-environmental and volcano-tectonic evolution of the southeastern flank of Mt. Etna during the last 225 ka inferred from the volcanic succession of the ‘Timpe’, Acireale, Sicily     

Rosa Anna Corsaro  Marco Neri  Massimo Pompilio   《Journal of Volcanology and Geothermal Research》2002,113(1-2)

The tectonic escarpments locally known as ‘Timpe’ cut a large sector of the eastern flank of Etna, and allow an ancient volcanic succession dating back to 225 ka to be exposed. Geological and volcanological investigations carried out on this succession have allowed us to recognize relevant angular unconformities and volcanic features which are the remnants of eruptive fissures, as well as important changes in the nature, composition and magmatic affinity of the exposed volcanics. In particular, the recognition in the lower part of the succession of important and unequivocal evidence of ancient eruptive fissures led us to propose a local origin for these volcanics and to revise previous interpretations which attributed their westward-dipping to the progressive tectonic tilting of strata. These elements led us to reinterpret the main features of the volcanic activity occurring since 250 ka BP and their relationship with tectonic structures active in the eastern flank of Etna. We propose a complex paleo-environmental and volcano-tectonic evolution of the southeastern flank of Mt. Etna, in which the Timpe fault system played the role of the crustal structure that allowed the rise and eruption of magmas in the above considered time span.  相似文献   

The Role of Nuclear Starbursts in Luminous Infrared Seyfert 2 Galaxies     

Rosa M. González Delgado  Timothy Heckman 《Astrophysics and Space Science》1999,266(1-2):187-192

We present HST (WFPC2 and FOC) images and UV GHRS spectraplus ground-based optical spectra of four Luminous Infrared Galaxies (LIRGs) that have Seyfert 2nuclei (Mrk 477, NGC 7130, NGC 5135 and IC 3639). The data provide direct evidence of the existence of a central nuclearstarburst that dominates the UV and optical light and are dusty and compact. The bolometricluminosity ( 10¹⁰ L) of these starbursts is similar to the estimated bolometric luminosities of their obscured Seyfert 1 nuclei, and thus they contributein the same amount to the overall energetics of these galaxies. An extended work based on ground-based optical spectra of the 20 brightest nuclei known indicate that at least 40%of the Seyfert 2 galaxies harbor a nuclear starburst. The eight Seyfert 2 nuclei thatharbor a starburst are strong IR emitters. This suggests that nuclear starbursts can make a significant contribution or even dominate the UV and optical light of LIRGs.  相似文献   

Oil pollution in the eastern Mediterranean     

Rosa Ravid  O.H. Oren  Josepha Ben-Yosef  Hava Hornung 《Marine pollution bulletin》1985,16(2):81-84

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Geothermal map of Mexico     

Prol-Ledesma Rosa Maria  M. Gerardo Juarez 《Journal of Volcanology and Geothermal Research》1986,28(3-4)

Silica temperatures were calculated for 326 water samples from hot and warm springs located throughout Mexico as an attempt to estimate heat flow. Available heat flow data (Smith, 1974; Smith et al., 1979) for northern Mexico were related to silica temperature data to obtain the appropriate constants for the regional conditions according to Swanberg and Morgan's equation (1979, 1980). The constants obtained are similar to those obtained for the United States, therefore heat flow can be estimated on the basis of silica temperature data. By contouring calculated temperatures a map is obtained where the main geothermal provinces are shown.  相似文献