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1.
Italy has a long-standing tradition of earthquake investi-gations. Seismologists can rely on one of the longest and most detailed records of historical seismic#y, 20 years of homogeneous and reliable instrumental data, systematic and widespread active stress data and a comprehensive database of potential seismogenic sources. Here wed escribe these datasets and discuss how they may help usanticipate the large earthquakes of the future.  相似文献   

2.
The Denver Basin bedrock aquifer system is an important source of water for municipal and agricultural uses in the Denver and Colorado Springs metropolitan areas. The Denver area is one of the fastest growing areas in the United States with a population of 1.2 million in 1960 that has increased to over 2.4 million by 2000. This rapid population growth has produced a corresponding increase in demand for potable water. Historically, the Denver area has relied on surface water, however, in the past 10 years new housing and recreation developments have begun to rely on groundwater from the bedrock aquifers as the surface water is fully appropriated and in short supply.The Denver Basin bedrock aquifer system consists of Tertiary and Cretaceous age sedimentary rocks known as the Dawson, Denver, Arapahoe and Laramie-Fox Hills Aquifers. The number of bedrock wells has increased from 12,000 in 1985 to 33,700 in 2001 and the withdrawal of groundwater has caused water level declines of 76 m. Water level declines for the past 10 years have ranged from 3 to 12 m per year. The groundwater supplies were once thought to last 100 years but there is concern that the groundwater supplies may be essentially depleted in 10 to 15 years in areas on the west side of the basin.Extensive development of the aquifer system has occurred in the last 25 years especially near the center of the basin in Douglas and El Paso Counties where rapid urban growth continues and surface water is lacking. Groundwater is being mined from the aquifer system because the discharge by wells exceeds the rate of recharge. Concern is mounting that increased groundwater withdrawal will cause water level declines, increased costs to withdraw groundwater, reduced well yield, and reduced groundwater storage. As the long-term sustainability of the groundwater resource is in doubt, water managers believe that the life of the Denver Basin aquifers can be extended with artificial recharge, water reuse, restrictions on lawn watering, well permit restrictions and conservation measures.  相似文献   

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Kay L. Booth 《GeoJournal》1993,29(3):299-305
Since the turn of the century, recreation has grown as a motivating force in public land administration. Today, the Department of Conservation manages approximately one third of New Zealand's outdoor recreation resources and has the mandate to foster the use of natural and historic resources for recreation, and to allow their use for tourism (Conservation Act 1987:8). This paper traces the emergence of a recreation perspective within public land administration and examines the development of a recreation philosophy and policy within the Department of Conservation. It suggests future directions for outdoor recreation management in New Zealand.  相似文献   

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Noble gas recharge temperatures (NGTs) and radiocarbon ages were determined for 43 groundwater samples collected in the eastern Espa?ola Basin, New Mexico (USA), to identify mountain-block recharge in waters <10 thousand years (ka) old and to evaluate possible changes in mountain-block recharge over the past ??35?ka. For Holocene samples from the southeastern area, NGTs are dominantly 2?C4° cooler than the measured water-table temperature near the mountain front. Computed minimum mountain-block recharge fractions are dominantly 0.2?C0.5, consistent with previous large mountain-block recharge estimates. NGTs do not display the distinct low during the last glacial maximum observed in other paleorecharge studies; samples recharged 15?C25?ka ago are on average only 1.3° cooler than Holocene samples. Instead, samples with the coldest NGTs were recharged 25?C35?ka ago. A proposed explanation is that higher precipitation rates during the last glacial maximum resulted in a lower mean recharge elevation for the basin, essentially buffering the effect of the lower mean annual air temperature and producing NGTs similar to the Holocene. In the period preceding the last glacial maximum, precipitation rates more like today??s resulted in Holocene-like mountain-block recharge fractions, producing a mean NGT ??5° cooler than the Holocene, as expected.  相似文献   

