Search

Volcanic eruptions of the directed blast type are characterized by powerful explosions with a significant lateral pyroclastic density current (PDC) component that can travel at speeds above 100 m s–1 and affect hundreds of square kilometers around a volcano. This study presents preliminary results of a detailed fieldwork and stratigraphic study of deposits associated with the Ocoxaltepec Blast deposit, which originated from the Popocatépetl volcano during a strong eruption associated with the southwestward sector collapse of the volcanic edifice around 23,500 ka BP. Within the study area, which contains 58,870 inhabitants, we found 42 new sites where the blast deposit outcrops, in locations up to 25 km from the volcano crater, with thicknesses up to over 20 m. We divide these blast deposits into two categories: confined channel-fill PDC deposits and unconfined interfluve and upland PDC deposits. With the new data we have estimated the dispersion area of the directed blast to be approximately 338 km2. Twenty-nine of the new outcrops are located outside the hazard polygon associated with concentrated PDCs related to the lowest probability Plinian eruption currently considered from Popocatépetl.

Transitions from effusive to explosive activity can increase hazards making it crucial to define early indicators such as changes in the magnetic signals. After more than 80 cycles of crater-dome extrusion and destruction from 1996 on, Popocatépetl volcano (Mexico) experienced changes in its behavior from March 15 to 18 July 2019, when no lava domes were observed. Some of the domes behaved as contained lava flows within the crater floor (pancakes) while others were more irregular-shaped. Activity decreased considerably over this 2019 interval except for the unexpected explosions in March and June, that produced ash plumes reaching up to 14,000 m a.s.l. In order to investigate the causes of the transition from effusive to explosive behavior in March and June, we analyzed the time series from the magnetic monitoring network at Popocatépetl volcano between October 2018 and December 2019. The raw signals were analyzed by weighted differences (WD) based on the elimination of non-local changes from the total intensity values of the geomagnetic field and the discrete-time continuous wavelet transform was used to evaluate the local variations of energy within the time series. The high energy periods (linked to negative magnetic anomalies) are induced by magma ascent associated with movement within the conduit. They indicate that the sudden explosions were due to the ascent of several magma batches that were slowed during ascent and were not able to reach the surface. Changes in the rheology of the lava are linked to the influx of several batches of magma with different compositions as well as to compaction by gas loss when ascending andesitic magma pushed out overlying more viscous degassed magma clearing the conduit, which can explain why these sudden explosions were more energetic. Several geophysical data sets as well as tephra compositions were integrated to support this conclusion. The correlated multiparameters also confirm that geomagnetic volcano monitoring has been essential in understanding the processes that drive the observed changes in eruptive behavior. We present new evidence for the detection of transient events produced by magma ascent and changes in the feeding system of Popocatépetl volcano with wavelet analysis. Detailed vulcanomagnetic processing, especially when it is correlated with other monitoring parameters, provides information on ascending magma and several Frontiers in Earth Science 01 frontiersin.org Martin-Del-Pozzo and Santos Morales 10.3389/feart.2024.1204859 conduit processes that would otherwise be camouflaged. Ascending batches may precede an eruption but they can also ascend in several pulses indicating how dome growth occurs. [ABSTRACT FROM AUTHOR]

Transitions from effusive to explosive activity can increase hazards making it crucial to define early indicators such as changes in the magnetic signals. After more than 80 cycles of crater-dome extrusion and destruction from 1996 on, Popocatépetl volcano (Mexico) experienced changes in its behavior from March 15 to 18 July 2019, when no lava domes were observed. Some of the domes behaved as contained lava flows within the crater floor (pancakes) while others were more irregular-shaped. Activity decreased considerably over this 2019 interval except for the unexpected explosions in March and June, that produced ash plumes reaching up to 14,000 m a.s.l. In order to investigate the causes of the transition from effusive to explosive behavior in March and June, we analyzed the time series from the magnetic monitoring network at Popocatépetl volcano between October 2018 and December 2019. The raw signals were analyzed by weighted differences (WD) based on the elimination of non-local changes from the total intensity values of the geomagnetic field and the discrete-time continuous wavelet transform was used to evaluate the local variations of energy within the time series. The high energy periods (linked to negative magnetic anomalies) are induced by magma ascent associated with movement within the conduit. They indicate that the sudden explosions were due to the ascent of several magma batches that were slowed during ascent and were not able to reach the surface. Changes in the rheology of the lava are linked to the influx of several batches of magma with different compositions as well as to compaction by gas loss when ascending andesitic magma pushed out overlying more viscous degassed magma clearing the conduit, which can explain why these sudden explosions were more energetic. Several geophysical data sets as well as tephra compositions were integrated to support this conclusion. The correlated multiparameters also confirm that geomagnetic volcano monitoring has been essential in understanding the processes that drive the observed changes in eruptive behavior. We present new evidence for the detection of transient events produced by magma ascent and changes in the feeding system of Popocatépetl volcano with wavelet analysis. Detailed vulcanomagnetic processing, especially when it is correlated with other monitoring parameters, provides information on ascending magma and several conduit processes that would otherwise be camouflaged. Ascending batches may precede an eruption but they can also ascend in several pulses indicating how dome growth occurs.

The inhalation of natural nanoparticles (NPs) emitted from volcanic activity may be a risk to human health. However, the literature rarely reports the fate and response of NPs once in contact with lung fluids. In this work, we studied the particle size distribution of ashfall from Popocatépetl volcano, Mexico. The collected ashes (n = 5) were analyzed with scanning electron microscopy (SEM) to obtain the elemental composition and morphology, and to determine the size of the ash particles using ParticleMetric software (PMS). The PMS reported most of the ash to have submicrometric size (<1 μm) and an average equivalent circle of 2.72 μm. Moreover, to our knowledge, this study investigated for the first time the behavior of ash NPs at different times (0 to 24 h) while in contact with in vitro lung fluid, Gamble Solution (GS) and Artificial Lysosomal Fluid (ALF) using dynamic light scattering (DLS). We found a large variability in the hydrodynamic diameter, with values less than 1 nm and greater than 5 μm. Furthermore, aggregation and disaggregation processes were recognized in GS and ALF, respectively. The results of this study increase the knowledge of the interaction between NPs and lung fluids, particularly within the alveolar macrophage region. [ABSTRACT FROM AUTHOR]

