Los Volcanes Research Articles

Road Impact on Plant Colonization in the Arid Timanfaya National Park.

Roads have the potential to alter local environmental conditions, such as the availability of water and nutrients, and rapidly create suitable habitats for the establishment of both native and non-native plant species, transforming the ecosystems. This is a challenge in Timanfaya National Park and Los Volcanes Natural Park on Lanzarote Island, protected areas that have experienced primary succession after recent volcanic eruptions. In arid ecosystems, changes in abiotic conditions along roadsides might facilitate colonization and plant growth. We analyzed the effect of roads and road type on plant species composition and richness at a spatiotemporal scale. Vascular plant species were systematically recorded at three distances from the road edge on both sides, across fourteen zones in the wet and dry seasons, for three years. Results showed that there were slight differences on species composition depending on the distance to the road edge, as well as on the zones. Species richness was also determined by the interaction of the position, zones, and season, being higher at the road edge. Furthermore, zones with higher traffic intensity showed a higher presence of both native and non-native species. This study highlights the importance of the awareness about the road impacts on species composition by enhancing the colonization capacity of species while facilitating the entry of invasive ones. Good management practices regarding infrastructures in natural protected areas are crucial for the conservation of their unique flora, landscapes, and natural succession processes.

Changes in forest cover in Sierra Nevada, Mexico, 1994–2015

ABSTRACT Sierra Nevada, 153,437 ha, has the second and third highest mountains in Mexico and the most conserved coniferous forests of central Mexico. It comprises the Los Volcanes Biosphere Reserve, designated by UNESCO in 2010. A map was produced at 1:100,000 scale. Recent changes in forest cover were identified by visual interpretation of orthophotographs from 1994 and Spot 7 images from 2015. Changes were detected in forest cover density (closed, semi-closed, semi-open, open or deforested), together with a non-forest category that includes other land uses. Over the 21 years, 25% of the forest had undergone change: 14% recovery and 11% disturbance. Recovery outweighed disturbance in the Protected Areas, with possible factors being payment for environmental services, periodic reforestation and fire control. Outside this protected area, improvement outweighed degradation, mainly because of forestry programs. Overall in the Sierra Nevada, the trend appears to be forest recovery.

The temporal evolution of back-arc magmas from the Auca Mahuida shield volcano (Payenia Volcanic Province, Argentina)

In order to better constrain the temporal volcanic activity of the back-arc context in Payenia Volcanic Province (PVP, Argentina), we present new K–Ar dating, petrographic data, major and trace elements from 23 samples collected on the Auca Mahuida shield volcano. Our new data, coupled with published data, show that this volcano was built from about 1.8 to 1.0Ma during five volcanic phases, and that Auca Mahuida magmas were extracted from, at least, two slightly different OIB-type mantle sources with a low partial melting rate. The first one, containing more garnet, was located deeper in the mantle, while the second contains more spinel and was thus shallower. The high-MgO basalts (or primitive basalts) and the low-MgO basalts (or evolved basalts), produced from the deeper and shallower lherzolite mantle sources, respectively, are found within each volcanic phase, suggesting that both magmatic reservoirs were sampled during the 1Myr lifetime of the Auca Mahuida volcano. However, a slight increase of the proportion of low-MgO basalts, as well as of magmas sampled from the shallowest source, can be observed through time. Similar overall petrological characteristics found in the Pleistocene–Holocene basaltic rocks from Los Volcanes and Auca Mahuida volcano suggest that they originated from the same magmatic source. Consequently, it can be proposed that the thermal asthenospheric anomaly is probably still present beneath the PVP. Finally, our data further support the hypothesis that the injection of hot asthenosphere with an OIB mantle source signature, which was triggered by the steepening of the Nazca subducting plate, induced the production of a large volume of lavas within the PVP since 2Ma.