7.
This article discusses the ways in which community protocols might challenge the dominant discourses that guide environmental law and policy at the local, national and international levels and makes suggestions about the conditions that need to be fulfilled if such a challenge is to be effective. Community protocols have attracted the attention of many scholars as they are recognised in the Convention on Biological Diversity’s Nagoya Protocol. They are argued to hold the potential to achieve fair and equitable benefit-sharing by allowing local community voices to express their customary law, worldviews, and ideas of benefit and development among other things. While much of the existing literature discusses community protocols as legal tools, they are also tools that may challenge the dominant discourses argued to guide environmental law and policy. The article takes up this question on the basis of findings from five original case studies. It is argued that community protocols may challenge dominant discourses by: facilitating and articulating the recognition of local communities and indigenous peoples; providing a source for understanding their worldviews; and by empowering them in the long term. In order to achieve these outcomes, community protocol must be understood as processes and pay attention to legal and political contexts, how communities organise, the role of supporting actors, and the articulation of benefits.  相似文献   

8.
Epochs of changing atmospheric CO2 and seawater CO2–carbonic acid system chemistry and acidification have occurred during the Phanerozoic at various time scales. On the longer geologic time scale, as sea level rose and fell and continental free board decreased and increased, respectively, the riverine fluxes of Ca, Mg, DIC, and total alkalinity to the coastal ocean varied and helped regulate the C chemistry of seawater, but nevertheless there were major epochs of ocean acidification (OA). On the shorter glacial–interglacial time scale from the Last Glacial Maximum (LGM) to late preindustrial time, riverine fluxes of DIC, total alkalinity, and N and P nutrients increased and along with rising sea level, atmospheric PCO2 and temperature led, among other changes, to a slightly deceasing pH of coastal and open ocean waters, and to increasing net ecosystem calcification and decreasing net heterotrophy in coastal ocean waters. From late preindustrial time to the present and projected into the 21st century, human activities, such as fossil fuel and land-use emissions of CO2 to the atmosphere, increasing application of N and P nutrient subsidies and combustion N to the landscape, and sewage discharges of C, N, P have led, and will continue to lead, to significant modifications of coastal ocean waters. The changes include a rapid decline in pH and carbonate saturation state (modern problem of ocean acidification), a shift toward dissolution of carbonate substrates exceeding production, potentially leading to the “demise” of the coral reefs, reversal of the direction of the sea-to-air flux of CO2 and enhanced biological production and burial of organic C, a small sink of anthropogenic CO2, accompanied by a continuous trend toward increasing autotrophy in coastal waters.  相似文献   

9.
The six largest known impact craters of the last 250 Myr(≥70 km in diameter),which are capable of causing significant environmental damage,coincide with four times of recognized extinction events at 36(with 2 craters),66,and 145 Myr ago,and possibly with two provisional extinction events at 168 and215 Myr ago.These impact cratering events are accompanied by layers in the geologic record interpreted as impact ejecta.Chance occurrences of impacts and extinctions can be rejected at confidence levels of99.96%(for 4 impact/extinctions)to 99.99%(for 6 impact/extinctions).These results argue that several extinction events over the last 250 Myr may be related to the effects of large-body impacts.  相似文献   

10.
Two types of enclaves occur in magmatic plutons in Tongling,Anhui.Enclaves of the first type are residuals of metamorphic rocks of high amphibolite facies,and those of the other type are magmatic rocks ranging from monzonitic to dioritic in composition. A combined petrological and mineralogical study has been carried out on the two types of enclaves in order to estimate their forming conditions and analyze their relations to their hosts.so as to have an insight into the material sources of magmatic rocks and associated mineral deposits and give a clue to better understanding the mechanism of magmatism-metallogeny.This leads us to propose a new metallogenic model for strats-bound skarn-type ore deposits associated with a syntectic type of magmatic rocks.The new model can be simply summarized as partial melting of old metamorphic basement rocks at depth and accumulating,differentiating and positioning of magmas to form deep-level and shallow-level magma chambers,follower by mixing of different magmas associated with their crypto-explosion,migration of gas-bearing ore fluids and precipitation of metals in fluids within the magmas.  相似文献   