Volcanic CO2 emissions inventories have great importance in the understanding of the geological carbon cycle. Volcanoes provide the primary pathway for solid-earth volatiles to reach the Earth’s atmosphere and have the potential to significantly contribute to the carbon-climate feedback. Volcanic carbon emissions (both passive and eruptive degassing) included in inventories, largely stem from patchy surface measurements that suffer from difficulties in removing the atmospheric background. With a 27-year-long ongoing open-vent eruption, Popocatépetl ranks as one of the highest permanent volcanic CO2 emitters worldwide and provides an excellent natural laboratory to design and experiment with new remote sensing methods for volcanic gas emission measurements. Since October 2012, infrared spectra at different spectral regions have been recorded with a solar occultation FTIR spectrometer. The near-infrared spectra allow for high precision measurements of CO2 and HCl columns. Under favorable conditions, the continuous observations during sunrise allow the reconstruction of a plume cross-section of HCl and the estimation of the emission flux using wind data. Despite that the detection of CO2 is more challenging, on April 26th, 2015 we captured a volcanic plume under favourable wind conditions which allowed us to reconstruct from this particular event a CO2 emission rate of 116.10 ± 17.2 kg/s. The volcanic HCl emission on this event was the highest detected during the 2012-2016 period. An annual average CO2 emission estimate of (41.2 ± 16.7) kg/s ((1.30 ± 0.53) Tg/yr) could be determined from a statistical treatment of the detected CO2 and HCl columns in the IR spectra, and their corresponding molecular ratios, during this period. A total of 25 events were used to derive a mean CO2/HCl molecule ratio of 11.4 ± 4.4 and an average HCl emission rate of (3.0 ± 0.3) kg/s could be determined. The CO2 emissions of Popocatépetl were found to be around 0.32% of the total anthropogenic CO2 emissions reported in the country and 3.6% of those corresponding to the Mexico City Metropolitan Area (MCMA). CO2 emissions from the Popocatépetl volcano can be considered to play a negligible role in the global CO2 budget, but should be taken into account.

We describe three unique types of seismicity at Popocatépetl volcano that accompanied the initial vent-clearing eruptive activity in December 1994 through the eruption of the first two domes in 1996. We identify and describe two types of coupled events, 1) spasmodic burst coupled events, a burst of volcano tectonic (VT) events coupled with a large eruptive explosion (21 December 1994 and 5 March 1996), and 2) explosion-couplet coupled events, a pair of events with a deeper first event and whose second event correlates with a small gas emission or explosion. Explosion-couplets occurred with the onset of magmatic ash dominated eruptions and their properties are very useful for forecasting magmatic eruptions at Popocatépetl volcano. Measurable quantities including the time between the first and second phase, daily numbers of events, and the amplitude ratio between the second and first phase systematically changed as the first two domes approached the surface between March and June 1996. Interevent times decreased from many tens of seconds to a few seconds, while amplitude ratios increased from about 2 to 10 or more. Event numbers increased prior to and during initial dome extrusion. These changes were used to forecast the eruption of the first two domes. We also report on another unusual type of low frequency seismicity that accompanied emissions called fluidized bed events. Fluidized bed events occurred following the initial eruption on 21 December 1994, beginning mid-January 1995, when SO 2 emissions were initially elevated, and the conduit was open. Fluidized bed events began to wane in late March through the end of May 1995 as did SO 2 emissions. Consistent gas, visual and seismic observations by Centro Nacional de Prevención de Desastres (CENAPRED) enabled the direct correlation of the gas, magma, and seismic phenomena. • A spasmodic burst coupled event comprised the first eruption in December 1994. • Fluidized bed events dominated for several months following the first eruption. • A pair of coupled events comprised the second eruption in March 1996. • Explosion-couplet interevent times decreased prior to dome extrusions in 1996. • Amplitude ratios of explosion-couplets increased prior to dome extrusions in 1996. [ABSTRACT FROM AUTHOR]

Volcanic plume composition is strongly influenced by both changes in magmatic systems and plume-atmosphere interactions. Understanding the degassing mechanisms controlling the type of volcanic activity implies deciphering the contributions of magmatic gases reaching the surface and their posterior chemical transformations in contact with the atmosphere. Remote sensing techniques based on direct solar absorption spectroscopy provide valuable information about most of the emitted magmatic gases but also on gas species formed and converted within the plumes. In this study, we explore the procedures, performances and benefits of combining two direct solar absorption techniques, high resolution Fourier Transform Infrared Spectroscopy (FTIR) and Ultraviolet Differential Optical Absorption Spectroscopy (UV-DOAS), to observe the composition changes in the Popocatépetl’s plume with high temporal resolution. The SO2 vertical columns obtained from three instruments (DOAS, high resolution FTIR and Pandora) were found similar (median difference

Las anomalías geofísicas de diferente naturaleza observadas en el área del volcán Popocatépetl se presentan y analizan en este artículo. Las anomalías encontradas son de origen volcánico. El ambiente electromagnético en las cercanías del volcán resultaron tener más ruido que las estaciones de referencia; una fuerte actividad geomagnética similar al ruido fue observada en la componente H; además solamente se detectaron pulsaciones geomagnéticas en la estación Tlamacas (localizada a 4 km del volcán). Algunos cambios notables en la evolución del índice fractal calculado para el campo geomagnético pueden estar conectados a la presencia de procesos críticos, los cuales pueden estar ocurriendo en la dinámica del volcán. doi: https://doi.org/10.22201/igeof.00167169p.2018.58.2.1953

En este ensayo fotográfico mostramos parte del ritual que los habitantes de Santiago Xalitzintla (México) realizan al volcán Popocatépetl. La celebración de su cumpleaños, 12 de marzo, revela las prácticas comunitarias para mantener una relación de reciprocidad con el volcán, y controlar con ello su fuerza eruptiva.

El volcán Popocatépetl, ubicado en la parte central de México, se encuentra rodeado por una región densamente poblada que excede los 20 millones de habitantes. Su actividad histórica de los últimos 500 años se ha limitado a varias erupciones de pequeñas a moderadas, análogas al episodio actual (1994 al presente). Sin embargo, desde la destrucción del cono ancestral hace unos 23 000 años B.P., el Popocatépetl ha dado lugar a una amplia gama de erupciones tanto en tamaño como en tipo, incluyendo eventos plinianos y colapsos masivos de sector. Muchas de las erupciones mayores han dado lugar a grandes volúmenes de material de caída de tefra que se han extendido al menos unos 20 kilómetros hacia el sureste, entre 10 y 15 kilómetros al noreste y 15 a 18 kilómetros en el sector oeste. Sin embargo, la mayoría de los eventos plinianos cubrieron áreas más extensas con material de caída de pómez, flujos de piroclásticos y depósitos de lahar. Basados en la distribución actual de población y de los asentamientos humanos, y considerando la experiencia de evacuación efectuada durante los picos de actividad volcánica, en este trabajo se ha desarrollado una evaluación del riesgo basado en la vulnerabilidad de las áreas amenazadas alrededor del Popocatépetl, con la finalidad de apoyar la toma de decisiones ante una potencial crisis volcánica. doi: https://doi.org/10.22201/igeof.00167169p.2019.58.1.2064

Existen discursos y prácticas diversas de la población y el gobierno sobre un tema importante de política pública como es el de protección civil. En primer lugar se revisa la noción de riesgo según las ciencias sociales y las políticas de protección civil. En segundo, las miradas en torno al riesgo volcánico del Popocatépetl en Amecameca y se remarcan algunas narrativas populares sobre el tema que presentan cierta distancia del discurso científico técnico, lo cual se hace a través de los datos obtenidos de una encuesta y especialmente de entrevistas que se aplicaron a la población. Entre los resultados es posible ver la distancia entre miradas y discursos en relación con el riesgo del volcán.