Cosmogenic 3He and 21Ne surface exposure dating of young basalts from Southern Mendoza, Argentina

Southern Mendoza, Argentina, is characterised by abundant Pleistocene to Holocene volcanism associated with back-arc magmatism, influenced by the subducting Nazca plate. Age determinations in this volcanic area have been improved during the last 5 years. However, there are some volcanic features especially in the Payunia Volcanic Field (PVF) which suggest fairly recent eruptions and which have not been chronologically determined. Recent studies on the Llancanelo Volcanic Field (LLVF) and PVF have determined volcanic activity mainly using K–Ar and 40Ar/39Ar as well as cosmogenic 3He. However, K–Ar and 40Ar/39Ar fail to produce reliable ages in Holocene basaltic flows. To better constrain the younger volcanic activity in the LLVF and especially in the PVF, surface exposure dating using cosmogenic 3He and 21Ne was applied to five volcanic features. By applying this method, 3He and 21Ne ages ranging from late Pleistocene to mid Holocene were obtained for basalts from the area of Los Volcanes, from the PVF. The youngest age acquired is significant as it supports previous evidence for mid Holocene volcanic activity in the PVF and constitutes the first noble gas cosmogenic surface exposure age obtained from a basaltic bomb. This paper illustrates the advantages of using two nuclides (3He and 21Ne) for cosmic-ray exposure ages in the study of recent volcanic eruptions. The results in the present study indicate that the PVF was active in the last 5 ka.

Cosmogenic 3He exposure ages of basalt flows in the northwestern Payún Matru volcanic field, Mendoza Province, Argentina

The Payún Matru volcanic field encompasses more than 12,000 km2 in the west-central Argentine province of Mendoza. The northwestern part of the field, called Los Volcanes, includes multiple basaltic lava flows and numerous cinder cones and scoria fields. We sampled primary lava flow features (tumuli, pahoehoe and aa flow surfaces) from two different basaltic lava flows and one fluvial strath for cosmogenic 3He exposure age dating in the Los Volcanes area. Olivines from the sampled basalts have low concentrations of U and Th and a minimal radiogenic 4He correction. We used the recently established R correction factor to correct our measured 3He concentrations for magmatic 3He and 4He and radiogenic 4He. Exposure ages for primary lava flow features covering a large area just east of where Route 40 crosses the Río Grande range from 41 to 43 ka with external uncertainties on the order of 7%. A recently published K→Ar age of 26 ± 5 ka was sampled within a few hundred meters of three of our cosmogenic exposure age samples and appears to be from the same basalt flow. Given the large uncertainties associated with dating young lava flows, the K→Ar age and our cosmogenic ages are in reasonable agreement; however, they do not overlap within uncertainties and suggest possible systematic discrepancies between the two methods of up to 20% in this instance. A sample from a bedrock strath carved by the Río Grande into basalt yielded a surface exposure age of 17 ± 1 ka. The toe of a much younger-looking aa flow about 5 km west of the Rt. 40 Río Grande bridge yielded two ages of 0 and 2 ka, and is presumed to be historical.

Deformation and Gravity Change: Indicators of Isostasy, Tectonics, Volcanism and Climate Change, Volume III. Introduction

The workshop on Deformation and Gravity Change: Indicators of Isostasy, Tectonics, Volcanism and Climate Change took place at the Casa de los Volcanes on Lanzarote, Spain, during March 1–4, 2005 (see Fig. 1). It was jointly organized and supported by the International Association of Geodesy (IAG), the Spanish Ministry of Education and Science, the Spanish Council for Scientific Research and the Cabildo Insular de Lanzarote. From an organizational point of view, the workshop also served as the first meeting of the members the IAG Working Group ICCT2 on Dynamic Theories of Deformation and Gravity Fields existing since late 2003, but was open to all “external” colleagues interested in its topic.

Volcanic evolution of the back-arc Pleistocene Payun Matru volcanic field (Argentina)

Abstract For the first time, about 30 volcanic formations of the back-arc Payun Matru volcanic field (Payun Matru volcanic field, Argentina, 36°S, 69°W) have been sampled for K–Ar geochronology and geochemistry in order to reconstruct the eruptive history of this key province in the Andean back-arc. The Payun Matru volcanic field has been built since final Pleistocene until present with ages ranging from 280 ± 5 to 7 ± 1 ka. Erupted lavas belong to calc-alkaline series, with characteristics of both arc and intraplate magmas. From previous studies, three main units are distinguished: (1) a basaltic field (Los Volcanes), which covers a large surface of the Payun Matru volcanic field, composed of strombolian cones and associated lava flows emitted from 300 ka to Holocene times, (2) the stratovolcano Payun, with intermediate compositions, built around 265 ka, and (3) the shield volcano Payun Matru s.s. characterized by trachytic compositions and a large summit caldera. The earlier stages of the Payun Matru volcano are not dated, but we constrain the major explosive event, related to the eruption of a widespread ignimbrite and to the formation of the caldera, between 168 ± 4 ka (internal wall of caldera) and 82 ± 1 ka (flow within the caldera). Based on the geochemical similarities of the ignimbrite and the upper lava flow of the pre-caldera cone, we suggest that the age of this event is most probably at the older end of this interval. Numerical modeling using a GIS program has been used to reconstruct the morphological evolution for Payun Matru volcano before and after the caldera collapse. The ancient edifice could be modeled as a flattened cone, 2300 m high, with a volume of about 240 km3. The ignimbrite eruption associated with the Payun Matru caldera formation could be related to the regional tectonic environment, which is characterized by multiple Plio-Pleistocene extensional stages during the last 5 Myr. The evolution of the Nazca plate subduction from a flat slab to a normal dip induced an input of fluid mobile elements and asthenosphere plume-like mantle source beneath the Patagonian lithosphere, which yields the observed intraplate signature. We also interpret this geodynamic evolution as the influence of extensive processes in the upper crust leading to caldera-forming eruptions as observed throughout this province.