11.
A 63-cm sediment core documents that the concentrations of nutrients in sediment, such as organic carbon, nitrogen and phosphorous, continually increased during the last century in Longgan Lake, middle reaches of the Yangtze River, China. C/N ratio and δ^13Corg revealed that organic matter in the sediment derived mainly from aquatic and terrestrial sources is a minor contributor. Excess phosphorous is related to human activities marked by utilization of phosphoric fertilizers since 1952 A.D. The increase of δ^13Corg towards the sediment surface, together with increasing of OC and N accumulation, indicated the elevation of lake primary productivity due to excess phosphorous loading caused by utilization of phosphoric fertilizer. The decrease of δ^15N during the primary productivity elevation process, especially after 1952, can be attributed to the discharged of nitrogen with lower δ^15N into the lake.  相似文献   

12.
Due to large deserts on Earth surface a thorough understanding of climate change, landscape evolution and geomorphological processes having occurred in deserts is crucial for Earth System Science. The landscapes in deserts are, however, diverse and different over the globe with regard to their geomorphological nature, human activities and geological histories. In the last decades a great number of efforts have been put to the investigation of the initial timing of the occurrence of arid climate, e. g. in northwestern China. Silty sediments in the downwind directions have been used to deduce the histories of deserts. In general, there is a lack of knowledge about processes and landscapes in Chinese drylands between the initial Miocene silt sedimentation at desert margins and the late Quaternary multiple occurrences of wetter climate with assumed large lakes in many of the deserts in northern China. The geomorphological concept of three primary triggering factors, i.e., the sediment supply, sediment availability and transport capacity of wind, and additionally the underground geology need to be fully considered for a better understanding of the environmental histories of sand seas which should not be viewed as equivalent for deserts because sand seas cover between < 1% and ca. 45% of the desert areas in various continents dependent on a complex interaction between various processes of both exogenous and endogenous origins.  相似文献   

13.
The Tertiary Falcón Basin in northwestern Venezuela has a privileged position in the geodynamic puzzle of northwestern South America, occurring in a region where several major plates (Caribbean, South America and Nazca) and minor lithospheric blocks (Maracaibo, Bonaire and Western Colombia) are interacting. A combination of good exposures due to aridity and a near-continuous sedimentary record in a now inverted basin helps to unravel the Neogene and Quaternary geodynamic evolution of this region. A neotectonic and microtectonic investigation of the Plio-Quaternary sedimentary rocks of the northern Falcón Basin reveals that this region is subject to a compressive to transpressive regime at present. This regime is characterized by a NNW–SSE oriented maximum horizontal stress, and a ENE–WSW trending intermediate (or minimum) horizontal stress, as is confirmed by focal mechanism solutions. This stress field is in agreement both with the NNE-directed extrusion of the Maracaibo and Bonaire blocks in Western Venezuela, where the Falcón Basin is located, and present-day transpression along the Caribbean-South America plate boundary zone.  相似文献   

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15.
Well-preserved and abundant Jurassic–Early Cretaceous palynomorph assemblages were recorded from the Kabrit-1 well, north Eastern Desert, Egypt. Thirty-one rock-cutting samples were analyzed and six rock units were differentiated. Seventy-one palynomorph species were identified from the productive samples. Six palynozones were differentiated, and they covered all the studied succession except for a palynomorph barren interval present in the uppermost part. These palynozones arranged in ascending order are as follows: two palynozones were recorded from the Middle-Upper Jurassic (Gonyaulacysta jurassicaLithodinia jurassica Assemblage Zone and Klukisporites pseudoreticulatus- Systematophora penicillata – Escharisphaeridia pocockii Assemblage Zone) and the other four palynozones characterize the Lower Cretaceous deposits (Pilosisporites trichopapillosus – Cribroperidinium orthoceras Assemblage Zone; Dicheiropollis etruscus Interval Zone; Murospora florida – Afropollis operculatus Assemblage Zone and Afropollis jardinus Range Zone). We infer open marine conditions during deposition of the lower part of the Khalig El Ayoun Formation (Oxfordian-Kimmeridgian) and within the Kharita Formation (Albian), and shallow marine or coastal environments during deposition of the remainder of the studied succession. Paleobiogeographically, Late Jurassic index terrestrial palynomorph species documented here are in common with those previously recorded from North Africa, while marine dinocyst species are common to those documented from the West European and North American province. During the Early Cretaceous, the recorded terrestrial microfloral species were similar to those previously recorded from the West African-South American Province, while the marine dinocyst species were still related to the West European and North American marine palynofloral province.  相似文献   