The "Lorenzo pumice" (LP) fallout was produced by a Plinian (VEI = 4) eruption of Popocatépetl volcano ∼40 cal BCE during the Terminal Preclassic period. It is part of a pyroclastic sequence that consists in stratigraphic order of fall, pyroclastic density current, and lahar deposits, which in turn are partly covered by the 70 km2 andesitic-dacitic "Pedregal de Nealtican" lava flow field on the eastern slope of the volcano. The composition of the pumice varies insignificantly (SiO 2 = 61.0 to 63.5 wt%) with phenocrysts of euhedral plagioclase > orthopyroxene > clinopyroxene ± olivine ± hornblende ± opaques. Sizes of lithics and the isopach map indicate an eruption column height of ∼28 km and a dispersal axis toward the ENE, where an area of ∼600 km2 that included pre-Hispanic dispersed villages was buried under >10 cm of pumice. The minimum volume for the LP fallout was calculated at ∼0.6 km3 corresponding to ∼0.2 km3 of dense rock equivalent (DRE). The short Plinian phase ended when the column collapsed abruptly, generating lethal pyroclastic density currents that were emplaced around the volcano. It was followed by periodic flooding by rain lahars that originated from the slopes of Popocatépetl and from neighboring Iztaccíhuatl, severely affecting ravines and large portions of the plains of Puebla in the east. After the cataclysmic phase, the El Ombligo vent alignment opened at ∼4000 m a.s.l. on Popocatépetl's NE upper slope from which the lavas that form the Nealtican lava flow field emanated, an effusive activity that lasted >30 years. Paleomagnetic data for these lavas and stratigraphic evidence indicate that the lava flows with a total volume of 4.2 km3 were emplaced shortly after the explosive Plinian phase and represent the degassed portion of the LP magma. This eruption had a considerable impact on pre-Hispanic settlements around the volcano, whose population exodus and relocation probably contributed to the rise of important cities in central Mexico, such as Teotihuacán, Cholula, and Cantona. • The Lorenzo Plinian eruption (VEI = 4) of Popocatépetl at ∼40 cal BC covered >600 km2 with a >10-cm-thick pumice deposit • Subsequently, the 70 km2 Nealtican lava flow field (4.2 km3) formed over ∼30 years and represents the degassed magma • Lahars flooded ∼1900 km2 affecting agricultural areas and were the main contributor to a massive population exodus [ABSTRACT FROM AUTHOR]

How do lava domes release volcanic gases? Studying this problem is crucial to understand, and potentially anticipate, the generation of the sudden and dangerous explosive eruptions that frequently accompany dome extrusions. Since its awakening in 1994, Popocatépetl volcano has produced more than 50 lava domes and has been consistently among the strongest permanent emitters of volcanic gases. In this work, we have characterized the passive and explosive degassing between 2013 and 2016 at a high time resolution using an SO2 camera, to achieve a better understanding of the conduit processes. Our 4-year average SO2 flux is 45 kg/s, in line with the long-term average of the whole current eruptive period. We show that Popocatépetl volcano is essentially an open system and that passive degassing, i.e., degassing with no associated emission of lava or ash, dominates >95% of the time. This passive degassing is continuous and sustained, whether the crater contains a lava dome or not. It shows most of the time a strong periodic component, with a pseudo-period of ~5 min, and amplitudes of 30 to 60% of the average value. We could distinguish two types of explosions based on their SO2 flux patterns. The first type (E1) occurs in the middle of the normal passive degassing and is followed by a rapid return of the SO2 flux down to its pre-explosive level. The second type (E2), which corresponds to the strongest events, is anticipated by a rapid decrease of the SO2 flux to abnormally low values and is followed by a return to its normal values. The E2 explosions are probably caused by the accumulation of gas below a rapidly compacting permeable dome. We suggest that transient episodes of gravitational compaction of the usually permeable dome and the upper conduit is the only mechanism that is fast enough to explain the sharp decrease of the SO2 flux that anticipates the E2 explosions. Our model is potentially applicable to a large number of andesitic volcanoes that undergo passive degassing interspersed with short-lived explosions.

We present high‐broadband infrasound (0.01–100 Hz; 200‐Hz sample rate) observations of Vulcanian explosions at Popocatépetl volcano, Mexico. Popocatépetl is a highly active andesitic stratovolcano with regular violent explosions, making it a promising target for seismoacoustic observations. We deployed a four‐element broadband infrasound array (aperture 50 m) colocated with a compact broadband (120 s) seismometer at a site (ATLI) 15.8 km to the east‐southeast of Popocatépetl's summit. We highlight waveform examples from five powerful explosions during October to December 2017 that produced infrasound zero‐to‐peak pressure amplitudes ranging from 30 to 100 Pa at ATLI. The infrasound waveforms are highly asymmetric and are associated with clear air‐ground‐coupled arrivals on seismometers, with inverted vertical displacement waveforms tracking infrasonic pressure waveforms. Popocatépetl is close to major population centers, and array processing reveals persistent background infrasound from multiple directions, presumably of anthropogenic origin; our results have implications for infrasound monitoring at populated volcanoes. Plain Language Summary: Seismology and acoustics are complementary methods for quantifying volcanic eruption processes, corresponding to elastic wavefields propagating through the solid Earth and acoustic wavefields propagating through the fluid atmosphere, respectively. Seismic data currently form the backbone of most volcano‐monitoring systems. Seismic signals at erupting volcanoes capture subsurface magma transport and rapid depressurization associated with explosive eruptions. Infrasound (acoustic waves with frequencies below 20 Hz, the lower‐frequency limit of human hearing) is a newer technology; infrasound data record subaerial degassing and allow physical quantification of explosive eruption mechanisms. Popocatépetl is one of the two most active volcanoes in Mexico (together with Volcán de Colima) and a prodigious source of explosive activity, making it an obvious target for combined seismic and infrasound (seismoacoustic) observations. We recorded continuous infrasound and seismic waveform data at a site 15.8 km to the east‐southeast of Popocatépetl for several months, capturing five powerful explosions. Our data were collected at a location where local people report hearing sounds associated with visual observations of explosions from Popocatépetl. Part of the motivation of this work is to investigate the capability of infrasound stations at distances greater than 5 km to monitor Popocatépetl with significantly reduced risk exposure to field personnel and instrumentation. Key Points: Infrasound array study of Popocatépetl; high broadband (200‐Hz sample rate) includes sub‐bass rangeVulcanian explosions produce high‐amplitude asymmetric infrasound, which is air‐ground coupledInverted vertical displacement seismic waveforms track infrasonic pressure waveforms [ABSTRACT FROM AUTHOR]