Classification, natural history, and evolution of Epiphloeinae (Coleoptera: Cleridae). Part VII. The genera Hapsidopteris Opitz, Iontoclerus Opitz, Katamyurus Opitz, Megatrachys Opitz, Opitzia Nemesio, Pennasolis Opitz, new genus, Pericales Opitz, new genus, Pteroferus Opitz, new genus, and Turbophloeus Opitz, new genus

This study deals with minimally speciose epiphloeine genera. Hapsidopteris, based on H. diastenus Opitz, (type locality: México: Jalapa), is the presumed sister taxon of Opitzia Nemésio [type species: O. chiapas (Opitz), type locality: México: Chiapas: 39 km NW Comitán] a bitypic genus that also includes O. apicula, new species (type locality: Bolivia: Santa Cruz: Amboro Road, above Achira Campo). Two species define Iontoclerus Opitz, I. humeralis (Klug) (type locality: Brazil: Parà) and I. sericeus (Klug) (type locality: Brazil: Rondonia: 62 km SE Ariquemes), whose presumed sister genus is the monotypic Pericales, new genus, based on P. albogilvus, new species (type locality: Haiti: Sud-Ouest: Massif de La Selle, Morne d’Enfer). The Middle American bitypic Katamyurus Opitz [type species: K. paxillus Opitz, type locality: Nicaragua: Cerro Chimborazo], which also includes K. albopaniculus, new species (type locality: México: Sinaloa: 14 km NE La Cap. del Taxte), is considered the sister taxon to Ellipotoma Spinola (type species: E. tenuiformis Spinola. Type locality: Colombia). Megatrachys Opitz (type species: Megatrachys paniculus Opitz (type locality: México: Chiapas: 8 km W San Cristóbal) contains two additional species, M. bibara, new species (type locality: Guatemala: Zacapa: 2 km San Lorenzo) and M. truncatia, new species (type locality: México: Chiapas: 47.5 km NW Comitán) and is the hypothesized sister taxon to Pennasolis, new genus [type species; P. merkeli (Horn), type locality: Arizona: Cochise County, South West Research Station, 8 km W Portal], which in addition to the type species also contains P. californica (Van Dyke) (type locality: California: Yosemite National Park, Yosemite Valley. The phylogenetic relationships of two South American monotypic genera have not been deciphered; these are Pteroferus, new genus, based on P. zolnerowichi, new species (type locality: Brazil: Santa Catarina: Nova Teutonia), and Turbophloeus, new genus, based on T. simplex (Schenkling) whose type locality is Bolivia: Santa Cruz: Amboro National Park, Los Volcanes. Lectotypes are designated for Pennasolis merkeli (Horn), Iontoclerus humeralis (Klug), I. sericeus (Klug), and Turbophloeus simplex (Schenkling). The latter binomial represents a new combination whose specific epithet was originally associated with Epiphloeus.

The San Nicolás Formation: A Proto-Gulf Extensional-Related New Lithostratigraphic Unit at Bahía San Nicolás, Baja California Sur, Mexico

A detailed study and mapping of the Neogene volcanosedimentary rocks cropping at the Bahía San Nicolás, Baja California Sur, was carried out, allowing reconnaissance and formal description of the San Nicolás Formation (a lithostratigraphic unit constituted from older to younger by the lower Toba San Antonio, Los Volcanes, Arroyo Amarillo, and the upper El Saucito members). These units reflect syn-to-postextensional episodes associated to the Gulf of California Province that show initial high subsidence onto dry land associated with low rates of sedimentation followed by shallow marine water deposition dominated by storm and macro tidal processes. The maximum age assigned to the units is 3.3 ± 0.5 Ma.