16.
《China Geology》2021,4(3):476-486
The groundwater level has been continuously decreasing due to climate change and long-time overexploitation in the Xiong’an New Area, North China, which caused the enhanced mixing of groundwater in different aquifers and significant changes in regional groundwater chemistry characteristics. In this study, groundwater and sediment pore-water in drilling cores obtained from a 600 m borehole were investigated to evaluate hydrogeochemical processes in shallow and deep aquifers and paleo-environmental evolution in the past ca. 3.10 Ma. Results showed that there was no obvious change overall in chemical composition along the direction of groundwater runoff, but different hydrochemical processes occurred in shallow and deep groundwater in the vertical direction. Shallow groundwater (< 150 m) in the Xiong’an New Area was characterized by high salinity (TDS > 1000 mg/L) and high concentrations of Mn and Fe, while deep groundwater had better water quality with lower salinity. The high TDS values mostly occurred in aquifers with depth < 70 m and >500 m below land surface. Water isotopes showed that aquifer pore-water mostly originated from meteoric water under the influence of evaporation, and aquitard pore-water belonged to Paleo meteoric water. In addition, the evolution of the paleoclimate since 3.10 Ma BP was reconstructed, and four climate periods were determined by the δ18O profiles of pore-water and sporopollen records from sediments at different depths. It can be inferred that the Quaternary Pleistocene (0.78–2.58 Ma BP) was dominated by the cold and dry climate of the glacial period, with three interglacial intervals of warm and humid climate. What’s more, this study demonstrates the possibilities of the applications of pore-water on the hydrogeochemical study and further supports the finding that pore-water could retain the feature of paleo-sedimentary water.© 2021 China Geology Editorial Office.  相似文献   

17.
The current and future wind energy potentials for two square areas (SA) in the region of Freiburg were assessed and analyzed, with the aim of mitigating climate change by increasing the use of wind energy. For future conditions the regional climate models REMO and CLM were taken into account for the IPCC Emission Scenarios (SRES) A1B and B1. One aim was to provide information of the applicability of data from regional climate models in terms of wind energy. As a reference dataset, the wind energy potentials of the two measurement stations of the German Weather Service (DWD) (1961–1990) in Freiburg (SA I) and on the Feldberg (SA II) were assessed. Calculations were carried out by the Wind Analysis and Application Program (WAsP). Results were in terms of visual analysis displayed with maps. While the annual electricity performances of the reference data in SA I and SA II reach up to 7.2 GWh and 10.1 GWh respectively, the calculations for REMO and CLM show an underestimation of the real conditions for every period and Emission Scenario. Hence the applicability of the models in consideration seems to be limited. Nevertheless, with regard to different socio-economic developments (SRES A1B and B1), the results provide an overview of the wind energy potentials’ development in the different periods.  相似文献   