Situated above multiple tectonic plates, central Mexico and highland Guatemala often experience strong earthquakes and volcanic activity. During the sixteenth to eighteenth centuries, this unpredictable topography shaped the human interactions with the natural environment. While indigenous populations in these regions were familiar with this terrain, Spanish colonists struggled to make sense of this volcanic topography upon their arrival. This field report provides an overview of 4 months of dissertation research completed during fall 2017 in Mexico City, Puebla, and Tetela del Volcán. This research occurred in the aftermath of a 7.1 earthquake, measured on the Moment Magnitude scale, that struck central Mexico 2 weeks after my arrival. This essay discusses the realities of living in post-earthquake Mexico and the archival research undertaken in each city. Preliminary findings reveal that knowledge concerning the volcanic topography influenced the outcome of property conflicts in favor of indigenous litigants. Research for this project will continue throughout 2018 in Spain and Guatemala. [ABSTRACT FROM AUTHOR]

Copyright of Avian Conservation & Ecology is the property of Resilience Alliance and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

There are different speeches and practices told by people and government on an important public policy issue such as civil protection. First, in this paper, the notion of risk, according to Social Sciences is reviewed, as well as the civil protection policies. Secondly, the look around the risk around Popocatepetl volcano in Amecameca and some popular narratives that present some distance from the technical scientific discourse are remarked. This is done through some data and results from a survey applied in this place and interviews that were done among the population. The results indicate it is possible to see the distance between the expressions, glances and speeches regarding the volcano risk. [ABSTRACT FROM AUTHOR]

The following work shows a study about the recent activity of the Popocatepetl volcano, analyzing images of the eruptive columns of the same and supported by terrestrial and satellite photogrammetry tools for their classification; the emanation of gases, ashes, height and direction were calculated. After 67 years, on December 21, 1994 the volcano had an eruptive activity. The columns reached up to 3 km altitude, the ash emission increased and the seismometers indicated tremors of the movement of the magma in the structure. This event marked the reactivation of the volcano, this study shows an analysis of the surface and perimeter of the crater, to determine the deformations that it has suffered until 2016 generated by the activity that the volcano has experienced; for this study, satellite images and application of specialized software for its processing were used. [ABSTRACT FROM AUTHOR]

The investigation of the dynamics of the continuous geomagnetic signal recorded at Popocatepetl volcano from 1997 to 1999 was performed using the Fisher–Shannon approach, a statistical tool for identifying dynamic changes in complex systems. Our results reveal that dynamic changes in the Total Magnetic Field (TMF) are correlated with different stress states of the magmatic setting and the plumbing system in the volcano. The results contribute to reveal the probable signatures of the thermal processes involved in the movement of the magma that induce the variations of the TMF signal. [ABSTRACT FROM AUTHOR]

The processes linked with the emplacement and growth/destruction of a lava dome are of prime importance to understand the stability of such extrusions and assess the associated risks for local populations. During the last couple of decades, ground and space-based spectroscopic techniques have been developed to monitor such processes from a safe distance. Such approaches significantly improved our knowledge about the relationship between the chemical composition of the volcanic gas plumes and both the deep and shallow volcanic processes leading to the different types of explosive activity. The potential of the ground-based thermal emission Fourier Transform Infrared spectroscopy (FTIR) remained under-exploited due to the difficulty to properly handle the radiative-transfer phenomena. Despite the drawbacks in the complex analytical requirements, this method enables to continuously monitor (day and night) with a high temporal resolution (1 meas/3 min), relevant gas species such as SO 2 and SiF 4 in the volcanic plumes. Previous studies have related the temporal variations of the SiF 4 /SO 2 ratio in volcanic plumes to the onset of vulcanian explosions. This study reports a 6-month SO 2 , SiF 4, and SiF 4 /SO 2 time series (from January to June 2015) of the Popocatepetl's gas plume obtained from FTIR thermal emission spectroscopic measurements. The infrared spectra were analyzed using the SFIT4 radiative transfer and inverse model, which we have adapted for this application. We obtained highly variable SiF 4 /SO 2 ratios with a mean value of 3.6 × 10 − 4 , with the highest values (around 3 × 10 − 3 ) measured during the final phase of a lava dome growth (February–March 2015). The rapid SiF 4 /SO 2 variations were more carefully explored and compared for the first time with the seismic activity. A remarkable coincidence between sharp SiF 4 /SO 2 rises and the seismic events are evidenced here. [ABSTRACT FROM AUTHOR]

The White Pumice (WP) is one of the thickest and most voluminous Plinian fallouts produced by Popocatépetl volcano in central Mexico during the Late Pleistocene-Holocene. Its eruption ~ 23,500 14 C y BP (27,800 cal BP) was triggered by the catastrophic failure of the SW flank of the volcano. The resulting debris avalanche was highly mobile reaching 72 km from the cone with an apparent coefficient of friction (L/H) of 0.06. The deposit covers an area of ~ 1200 km 2 , and has a volume of 10.4 km 3 . This gigantic landslide, characterized by exceptionally large proximal hummocks (> 400 m) provoked the sudden decompression of the hydrothermal and magmatic systems, which produced an initial blast followed by the rise of a Plinian column that reached an altitude of ~ 33 km. The isopach map allows the recognition of a dispersal axis pointing toward the south, where an area of ~ 2490 km 2 was covered by > 10 cm of pumice and ash. The total volume of the pumice fallout was estimated at ~ 1.9 km 3 DRE (Dense Rock Equivalent). Pumice clasts are dacitic (62–66 wt.% SiO 2 , anhydrous basis), highly vesicular (55–88 vol.%) and display a seriate texture with phenocrysts of plagioclase + hornblende + augite + hypersthene + oxides (Ti-magnetite and ilmenite) + apatite. As the eruption advanced, discharge rates became more intermittent and the height of the column fluctuated and finally collapsed, generating pumice-and-ash flows that were emplaced around the volcano. This short but intense activity was followed during subsequent years by rain-induced lahars that reached great distances from the volcano. At the same time, more degassed andesitic-dacitic (61–65 wt.% SiO 2 ) magma was erupted effusively (4.4 km 3 , DRE) in the new horseshoe-shaped ~ 5 km-wide crater from which the Tochimilco lava flow descended toward the SSE, where it inundated an area of ~ 68 km 2 and reached as far as ~ 22 km from its source. Since then, multiple eruptions have reconstructed the summit cone, almost completely obliterating the horseshoe-shaped crater. During the course of this catastrophic eruption (VEI = 5) a total volume of ~ 6.3 km 3 (DRE) of juvenile magma (pumice and lava) were emitted and at least an additional ~ 10 km 3 of pre-existing rocks (debris avalanche) mobilized. It surpasses in magnitude most other known Plinian eruptions from Popocatépetl and can be envisaged as an example of a worst-case scenario for hazard evaluation purposes. It dramatically changed the morphology of the volcano and had profound and far-reaching effects beyond its immediate vicinity along rivers draining surrounding plains as well as on the lacustrine basins (e.g. Chalco) to the NE. A repeat of such an eruption in this densely populated area would certainly cause a major calamity of unprecedented dimensions. [ABSTRACT FROM AUTHOR]