Alkaline Lavas in the Volcanic Front of the Western Mexican Volcanic Belt: Geology and Petrology of the Ayutla and Tapalpa Volcanic Fields

The Plio-Quaternary Ayutla and Tapalpa volcanic fields in the INTRODUCTION volcanic front of the western Mexican Volcanic Belt (WMVB) In a widely accepted model of subduction zones, fluidcontain a wide variety of alkaline volcanic rocks, rather than only fluxed mantle peridotite begins to melt at a depth of calc-alkaline rocks as found in many continental arcs. There are >100 km, and some of this melt rises to form the volcanic three principal rock series in this region: an intraplate alkaline series front of the arc (e.g. Davies & Stevenson, 1992; Arculus, (alkali basalts and hawaiites), a potassic series (lamprophyres and 1994). As a result, magma erupted at the volcanic front trachylavas), and a calc-alkaline series. Phlogopite-clinopyroxenite can provide information about conditions in the sub-arc and hornblende-gabbro cumulate xenoliths from an augite minette mantle and the nature of the fluids and melts being lava flow have orthocumulate textures. The phlogopite-clinopyroxenite released and generated there. The great diversity of mafic xenoliths also contain apatite and titanomagnetite and probably volcanic rocks produced in the western Mexican Volcanic formed by accumulation of minerals fractionated from an augite Belt (WMVB) (e.g. Allan et al., 1991) is due in part to minette more primitive than the host. The intraplate alkaline series different amounts and types of fluids fluxing the mantle is probably generated by decompression melting of asthenospheric wedge. However, the majority of the diverse basic mantle as a result of corner flow in the mantle wedge beneath the magmas have erupted within tectonic depressions, makarc. Alkaline magmas may be common in the WMVB as a result ing it unclear whether the unusually diverse compositions of prior metasomatism (during Tertiary Sierra Madre Occidental are an intrinsic characteristic of the subduction magmagmatism) of the Mexican sub-arc mantle. Generation of the more matism or have been amplified by extension. Lavas from evolved andesites and dacites of the calc-alkaline series is due to the volcanic front of the WMVB have been studied in either combined assimilation and fractional crystallization (AFC) the Tepic, San Sebastian, Los Volcanes, and Mascota or magma mixing. The preponderance of alkaline and hydrous lavas regions in the north (Nixon et al., 1987; Verma & Nelson, in this region demonstrates that these lava types are the norm, rather 1989; Righter et al., 1995; Carmichael et al., 1996) and than the exception in western Mexico, and occur in regions that are also in the Sayula and Colima regions in the south (Luhr not necessarily associated with active rifting. & Carmichael, 1981; Allan & Carmichael, 1984).

Reacciones adversas y problemas relacionados con medicamentos en un servicio de urgencia

FUNDAMENTO: Las Reacciones Adversas a Medicamentos y los Problemas Relacionados con Medicamentos (PRM), son una causa frecuente de asistencia en los servicios de urgencias y requieren una mejor evaluación. MÉTODO: Se analizaron 1.097 admisiones consecutivas en el servicio de urgencias de "Nuestra Señora de los Volcanes" (actualmente "Hospital General de Lanzarote") en Arrecife de Lanzarote (Islas Canarias) durante un período de tres meses, para determinar la existencia de Reacciones Adversas a Medicamentos o de otros problemas relacionados con fármacos. RESULTADOS: Diecinueve de las 1.097 admisiones se debieron a reacciones adversas a medicamentos (1.73%; 95 % CI: 0.96 % - 2.5%). Entre los otros "Problemas Relacionados con los Medicamentos", destacaron la intoxicación por medicamentos, que se diagnosticó en 5 de los pacientes (0.45%); el agravamiento del cuadro clínico por supresión del medicamento apareció en 8 (0.72%) y los tratamientos inadecuados que precisaron atención médica en el servicio de urgencia fueron 11 (1.0%). El número total de problemas relacionados con medicamentos en la muestra fue de 43 (3.9%). Los problemas relacionados con medicamentos causaron hospitalización en el 1.9% de los pacientes atendidos en urgencias y resultó ser la causa de hospitalización en el 9.6% del total de ingresos urgentes en el hospital durante el periodo de estudio. En cuanto a las reacciones adversas a medicamentos causaron 4.1% del total de ingresos en el hospital. CONCLUSIONES: Los problemas relacionados con los medicamentos son un problema frecuente, importante y no bien estudiado en los servicios de urgencias. Además, los servicios de urgencias pueden actuar como el primer sitio de reconocimiento para las reacciones adversas a medicamentos en la población ambulatoria.