18.
Sporopollen, when recorded in the sedimentary record, is a characterization factor of vegetation over geological time of an area; the grain-size characteristics are direct reflection of the hydrodynamic conditions. Based on analyses of high-time resolution sporopollen and grain size of a 55-cm-long sediment core of Dongping Lake, it is shown that the sedimentary environment and hydrodynamic processes of Dongping Lake have seen significant changes over the past 150 years. From 1855 to 1865, the lake is in a hydrostatic depositional environment, where submerged plants were in great abundance, emergent and floating-leaved aquatic plants were comparatively fewer, and reworked sporopollen fossils were not observed. These indicate a weak and stable hydrodynamic condition during this stage. However, fluctuation of Mz, amounts of clay and silt were present, which may be due to high volumes of sediments around Dongping Lake basin transported into Dongping Lake via the Yellow River during the early lake-forming stages. From 1865 to 1922, the lake is in a backswamp depositional environment, where aquatic plants are nearly nonexistent, appearing occasionally in some layers with relatively low abundance. Fern spores show a twofold increase in occurrence and reworked sporopollen fossils are frequently identified. All of these indicate a strong hydrodynamic condition and frequent environmental change. Grain-size characteristics also support this interpretation. From 1922 to 1961, aquatic plants appeared at the upper layers of this zone at relatively low amounts, and reworked sporopollen fossils were frequently identified. Grain-size characteristics show an obvious change in grain-size distribution, indicating a strong hydrodynamic condition and unstable depositional environment. These relationships were attributed to a backswamp depositional environment. From 1961 to 2007, Dongping Lake is in a hydrostatic depositional environment, where the hydrodynamic condition is weak and stable. Evidence for this is shown by a remarkable increase in submerged plants, a rapid decrease in fern spores, and occasional appearances of reworked sporopollen fossils in the lower part of the zone. However, grain-size characteristics reveal that fluctuation of Mz, amounts of clay, silt and sand are noticeable and frequent, which may be mainly related to impacts of ever-enhancing human activities in recent years.  相似文献   

19.
The Songhua River plays a key role in the national development of China, owing to its unique natural condition and resources. Recent changes in the streamflow in the Songhua River are important with regard to local sustainable development and management under the background of global warming and aggravating soil erosion. In order to detect changes in the streamflow, two streamflow series from 1955 to 2004 (observed at the Harbin and Jiamusi stations) in the mainstream of Songhua River basin were obtained, and methods of statistical analysis, wavelet transform, and double mass analysis were employed to analyze the data. Reasons for the changes to the streamflow are discussed with respect to natural and man-made drivers. The results show the following: (1) From 1955 to 2004, the streamflow series present obvious declining trends. (2) The streamflow series followed the pattern of a wet–dry–wet–dry cycle pattern over the past 50 years. In the mainstream of Songhua River, wet years mainly occurred during the periods of 1955–1966 and 1984–1993, while dry years mainly occurred in the 1970s and after 2000. (3) Within the 50-year scale, the streamflow series appeared in the main periods of circa 33-, 13- and 4-year, in which the 33-year periodicity is the strongest. (4) Precipitation and temperature directly influenced the streamflow in the mainstream of the basin. The discharge was positively correlated with the precipitation and negatively correlated with the temperature. In addition, human activity was another important driving factor for streamflow change. (5) In the mainstream of Songhua River basin, the influences on streamflow can be divided into three periods: 1955–1976, 1977–1997, and 1998–2004. In the first period climate change played a dominant role, and during the latter two periods human influences were enhanced significantly.  相似文献   

20.
Latin American development is being rapidly transformed, with popularly elected governments embarking on reversals of neoliberalism informed by autochthonous notions of human wellbeing. Through a detailed examination of the origins and application of one development model, this article examines the constraints on and limits to postneoliberal development in terms of state-civil society relations and as a form of postcolonial governmentality. Interpreting Ecuadorian sumak kawsay (living well in English) in relation to embedded political cultures, specific opportunity structures, and the dynamic between contentious and electoral politics highlights the extent of room for manoeuvre in rethinking development. As a form of governmentality and pastoral power, Ecuadorian ‘postneoliberalism’ incorporates a constitutional commitment to social rights, collective citizens and the rights of nature. The paper also reveals the difficulty of making a definitive break from neoliberalism, which remains pervasive in practice, conceptualisations and state formations. Moreover, although various forms of anti-colonial ‘border thinking’ were proposed by social movement’s contentious politics, the paper argues that sumak kawsay works to sustain postcolonial conditions of development.  相似文献   

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