Most hummingbird species are distributed in tropical lowlands and mountains with few species reaching the alpine environments of high mountain peaks. Field surveys were conducted in nine alpine sites across four of the highest volcanoes in central Mexico for three years to document hummingbird occurrence, habitat use, and some aspects of behavior. We also searched through historical museum collections and online databases to document early records of hummingbirds in Mexican alpine habitats. In addition, we conducted a search through historical herbarium collections of ornithophilous plant species in alpine habitats, and a literature search on glacier retreats in Mexico to establish past and present elevational limits of alpine vegetation. We recorded the presence of four hummingbird species using floral resources across the nine study sites: Cynanthus latirostris (Broad-billed Hummingbird), Hylocharis leucotis (White-eared Hummingbird), Lampornis clemenciae (Blue-throated Hummingbird), and Selasphorus platycercus (Broad-tailed Hummingbird). The latter two species were recorded frequently throughout the growing season (May-October), whereas C. latirostris was observed on one day in July, and H. leucotis on two days in April and May. Three of the four species were observed foraging from Castilleja tolucensis, an alpine Mexican endemic herb, at 4428 m above sea level, and all four species foraged from Penstemon gentianoides at the lower alpine sites 3900-4100. At the highest elevations, we observed hummingbirds hovering and perching on rocks while feeding from flowers at ground level. Both male and female of L. clemenciae and S. platycercus were present at patches of P. gentianoides; however, with S. platycercus, males accounted for more than 80% of the individuals observed and more than 95% of individuals observed at the highest elevations. Additionally, a survey of historical records from museum collections and bird sightings from e-databases revealed only three early records of hummingbirds in alpine sites, with only one observed earlier than 1987. This suggests that hummingbirds were not recorded earlier in alpine habitats because of a lack of sampling. Nevertheless, evidence from glacial retreats and plant distributions along an elevational gradient also indicate that hummingbirds have expanded their elevational range as new habitats have opened up for colonization associated with global climate change. The results reported here are the first records of the four hummingbird species in the Mexican alpine grassland and one of the highest altitudinal records for hummingbirds in North America. We discuss the importance and conservation implications of alpine ecosystems in Mexico as habitats for hummingbirds.

Se presentan los resultados del monitoreo de HCO - y pH en manantiales del volcán Popocatépetl durante seis años del actual periodo eruptivo. Los pequeños picos en HCO - y P en manantiales se asocian a ascensos de pulsos pequeños de magma en el Popocatépetl. El magma proporciona fluidos ricos en CO2 al sistema hidrológico que es controlado por recarga meteórica. La PCO2 en equilibrio con los manantiales es de 2 a 4 órdenes de magnitud mayor al de agua saturada con aire. La alta presión de CO2 también sugiere una interacción directa con los fluidos magmáticos. Los isótopos de carbono apoyan un origen principalmente magmático para el CO2 disuelto. doi: https://doi.org/10.22201/igeof.00167169p.2002.41.3.354

Se efectuaron determinaciones de radón en suelos alrededor del volcán Popocatépetl de septiembre 1997 a abril 1999. El gas del suelo se muestreó con un tubo de acero inoxidable y se midió en el campo con un contador de centelleo de partículas alfa. En uno de los sitios se correlacionaron las variaciones de las concentraciones de 222Rn con los cambios en la actividad volcánica. Por otro lado, se sabe que las variaciones en las características químicas de manantiales en volcanes activos pueden utilizarse para el monitoreo volcánico. En 1993 inició un período de actividad del volcán Popocatépetl. Desde 1995, el análisis químico de manan- tiales ha sido incluido dentro de la vigilancia volcánica. En el campo se midieron la conductancia, el pH y la temperatura. Las concentraciones de iones principales HCO -, Cl-, SO 2-, Mg2+, Na+, K+, Ca2+ se determinaron en el laboratorio por métodos estándares. Observaron incrementos de las concentraciones de B, SO 2- y Cl- antes de algunos cambios en la actividad, en algunos manantiales. Se encontró que las anomalías de radón coincidieron aproximadamente con algunas de las variaciones químicas. Los niveles más altos de 222Rn en uno de los sitios se obtuvieron en el período que precedió a la erupción del 24 de diciembre de 1997, la cual incluyó la emisión de fragmentos de tefra relativamente grandes. doi: https://doi.org/10.22201/igeof.00167169p.2002.41.3.342

Measurements of radon in soil gas were carried out around Popocatépetl volcano during the period from September 1997 to April 1999. Soil gas was sampled using a stainless steel probe, and measured in the field with an alpha scintillation counter. At one location concentration variations of 222Rn in soil have been related with changes in the volcanic activity. In addition, chemical variations of spring waters at active volcanoes may be useful for volcano monitoring. In 1993 an increased period of volcanic activity began at Popocatépetl volcano. Since 1995, the chemical analyses of springs have been carried out as part of the surveillance of the volcanic activity. Conductivity, pH, and temperature were measured in the field. Concentration of the major ions: HCO3-, Cl- , SO42-, Mg2+, Na+, K+, Ca2+ have been determined in the laboratory by standard methods. The minor species boron, sulfide and fluoride were analyzed by colorimetry and potentiometry. Concentration increases of B, SO42-, and Cl-, have been observed preceding some changes in volcanic activity during the studied period in some of the springs. Radon anomalies were found to approximately coincide with some of the chemical variations. The highest 222Rn levels at one location were measured during the period that preceded the eruption that occurred on December 24, 1997, which included the emission of relatively large tephra fragments.

Ultraviolet SO 2 cameras are increasingly used in volcanology because of their ability to remotely measure the 2D distribution of SO 2 in volcanic plumes, at a high frequency. However, light dilution, i.e., the scattering of ambient photons within the instrument's field of view (FoV) on air parcels located between the plume and the instrument, induces a systematic underestimation of the measurements, whose magnitude increases with distance, SO 2 content, atmospheric pressure and turbidity. Here we describe a robust and straightforward method to quantify and correct this effect. We retrieve atmospheric scattering coefficients based on the contrast attenuation between the sky and the increasingly distant slope of the volcanic edifice. We illustrate our method with a case study at Etna volcano, where difference between corrected and uncorrected emission rates amounts to 40% to 80%, and investigate the temporal variations of the scattering coefficient during 1 h of measurements on Etna. We validate the correction method at Popocatépetl volcano by performing measurements of the same plume at different distances from the volcano. Finally, we reported the atmospheric scattering coefficients for several volcanoes at different latitudes and altitudes. [ABSTRACT FROM AUTHOR]

