Ignacio Galindo

Overview of the 1997^2000 activity of Volcan de Colima, Mexico

Abstract This overview of the 1997–2000 activity of Volcan de Colima is designed to serve as an introduction to the Special Issue and a summary of the detailed studies that follow. New andesitic block lava was first sighted from a helicopter on the morning of 20 November 1998, forming a rapidly growing dome in the summit crater. Numerous antecedents to the appearance of the dome were recognized, starting more than a year in advance, including: (1) pronounced increases in S/Cl and δD values at summit fumaroles in mid-1997; (2) five earthquake swarms between November–December 1997 and October–November 1998, with hypocenters that ranged down to 8 km beneath the summit and became shallower as the eruption approached; (3) steady inflation of the volcano reflected in shortening of geodetic survey line lengths beginning in November–December 1997 and continuing until the start of the eruption; (4) air-borne correlation spectrometer measurements of SO2 that increased from the background values of

Near real-time satellite monitoring during the 1997-2000 activity of Volcán de Colima (México) and its relationship with seismic monitoring

Abstract The 1997–2000 activity of Volcan de Colima provided a unique opportunity for the joint analysis of satellite and seismic monitoring techniques. Three stages of volcanic activity were observed: pre-lava stage, stage of lava eruption, stage of explosive eruptions. Advanced Very High Resolution Radiometer satellite data provided observations of both summit thermal anomalies and ash emission. Daily monitoring of Volcan de Colima was performed using early morning or late night NOAA 12 and 14 satellite passes gathered in real time at our satellite ground receiving station. Seismic observations were carried out by the Red Sismica del Estado de Colima. Good correlations are observed between seismic activity and parameters monitored by satellite during the three stages. Five seismic swarms were recorded during the reactivation period. Four of the seismic swarms coincided with periods of increase in summit temperature and strong ash emissions. It is important to note that the ash emissions were observed a few days before the beginning of seismic swarms. The thermal saturation at the summit was reached a few hours after the beginning of lava effusion on November 20, 1998, and remained at this level until May 1999 even after the lava flow stopped in early February 1999. The lava front was also clearly identified as a source of thermal anomalies and ash plumes. Study of the summit temperature–ash emission relationship allowed us to classify the strong explosions of 1999–2000. The strongest explosion, on February 10, 1999, produced the largest, ash-rich plumes that were detected over a wide area (∼150 km 2 ) and near-saturation temperature anomalies (47.2, 48.4°C). The main limitation of volcano satellite monitoring occurs during overcast conditions. Clouds prevented us from monitoring the seismic swarm of July 1998 and the explosion of July 1999. This study shows that satellite monitoring on a near real-time basis is a powerful tool not only for research in volcanology but also as an aid for scientific committees to define probable eruption scenarios during volcanic crisis and for Civil Protection Authorities for risk mitigation due to ash emission and sudden heating of the crater without seismicity.

Airborne measurements of particle and gas emissions from the December 1994–January 1995 eruption of Popocatépetl volcano (Mexico)

Abstract Airborne and ground-based (correlation spectrometer, cascade impactor, and photoelectric counter together with intake filter probes) measurements are described for the volcanic emissions from Popocatepetl volcano (Mexico) from December 23, 1994 to January 28, 1995. Measurements of SO 2 restarted 48 h after the eruption onset of December 21, 1994. Maximum sulfur dioxide (4560 t d −1 ) plus 3.8×10 4 t d −1 of particulate matter were ejected on December 24, 1994. The maximum rate of ejection occurred coincidentally with the maximum amplitude of harmonic tremor and the maximum number of seismic type B events. Sulfur dioxide emission rates ranged from 1790 to 2070 t d −1 (December 23–24, 1994). Afterwards, sulfur dioxide emission rates clearly indicated a consistent decline. However, frequent gas and ash emission puffs exhibited SO 2 fluxes reaching values as high as 3060 t d −1 . The emission SO 2 baseline for the period of study (February 1994–January 1995) was about 1000 t d −1 . Ejection velocity of particulate matter was approximately 270 m s −1 reaching a height of about 2.5 km over the summit. The immediate aerosol dispersion area was estimated at 6.0×10 4 km 2 maximum. The microscopic structure of particles (aerosol and tephra) showed a fragile material, probably coming from weathered crustal layers. X-ray fluorescence and neutron-activation analysis from the impactor samples found the following elements: Si, Al, Ca, S, P, Cl, K, Ni, Fe, Ti, Sc, Cu, Zn, Mn, Sr, Cr, Co, Y, Br, Se, Ga, Rb, Hg and Pb. Morphological analysis shows that ash samples might be from pulverized basaltic rock indicating that the Popocatepetl eruption of December 21, 1994 was at low temperature. The microscopic structure of puff material showed substance aggregates consisted of fragile rock, water and adsorbed SO 2 . These aggregates were observed within water droplets of approximately 1 mm and even larger. Sulfur transformations in the droplets occurred intensively. Volcanic ash contained 5–6% of sulfur during the first expulsion hours. Elemental relative concentrations with respect to Al show that both Si and S have relative concentrations >1, i.e., 13.73 and 2.17, respectively in agreement with the photoelectric counter and COSPEC measurements.

