Thermal structure, coupling and metamorphism in the Mexican subduction zone beneath Guerrero   总被引：2，自引：0，他引：2  

V. C. Manea  M. Manea  V. Kostoglodov  C. A. Currie  G. Sewell 《Geophysical Journal International》2004,158(2):775-784

  相似文献   

汛期西南低涡移向频数的年际变化与降水   总被引：4，自引：0，他引：4  

段炼 《气象》2006,32(2):23-27

利用1960～1999年汛期西南低涡不同移向的数据资料与同期移向相对应站点的降水量进行同步相关分析和检验，并将通过显著水平a=0．05检验的两组资料用墨西哥帽子波进行分析。结果显示：这40年汛期中出现的西南低涡，在原地生消的占总数的一半以上，而能够继续移动发展的西南低涡以偏东路径为主；东北路径的西南低涡与该方向上太原、石家庄降水的相关比较好，偏东路径与汉口降水相关较好，移动总和与内江降水相关较好；从小波分析结果发现东北、偏东路径低涡出现次数与对应站点降水，在10年以上的时间尺度上它们的分布周期存在良好的对应关系。  相似文献   

Maquiladora Myths: Locational and Structural Change in Mexico's Export Manufacturing Industry     

Ian MacLachlan  Adrian Guillermo Aguilar 《The Professional geographer》1998,50(3):315-331

Trends in location, labor force, and procurement practices in maquiladoras are examined using recent data sources. A growing proportion of maquiladoras are selecting interior locations, south of the borderlands. Once dominated by young women, the labor force is rapidly approaching gender parity. While far below prevailing rates in the United States, maquiladora wages are comparable with equivalent manufacturing sectors in Mexico. Majority ownership of maquiladoras is split almost evenly between Mexico and the U.S., however, maquiladoras have failed to develop domestic sources of materials and parts and remain dependent on imported material inputs. As the North American Free Trade Agreement is phased in, the regulatory environment of maquiladoras will change but their role as low cost assembly specialists will persist.  相似文献   

Low calcification rates and calcium carbonate production in Porites panamensis at its northernmost geographic distribution          下载免费PDF全文

Carlos Orión Norzagaray‐López  Luis Eduardo Calderon‐Aguilera  José Martín Hernández‐Ayón  Héctor Reyes‐Bonilla  Juan P. Carricart‐Ganivet  Rafael Andrés Cabral‐Tena  Eduardo Francisco Balart 《Marine Ecology》2015,36(4):1244-1255

Porites panamensis is a hermatypic coral present in the eastern Pacific Ocean. Skeletal growth parameters have been reported, but studies of the relationship between annual calcification rates and environmental controls are scarce. In this study, we investigated three aspects of the annual calcification rates of P. panamensis: growth parameters among three P. panamensis populations; the sea surface temperature as a calcification rate control spanning a latitudinal gradient; and calcium carbonate production among three sites. Growth parameters varied among the sites due to the colony growth form. Massive colonies in the north showed a higher calcification rate than encrusting colonies in the south (mean: 1.22–0.49 g CaCO₃ · cm^?2 · yr^?1), where variations in calcification rates were related to growth rate (0.91–0.38 cm · yr^?1) rather than to skeletal density differences (overall mean ± SD, 1.31 ± 0.04 g CaCO₃ · cm^?3). Our results showed a positive linear relationship between annual calcification rates and sea surface temperatures within these P. panamensis populations. Differences were related to distinct oceanographic environments (within and at the entrance of the Gulf of California) with different sea surface temperature regimes and other chemical properties. Different populations calcified under different environmental conditions. Calcium carbonate production was dependent upon the calcification rate and coral cover and so carbonate production was higher in the north (coral cover 12%) than in the south (coral cover 3.5). Thus, the studied sites showed low calcium carbonate production (0.25–0.43 kg CaCO₃ · m^?2 · yr^?1). Our results showed reduced calcification rates, regional temperature regime control over calcification rates, different growth forms, low coral cover and low calcium carbonate production rates in P. panamensis.  相似文献   

From adoption to implementation? An academic perspective on Sustainable Fisheries Management in a developing country     

《Marine Policy》2015

Despite the fact that Sustainable Fisheries Management (SFM) has long been proposed internationally, it remains controversial. Practical and successful applications are scarce, especially in developing countries with a recent history of massive overfishing, such as Mexico. Although SFM has been adopted at the highest level of the Mexican legal framework during the last two decades, its successful implementation still faces a series of complex challenges. At present, important changes in the Mexican political regime are at a breaking point, motivating the academic discussion about the national implications of adopting SFM approaches. Through the analysis of a series of deep interviews of key actors, combined with published material, the article illustrates how the fast-track adoption of SFM approaches has fared in a national fisheries context, the current situation being largely dysfunctional with regard to the challenges of SFM. A complicated mixture between unbeaten management and academic vestiges caused the present circumstances of an enhanced but limited fisheries system. The article proposes academic initiatives required to improve the implementation of SFM in Mexico based on an enhanced understanding of domestic historic conditions and challenges.  相似文献   

Evolution of a complex isolated dome system,Cerro Pizarro,central México     

Nancy?RiggsEmail author  Gerardo?Carrasco-Nunez 《Bulletin of Volcanology》2004,66(4):322-335