In the last eruptive period of Popocatépetl volcano (19° 02'N, 98° 37' W, 5424 m) several syn-eruptive lahars modified the fluvial network of the northeastern slope, where the Huiloac River is located. The lahars that produced the most important morphological changes took place in 1997 and 2001. Although some explosive events have taken place since then, such as the recent eruptions of May and June 2013, lahars related to volcanic activity have not been recorded in Huiloac gorge. This article proposes a methodology to detect and quantify morphological changes and to determine the dynamics of erosion and sedimentary processes in a section of Huiloac gorgefor the first seven years after the syn-eruptive lahar of 2001. This method combines the interpretation of a temporal series ofgeomorphological maps and topographic profiles across the channel using CAD (Computer-aided design) and GIS (Geographic Information Systems). Finally, the analysis of the geomorphic and topographic evolution is cross-referenced with available information on rainfall. The results show that the initial phase (up until October 2002) is characterized by incision and removal of the material that filled the river bed during the 2001 lahar. Afterwards, the geomorphological action of running water and the dynamics of slopes widened and deepened the channel, although sedimentation occurred as well, as evidenced by river-banks and lahar terraces. The frequency and capacity of secondary lahars, fed by rainfall and glacier melt water, are the factors that determine the domain of erosion or sedimentation in Huiloac. Thus, it has been observed that in seasons with less rain and regular precipitation, fewer morphological variations occurred and a smaller amount of material was eroded, such as in the period 2004 - 2006. On the other hand, exceptional rainfall in the dry season (January 2002 and January 2004) or continuous rains at the end of the wet season (September and October 2007) triggered processes of erosion by incision, lateral erosion, and removal of the laharic deposits. It can be concluded, at the end of this first period of observation, that despite considerable erosion, the riverbed is still unstable due to steep slopes on the sides of the river. [ABSTRACT FROM AUTHOR]

This paper presents a new seismic velocity model (P- and S-wave velocities and Vp/Vs ratio) beneath the Popocatépetl volcano to a depth of ~4kmbelow sea level (bsl). This model is based on the tomographic inversion of P- and S-wave arrival time data from earthquakes in the region of the volcano. These data were recorded by the 15 stations of a temporary seismic network that was deployed on the volcano in 1999 and 2000. The recording period was during a relatively quiet period between two strong eruptions, which occurred before and after the experiment. This period is characterized by low levels of volcano-related seismicity. Most of the recorded events occurred across an area much larger than the network. In this study, we conducted several synthetic tests, which validate the use of the out-of-network events to improve the resolution of the tomographic inversion beneath the stations. In the resulting model, we see that the main volcanic edifice is associated with high velocities that have a mushroom shape and that these high velocities are most prominent in the P-wave model. This feature may indicate the presence of overpressured solidified igneous rocks, which comprise the edifice of Popocatépetl. Below the summit of the volcano, we observe a prominent high Vp/Vs anomaly, which reaches a value of 1.9. This anomaly probably indicates the existence of cracks and pores filled with melts and fluids, and it may represent a fracture zone that serves as a conduit feeding the volcano. This model characterizes the interior structure of the Popocatépetl volcano prior to the strong September 2000 eruption, which occurred a few months after the termination of the experiment. [ABSTRACT FROM AUTHOR]

Volcán Popocatépetl has explosively erupted in Plinian style at least five times in the last 23,000 years. Extreme deviations in composition and the occurrence of dissolution features in plagioclase and pyroxene, and the occasional presence of xenocrysts of Cr-rich Fe-Ti oxides and Mg-rich olivines and pyroxenes indicate that magma mixing has been a major process affecting the magmatic system. The nearly invariant composition of the erupted products (andesitic-dacitic) suggests, however, that mixing is not acting alone and must be balanced by assimilation and/or crystallization. To investigate the magmatic processes that have modified the Plinian magmas, textural and compositional variations and growth rates in plagioclase were used to approximate the frequency of mixing events affecting each magma. Systematic analysis of Sr, Nd, and Pb isotopes was carried out on plagioclase, pyroxene, and pumice matrix glass to constrain the extent of assimilation of upper crustal rocks. Additionally, a series of phase equilibrium experiments were carried out to constrain the depth where such mixing and assimilation occurred. We find that magma was stored at one of two different depths beneath Popocatépetl with magma mixing acting in both reservoirs. Mixing frequency and the relative impact on mineral compositions and textures has varied with time. Assimilation of calcareous rocks underneath Popocatépetl has not been pervasive and does not contribute significantly to the evolution of the Plinian magmas. The similar compositions of magmas with diverse mixing histories suggest that fractional crystallization, and possibly assimilation of deep crust, takes place at depth and that intermediate magmas ascend into the upper crust already differentiated. [ABSTRACT FROM AUTHOR]

Popocatépetl is one of Mexico's most active volcanoes threatening a densely populated area that includes Mexico City with more than 20 million inhabitants. The destructive potential of this volcano is demonstrated by its Late Pleistocene-Holocene eruptive activity, which has been characterized by recurrent Plinian eruptions of large magnitude, the last two of which destroyed human settlements in pre-Hispanic times. Popocatépetl's reawakening in 1994 produced a crisis that culminated with the evacuation of two villages on the northeastern flank of the volcano. Shortly after, a monitoring system and a civil protection contingency plan based on a hazard zone map were implemented. The current volcanic hazards map considers the potential occurrence of different volcanic phenomena, including pyroclastic density currents and lahars. However, no quantitative assessment of the tephra hazard, especially related to atmospheric dispersal, has been performed. The presence of airborne volcanic ash at low and jet-cruise atmospheric levels compromises the safety of aircraft operations and forces re-routing of aircraft to prevent encounters with volcanic ash clouds. Given the high number of important airports in the surroundings of Popocatépetl volcano and considering the potential threat posed to civil aviation in Mexico and adjacent regions in case of a Plinian eruption, a hazard assessment for tephra dispersal is required. In this work, we present the first probabilistic tephra dispersal hazard assessment for Popocatépetl volcano. We compute probabilistic hazard maps for critical thresholds of airborne ash concentrations at different flight levels, corresponding to the situation defined in Europe during 2010, and still under discussion. Tephra dispersal mode is performed using the FALL3D numerical model. Probabilistic hazard maps are built for a Plinian eruptive scenario defined on the basis of geological field data for the 'Ochre Pumice' Plinian eruption (4965 C yr BP). FALL3D model input eruptive parameters are constrained through an inversion method carried out with the semi-analytical HAZMAP model and are varied by sampling them using probability density functions. We analyze the influence of seasonal variations on ash dispersal and estimate the average persistence of critical ash concentrations at relevant locations and airports. This study assesses the impact that a Plinian eruption similar to the Ochre Pumice eruption would have on the main airports of Mexico and adjacent areas. The hazard maps presented here can support long-term planning that would help minimize the impacts of such an eruption on civil aviation. [ABSTRACT FROM AUTHOR]