Ultraviolet Irradiance over Mexico City

Abstract This article compiles and analyzes information on the interaction of both ground-level ultraviolet radiation and anthropogenic ozone in the extremely polluted atmosphere of Mexico City. Simultaneous anthropogenic ozone and global flux (sun and sky) measurements were recorded in near ultraviolet radiation (295-385 nm) for a 30-month period (March 1990 to August 1992). Results reveal that under clear sky conditions, high concentrations of ozone (and presumably of other pollutants) impede UV-fluxes from reaching their maximum values. Furthermore, heavy cloud cover causes ozone concentrations to reach their minimum values together with UV-minimum fluxes. Seasonal variation in UV-irradiance is also discussed. Findings indicate that maximum UV-fluxes occur in spring and summer and that minimum values occur in autumn and winter. Significant daily local reductions in UV-fluxes (up to 50%) during afternoon hours in Mexico City can be attributed to air pollution. Finally, the growing incidence of rickets i...

The possible influence of volcanic emissions on atmospheric aerosols in the city of Colima, Mexico

An elemental composition study of atmospheric aerosols from the City of Colima, in the Western Coast of Mexico, is presented. Samples of PM(15)-PM(2.5) and PM(2.5) were collected with Stacked Filter Units (SFU) of the Davis design, in urban and rural sites, the latter located between the City of Colima and the Volcán de Colima, an active volcano. Elemental analyses were carried out using Particle Induced X-ray Emission (PIXE). The gravimetric mass concentrations for the fine fraction were slightly higher in the urban site, while the mean concentrations in the coarse fraction were equal within the uncertainties. High Cl contents were determined in the coarse fraction, a fact also observed in emissions from the Volcán de Colima by other authors. In addition to average elemental concentrations, cluster analysis based on elemental contents was performed, with wind speed and direction data, showing that there is an industrial contributor to aerosols North of the urban area. Moreover, a contribution from the volcanic emissions was identified from the grouping of S, Cl, Cu, and Zn, elements associated to particles emitted by the Volcán de Colima.

Real‐Time AVHRR Thermal Monitoring and Ash Detection: The Case of Colima Volcano (Mexico)

In this report we examine the application of the Advanced Very High Resolution Radiometer (AVHRR) data for real-time surveillance of volcanic thermal phenomena and eruption plumes. The 14 active volcanoes of Mexico are monitored in real-time, additionally a further 18 volcanoes across Central America. This paper concentrates on the thermal monitoring and ash plume detection at Volcan de Colima, considered one of Mexicos most active volcanoes. The results reported here were selected from 296 nocturnal satellite passes acquired during 18:00 and 8:00 hours (local time). Ash clouds were detected in forty-seven (16%) passes. Frequent thermal anomalies were observed in sequential satellite passes together with ash emission. These were correlated with explosion-related waveforms apparent in seismic data. Two time periods are identified: the first period (March to May 2002) was characterized by very strong thermal anomalies with thermal pulses lasting 5 to 7 days. These anomalies were associated with incandescent pyroclastic and lava flows on the flanks of the volcano. During the second period (June to August 2002) the thermal anomalies had a much lower magnitude, with minor ash emission observed only on 19 July. During the middle of August 2002 a slight increase in the magnitude of the thermal anomalies was observed, with ash emission only on 21 August. Although there were no observations of ash fall in the city of Colima, or damage to human health, infrastructure or economic activities during this period, such real-time satellite monitoring may prove to be a very useful tool for volcano surveillance.