Alkaline and calc-alkaline lavas near Los Volcanes, Jalisco, Mexico: geochemical diversity and its significance in volcanic arcs

A remarkably diverse suite of lavas erupted during the late-Pliocene at the volcanic front of the western Mexican Volcanic Belt near the town of Los Volcanes, Jalisco. This region is much closer to the Middle America Trench than the main axis of Quaternary andesite-dacite stratovolcanoes, and volcanism occurred in a complex tectonic regime involving both subduction of the young Rivera Plate and transverse crustal extension of the Jalisco structural block. The variety of lava types covers a wide spectrum from highly potassic minettes and leucitites to calc-alkaline basalts and andesites which are compositionally similar to those erupted elsewhere in the Mexican Volcanic Belt. Other alkaline varieties intermediate between these extremes include absarokites, trachybasalts and trachyandesites. Phlogopite, amphibole and apatite are common phenocryst phases; whole-rock compositions show a wide range of alkali contents (e.g. K2O of 1.0–8.6 wt.%), and typically contain >5 wt.% MgO. MgO, Ni, V and Cr show little systematic decrease with increasing SiO2, suggesting that these lavas have evolved from primitive, mantle derived magmas with a wide range of SiO2 contents. Strong enrichments in incompatible trace elements are observed in all of the lavas (Sr 700–5100 ppm, Ba 470–4800, Ce 22–325 ppm, Zr 90–700 ppm), as is the relative enrichment of large ion lithophile (Ba, Sr, Rb) and light rare-earth elements (La, Ce) over the high field strength elements (Ti, Zr) which is typical of magmas in volcanic arcs. This enrichment pattern suggests that these magmas come from source regions which contain incompatible element-rich phases such as phlogopite, amphibole and apatite. The petrological and geochemical features of the lavas which occur in the Los Volcanes region provide direct evidence of the extreme heterogeneity which may exist in magma source regions at convergent margins. The complex tectonic regime in western Mexico further suggests that rifting and crustal extension play an important role in the generation and successful ascent of melts from enriched regions of the sub-arc mantle.

Minette lavas and associated leucitites from the western front of the Mexican Volcanic Belt: petrology, chemistry, and origin

During the late Pliocene, K-rich minette and leucitite lavas erupted in the western Mexican Volcanic Belt near the town of Los Volcanes, a region which is located much closer to the Middle America Trench than the main line of currently active andesite stratovolcanoes. During this period the tectonic regime in western Mexico was highly complex due to the simultaneous occurrence of active subduction of the young Rivera Plate, and rifting caused by crustal extension. Most of these basic lavas contain phenocrysts of phlogopite, augite and apatite, along with microphenocrysts of leucite and Fe-Ti oxide. Olivine is absent from all but two of the flows: one an olivine leucitite, and the other a felsic minette. The phlogopite phenocrysts and high whole rock Fe2O3/FeO ratios which are characteristic of this suite record evidence of high magmatic water contents and oxygen fugacities. All of these rock types are highly enriched in the large ion lithophile and light rare earth elements, with Sr≤5100 ppm, Ba≤4800 ppm and Ce≤330 ppm. They are also mildly enriched in the high field strength elements (e.g. Zr 260–700 ppm) and display the strong relative enrichment of the LILE over the HFSE that is characteristic of magmas erupted in convergent margins. Consideration of high pressure phase equilibria in the Mg2SiO4-CaMgSi2O6-KAlSiO4-SiO2 system shows that the minettes from this region are not related through fractional crystallization to the more MgO-rich, olivinebearing minettes which have erupted in other parts of the western Mexican Volcanic Belt during the Quaternary. This conclusion is consistent with both the trace element geochemistry of these lavas and with the results of fractional crystallization models. Instead, the data suggests that these high-K magmas were derived from a source region which consists predominantly of phlogopite, clinopyroxene and apatite, and which has formed through hydrous enrichment of the subarc mantle in response to subduction.