Abstract: Volcán Popocatépetl (México) erupted ~14,100 14 Cyr BP (~17,000calyr BP) producing the Tutti Frutti Plinian Eruption (TFPE). The eruption tapped two different silicic magmas (GT and MT) that mixed just prior and during the eruption, resulting in the collapse of the reservoir and formation of a caldera. Two fall deposits (GT and MT) and two series of pyroclastic flows (P01 and P02) were emplaced during the eruption. These were studied at 91 sites, where thicknesses were measured, and at many sites the five coarsest lithics observed in each unit were measured. Several samples from deposits were sieved for component analysis. The eruption began with intermittent, short lived eruptions that deposited the GT unit at proximal sites around the volcano. Next, the main Plinian phase of the eruption started, and the MT unit and a pyroclastic flow were deposited to the northwest of the present-day cone. Overall, ~3km3 of magma were erupted. The pyroclastic flow within MT separates two fall units characterized by different pumice color and lithic content. During deposition of the lower unit (milky pumice) eruptive intensity reached 3×108 kgs−1, producing a Plinian column 37±2km in height. After emplacement of the pyroclastic flow, a lithic-rich upper unit (orange pumice) was deposited with a peak intensity of 5×108 kgs−1, producing a Plinian column 44±2km in height. Lithics in the TFPE vary from only volcanic (~5vol.%) in GT, to volcanic, granodiorite, and metamorphic (up to 50vol.%) in MT. The shift in components and lithic content was produced by the collapse of the reservoir. We suggest that the reservoir was over-pressured because of mixing between GT and MT magmas, and then relaxed when all of GT, and part of MT magma were tapped, triggering collapse. The characteristics of mixing were elucidated by studying banded pumice and mixed populations of crystals found in pumice from both units. In addition, the occurrence of An-rich plagioclase, Mg-rich pyroxene, and Cr-rich magnetite crystals revealed intimate mixing of more mafic magma with MT. [Copyright &y& Elsevier]

This paper traces the origins and development of a little-known extractive industry in nineteenth-century Mexico: volcanic sulphur mining. Unpublished documents from Mexican archives, nineteenth-century travel literature, reports from early scientific expeditions, and historical newspapers provide the bulk of data. Documents show how both Mexican and United States interests -- indigenous sulphur miners (azufreros) and venture capitalists -- confronted the challenges of mining sulphur from the crater of Mexico's Popoeatépetl volcano, at 5,426 meters (17,802 feet) elevation. [ABSTRACT FROM AUTHOR]

Abstract: Colima and Popocatépetl volcanoes began erupting during the second half of the twentieth century after periods or relatively long quiescence. Both eruptive episodes show similarities: persistent dome growth and destruction episodes over periods of decades, and differences: higher rates of magma and gas production at Popocatépetl, with similar magmas (Popocatépetl''s slightly more acidic). We use a simplified equation of state (EOS) for calculating the density of the hydrous andesitic magmas of Volcán de Colima in a realistic range of pressures, temperatures and dissolved water content to model the density contrast with the host rock causing buoyancy of the magmatic column. We use this model to explain some aspects of the dome-forming effusive activity of Colima, and compare the results with a similar study made in a previous work on Popocatépetl. This dome-height isostatic model explains well the observed mean heights (around 50m) of the Colima lava domes with the buoyant force resulting from a 2.5wt.% H2O content in the melt, a value consistent with recently published measurements of rock inclusions. The slightly higher H2O contents required for the observed dome heights at Popocatépetl is explained in terms of the different depths of the isostatic compensation levels, the compositional differences between the magmas, and the structural differences between the volcanic edifices. [Copyright &y& Elsevier]

The Miocene–Quaternary Trans-Mexican Volcanic arc is thought to have grown southwards (i.e. trenchward) since the Pliocene. This theory is mainly supported by roughly N–S-directed polygenetic volcanic ranges along which volcanic activity migrates southwards with time. We investigated the eruptive history of one of these ranges, the Sierra Nevada (east boundary of Mexico City basin), by compiling literature ages and providing new K–Ar dates. Our K–Ar ages are the first ones for the northernmost Tláloc and Telapón volcanoes and for the ancestral Popocatépetl (Nexpayantla). The obtained ages reveal that the four stratovolcanoes forming the range worked contemporaneously during most of the Middle to Late Pleistocene. However, taking into account the onset of the volcanic activity, a southward migration is evidenced along the Sierra Nevada: volcanism initiated at its northern tip at least 1.8 Ma ago at Tláloc volcano, extended southwards 1 Ma ago with Iztaccíhuatl and appeared at its southern end 329 ka ago with the Nexpayantla cone. Such a migration would be most probably primarily driven by Cocos slab roll-back and steepening rather than by regional crustal tectonics, which played a secondary role by controlling the apparent alignment of the volcanoes. [ABSTRACT FROM PUBLISHER]

Abstract: We performed the first 3D seismic tomography of the Popocatépetl volcano, Mexico, from the inversion of the P-wave arrival times of nearly 1500 earthquakes recorded by up to 11 seismic stations of the permanent CENAPRED-SSN network. We used the Bayesian tomographic algorithm developed by Monteiller et al. (2005) to perform this P-wave travel-time tomography and carefully choose optimal regularization hyper-parameters. Sensitivity tests show that the inversion is correctly constrained under the volcano from −1 to 4km depth b.s.l.. At these depths, the optimal tomographic model mainly shows low-velocity volumes surrounded by higher-velocity volumes. Lateral heterogeneity is strong: the variation of the P-wave velocity may reach up to ±20% of the average value at a given depth. Low-velocity volumes correlate well with results from former geological and geophysical studies. [Copyright &y& Elsevier]

Abstract: On December 1, 2007, the solar absorption infrared spectra of the Popocatépetl volcanic plume was recorded during an eruptive event and complementarily on November 17, 2008, the passive quiescent degassing was measured from the same site. A portable FTIR spectrometer with a scanning mirror for fast tracking of the sun provided the flexibility, quality, and simplicity needed for field deployment. Slant columns of the gases SO2, HCl, HF, and SiF4 were retrieved and strong differences could be observed when comparing gas ratios in both time periods. During the explosive eruption, the SO2/HCl ratio was three times greater and the HF/HCl ratio was slightly smaller than during passive degassing. While the ratios among SO2, HCl, HF, and SiF4 describe the chemical composition of the volcanic gas mixture, the SiF4/HF ratio provides information about the equilibrium temperatures of the stored gases which in this study were calculated at 150° and 185°C for the explosive and quiescent degassing episodes, respectively. We conclude that cooling of lava domes in the crater precedes Vulcanian explosions as suggested by Schaaf et al (2005). Based on SO2 flux (Grutter et al., 2008) and measurements and data from the November 2008 event, the average fluxes for HCl, HF, SiF4, and F through quiescent degassing are estimated to be 204, 22.7, 9.8, and 31.7 tons/day, respectively. These values are similar to those reported by Love et al. (1998) more than 10yrs ago. [ABSTRACT FROM AUTHOR]

I want to dedicate this article about life, science and culture of the inhabitants around Popocatepetl, a living volcano, Puebla, Mexico. In addition, I formulated student research projects during autumn season and gave these to the six groups of students (each group consisting of four to six students), who were working under my guidance. They studied the social, religious and economic conditions of the inhabitants residing around and the vicinity of Popo. During three years of my stay as Professor in Chemistry and Biology Department of Universidad de las Americas, Puebla, I observed daily activities of Popocatepetl and described this experience here!. [ABSTRACT FROM AUTHOR]