Cerro Pizarro is an isolated rhyolitic dome in the intermontane Serdán-Oriental basin, located in the eastern Trans-Mexican Volcanic Belt. Cerro Pizarro erupted ~1.1 km³ of magma at about 220 ka. Activity of Cerro Pizarro started with vent-clearing explosions at some depth; the resultant deposits contain clasts of local basement rocks, including Cretaceous limestone, ~0.46-Ma welded tuff, and basaltic lava. Subsequent explosive eruptions during earliest dome growth produced an alternating sequence of surge and fallout layers from an inferred small dome. As the dome grew both vertically and laterally, it developed an external glassy carapace due to rapid chilling. Instability of the dome during emplacement caused the partial gravitational collapse of its flanks producing various block-and-ash-flow deposits. After a brief period of repose, re-injection of magma caused formation of a cryptodome with pronounced deformation of the vitrophyric dome and the underlying units to orientations as steep as near vertical. This stage began apparently as a gas-poor eruption and no explosive phases accompanied the emplacement of the cryptodome. Soon after emplacement of the cryptodome, however, the western flank of the edifice catastrophically collapsed, causing a debris avalanche. A hiatus in eruptive activity was marked by erosion of the cone and emplacement of ignimbrite derived from a caldera to the north of Cerro Pizarro. The final growth of the dome growth produced its present shape; this growth was accompanied by multiple eruptions producing surge and fallout deposits that mantle the topography around Cerro Pizarro. The evolution of the Cerro Pizarro dome holds aspects in common with classic dome models and with larger stratovolcano systems. We suggest that models that predict a simple evolution for domes fail to account for possibilities in evolutionary paths. Specifically, the formation of a cryptodome in the early stages of dome formation may be far more common than generally recognized. Likewise, sector collapse of a dome, although apparently rare, is a potential hazard that must be recognized and for which planning must be done.Editorial responsibility: J. Gilbert  相似文献   

Dynamics of coastline changes in Mexico     

Valderrama-Landeros  Luis H.  Martell-Dubois  Raúl  Ressl  Rainer  Silva-Casarín  Rodolfo  Cruz-Ramírez  Cesia J.  Muñoz-Pérez  Juan J. 《地理学报(英文版)》2019,29(10):1637-1654

Journal of Geographical Sciences - The goal of our work was to locate and quantify changes that occurred in 66% of the Mexican coastline, based on four land cover maps generated by the Mexican...  相似文献   

Spatio‐temporal variation in density and size structure of the endangered sea cucumber Isostichopus fuscus in Huatulco National Park,Mexico          下载免费PDF全文

Andrea Glockner‐Fagetti  Francisco Benítez‐Villalobos 《Marine Ecology》2017,38(1)

The brown sea cucumber Isostichopus fuscus (Ludwig, 1875) has been subjected to strong fishing pressure and is currently considered an endangered species by the IUCN Red List of Threatened Species. Spatial and temporal variations in density were analysed and population parameters of I. fuscus were estimated in three localities of the Southern Mexican Pacific. Density was estimated using circular transects covering a 300 m² area in each locality. Body length and weight were also measured. The mean density was 0.018 ± 0.013 individuals·m^?2, and was statistically significantly lower during summer. The mean length and weight were 22.4 ± 3.8 cm and 396 ± 130 g, respectively, and statistically significant differences were found among localities. The weight–length relationship was W = 0.28·L^1.32 and the mean relative condition index (Kn) = 1.04 ± 0.31. The von Bertalanffy growth equation was L_t = 38.7·(1–exp^(?0.4·t)). The lowest values of length, weight and age were found at Dos Hermanas, suggesting that this locality could be favorable for the settlement of larvae and recruitment and growth of juveniles. The present study is the second to estimate densities of I. fuscus and the first one to publish data on size structure and growth for the population at Bahias de Huatulco. The densities were so low in the three sampled localities that none of them would be able to support a fishery, even under a sustainable management scheme. The information collected in the present study could be helpful for management programs of the Huatulco National Park, as all the data used for these currently come mainly from the populations of I. fuscus in the Gulf of California.  相似文献   

墨西哥西马德雷山脉中—新生代构造、岩浆演化及成矿特征   总被引：1，自引：0，他引：1  

姚春彦  姚仲友  李汉武  郭维民  刘君安 《地质通报》2017,36(12):2124-2133

墨西哥西马德雷山脉是白垩纪—新生代岩浆活动和构造运动形成的。中新生代岩浆活动可以分为5个主要阶段:侏罗纪—早白垩世、晚白垩世—古新世、始新世—渐新世、中新世早期和中新世中期—现代。这些岩浆活动和构造运动与法拉隆(Farallon)板块向北美大陆俯冲和加利福尼亚湾打开相关。墨西哥中新生代的成矿作用与东太平洋板块边缘连续的俯冲过程密切相关,矿床类型多样,包括VMS(与火山相关的块状硫化物)型、斑岩型、IOCG(铁氧化物铜金)型、矽卡岩型等。  相似文献   

RESURGENT MEXICAN PHOENIX*   总被引：1，自引：0，他引：1  

Alex P. Oberle  Daniel D. Arreola 《Geographical review》2008,98(2):171-196

ABSTRACT. Popular impressions of Phoenix, Arizona perpetuate the notion that this metropolitan area is an overwhelmingly Anglo place. We challenge this assertion and demonstrate that the city has substantial Mexican roots and is presently being shaped by a vibrant, resurgent Mexican population. Employing historical records, surveys, and landscape data, we articulate the Mexican character of early Phoenix and highlight how the revival of Mexican Phoenix has transformed the urban landscape. We then relate how Phoenix's Mexican population is a more nuanced regional subculture formed through both historical and contemporary connections with specific Mexican states. We conclude with a call for greater understanding of the internal heterogeneity of Mexicans in the United States and how this can inform our geographical interpretations of the growing Latinization of American cities.  相似文献