Abstract: The Ochre Pumice (OP) Plinian fallout was produced by Popocatépetl volcano in central Mexico, during a major Plinian eruption that occurred 4965±65 14C yr BP (3700 BC). The OP is part of the Ochre Pumice Sequence (OPS), that consists of surge, fall, and pyroclastic flow deposits. The OP Plinian fallout shows a bimodal grain size distribution with poor to moderate sorting that improves progressively towards the upper beds. The juvenile component is mainly pumice (>83wt.%), whereas the accidental components consist of igneous, sedimentary, and metamorphic clasts from the walls of the magma chamber and/or conduit. The vesicularity of the pumice decreases from bottom to top of the stratigraphic sequence while the crystal and glass contents increase. This suggests increasing magma degassing prior and during the eruption. The chemical composition of the pumice varies insignificantly; at the base it is less evolved (SiO2 =61wt.%) and it becomes slightly more silicic towards the top (SiO2 =63wt.%). Pumice clasts have a crystallinity index that ranges between 10 and 25vol.% and display a seriate texture with phenocrysts of euhedral plagioclase (Pl)+clinopyroxene (Cpx)+orthopyroxene (Opx)+olivine (Ol)±oxide (Ox)±apatite (Ap). The size of the maximum lithic (2.5cm) at a horizontal distance of 19km indicates an eruption column height of 37–41km. The isopach map allows the recognition of a dispersal axis that points towards the NNE, where an area of ~300km2 was covered by >6cm of pumice and ash. A minimum volume for the OP Plinian fallout deposit was calculated using a minimum thickness of 6cm found at distal outcrops, and was estimated at ~4.9km3 which corresponds to 2km3 of dense rock equivalent (DRE). Stratigraphic relations indicate that the entire OPS was emplaced during a short time interval of a few days to weeks and consisted of three main different phases: phreato-magmatic, Plinian, and vulcanian. It started violently with the emplacement of surges and then culminated with the eruption of the OP fallout deposit. As the eruption advanced, discharge rates became more intermittent and the height of the column fluctuated and finally collapsed, generating pumice-and-ash flows that were emplaced around the volcano. This short but intense activity was followed during subsequent years by the growth of domes in the crater and the emplacement of block-and-ash-flows generated by vulcanian explosions. [Copyright &y& Elsevier]

Abstract: We present a simplified equation of state (EOS) for calculating the density of hydrous siliceous magmas in a range of pressures, temperatures and dissolved water content of interest to study several magma conduit processes. A simpler linear form and a more precise non-linear, yet simple form of the equation, both valid in the range 0 to 0.25 GPa, 800 to 1000 K, and 0 to 7 wt.% H2O are proposed for the dacitic and andesitic Popocatépetl magma melt compositions. We apply these equations to explain some aspects of the dome-forming effusive activity that has been observed at Popocatépetl volcano since 1996. This model poses a density reduction dependent mainly on the volatile contents of the magma filling the volcano conduit system as the driving buoyancy force causing magma extrusions and dome growth. [Copyright &y& Elsevier]

Abstract: The main ions, silica, boron and sulfide were analyzed by standard methods in samples from waters of several springs and a shallow well located around Popocatépetl volcano. Analyses of several chemical components allowed a geochemical monitoring of Popocatépetl activity from 1995 to 2004. Most samples were dilute and immature cold waters and only silica minerals were oversaturated in the springs and well water. The ratios of chemical species indicated water–rock interaction with plagioclases, evaporites and ferromagnesian minerals. The chemistry of the spring with the highest conductivity indicated water interaction with limestones. A small, increasing trend of silica and magnesium concentrations over the nine year period at all sampled sites seems to reflect the increase on the alteration processes, mainly of ferromagnesium minerals. Interaction of immature waters and volcanic CO2 with the silicate minerals may dissolve silica and magnesium, resulting in the observed slow concentration increase in most spring waters. The influence of volcanic activity was reflected as changes of different nature in the water chemistry, which may have been derived from direct interaction of diffuse volcanic gases with the aquifers, or by the opening of new pathways for water and gases through the reactivation of the fault system. It is likely that short-period fluctuations of the water chemistry, like those observed in the concentrations of chloride, boron, and, sometimes, fluoride and sulfate, reflect the interaction of highly-volatile magmatic gases with water. Longer term trends, like those observed in sulfate and CO2 may reflect slow accumulation by scrubbing of fault-transported or diffuse gases that would otherwise show large variations in open vents. Their further concentration reduction signals the decline of the source magma-mixing process. Not all sampled sites responded well to volcanic influence; the spring at Axocopan best correlated with the changes of volcanic activity. The fluctuations of water chemistry played a significant role in the assessment of the volcanic hazard. The most relevant chemical monitoring parameters, jointly with others, were used by decision makers in managing the Popocatépetl activity. [Copyright &y& Elsevier]

Abstract: We have operated a GPS network on Popocatépetl volcano since 1994 consisting of a total of 7 continuous GPS stations on its northern and southwestern flanks and one additional station in the vicinity of the volcano. The overall characteristic behavior of Popocatépetl volcano during this period can be described as a minimally deforming system, in sharp contrast with its essentially continuous visible eruptive activity. A north-component motion analysis, assuming a fixed North American plate, shows a close correspondence of the Popocatépetl sites to those of other regional GPS sites. Most of the large-deformation transients observed on the Popocatépetl sites are therefore not of magmatic origin, but instead reflect aseismic transients that have been recognized recently as part of the Mid-American Trench subduction process. The surface deformation record of Popocatépetl volcano therefore suggests a magmatic system that lacks a well-defined shallow magma chamber, where most of the magma storage, transport, and ascent is carried out via a network of deep-rooted conduits that eventually extend to the summit crater. In most cases, Popocatépetl seems to operate as a semi-open system, thereby preventing any significant pressure build-up. [Copyright &y& Elsevier]

Abstract: Volcanic eruptions and other potentially hazardous natural phenomena occur independently of any human actions. However, such phenomena can cause disasters when a society fails to foresee the hazardous manifestations and adopt adequate measures to reduce its vulnerability. One of the causes of such a failure is the lack of a consistent perception of the changing hazards posed by an ongoing eruption, i.e., with members of the scientific community, the Civil Protection authorities and the general public having diverging notions about what is occurring and what may happen. The problem of attaining a perception of risk as uniform as possible in a population measured in millions during an evolving eruption requires searching for communication tools that can describe—as simply as possible—the relations between the level of threat posed by the volcano, and the level of response of the authorities and the public. The hazards-warning system adopted at Popocatépetl Volcano, called the Volcanic Traffic Light Alert System (VTLAS), is a basic communications protocol that translates volcano threat into seven levels of preparedness for the emergency-management authorities, but only three levels of alert for the public (color coded green–yellow–red). The changing status of the volcano threat is represented as the most likely scenarios according to the opinions of an official scientific committee analyzing all available data. The implementation of the VTLAS was intended to reduce the possibility of ambiguous interpretations of intermediate levels by the endangered population. Although the VTLAS is imperfect and has not solved all problems involved in mass communication and decision-making during a volcanic crisis, it marks a significant advance in the management of volcanic crises in Mexico. [Copyright &y& Elsevier]