V41A-01
Recent Developments in Monitoring of Gas and Ash in Volcanic Plumes by Remote Sensing Techniques
Since the 1970s, a growing list of methods for the remote detection and measurement of the composition and dynamics of volcanic plumes has been available for volcanologists and atmospheric scientists. During the last decade of intensive volcanic activity in Ecuador, the use of spectroscopic techniques like COSPEC, DOAS or FTIR has become an important tool in routine volcano monitoring which has resulted in a better understanding of source and path processes related to volcanogenic gas and ash emissions with increasing spatial-temporal resolution capabilities. The most important developments achieved with these techniques include the incorporation of radiative transfer and diffusion modelling in automatic data processing routines. In addition, work is being done to identify and quantitatively estimate the presence of ash by means of UV spectroscopy. The use of these methods allowed us to follow the degassing process of Tungurahua volcano with unprecedented detail. A brief description of these improvements and their results are presented.
V41A-02
NOVAC Scanning Instruments at San Cristóbal and Masaya Volcanoes (Nicaragua): Installation and First Results
Volcanic emissions monitoring during volcanic unrest, especially at eruptive and intense passive degassing stages can give good indication of the pattern of activity of a volcano. The Network for Observation of Volcanic and Atmospheric Change (NOVAC) project encompasses a global network of stations to monitor volcanic gas emissions using Scanning Dual-beam miniature - Differential Optical Absorption Spectrometer (Mini-DOAS) instruments. This paper describes the installation of Scanning-DOAS instruments at San Cristóbal and Masaya volcanoes, as part of the NOVAC project. San Cristóbal and Masaya volcanoes form part of the Central American volcanic arc and both present permanent degassing conditions. In November 2006, three Scanning-DOAS instruments were installed at San Cristóbal volcano. The instruments scan over a 180° vertical plane, traversing the plume downwind the source and were placed perpendicularly to the predominant plume propagation direction. Additionally two Scanning-DOAS instruments were installed in the caldera of Masaya volcano during April 2007. A detailed description of the installation of Scanning-DOAS instruments at San Cristóbal and Masaya volcanoes and first results are further discussed.
V41A-03
SO2-emission Monitoring Network of Popocatépetl Volcano (Mexico): Installation and First Results of NOVAC Scanning Instruments
Popocatépetl volcano 60 km SE of Mexico City is a high-emission rate, passively degassing eruptive stratovolcano. On December 21 1994, Popocatépetl started to erupt and the activity has continued, consisting of degassing, explosions, ash emissions and lava, as well as the recurrent dome formation and destruction by explosions of variable energy magnitude as well as seismicity. Popocatépetl forms part of the Network for Observation of Volcanic and Atmospheric Change (NOVAC). The NOVAC project encompasses a global network of stations to monitor volcanic gas emissions using Scanning Dual-beam miniature - Differential Optical Absorption Spectrometer (Mini-DOAS) instruments. This report describes the installation, at Popocatépetl volcano, of three Scanning Dual-beam DOAS instruments as part of the NOVAC project. Details of the installation, selection of suitable sites and data transfer are further discussed. First results from the instruments are also presented, and particularly the usefulness of this array.
V41A-04
Anomalous Soil Temperature and CO2 Emissions at Cerro Pacho (Coatepeque Caldera) and Santa Ana Volcano before the October 1, 2005 Eruption of Santa Ana Volcano
Coatepeque Caldera and Santa Ana Volcano belong to the Santa Ana-Izalco-Coatepeque volcanic complex in western El Salvador. The last eruption of Santa Ana Volcano on October 1, 2005 killed two people and damaged 65% of the cultivated land around the volcano due to ash emissions and gases. Prior and after the eruption, we carry out several CO2 soil efflux and soil temperature surveys of Cerro Pacho fumarolic field and Santa Ana Volcano crater. For the diffuse CO2 emission, at Cerro Pacho the total CO2 efflux emited to the atmosphere from an area of 2600 m2 on April 1, September 7, and October 26, 2005, was 77, 99 and 64 kg/day respectively. In comparison, at the south-east perimeter of Santa Ana Crater, CO2 emissions on September 2 and September 21, 2005, were 112 and 442 g/m2 day, respectively (Barahona et al.,2007,this meeting). These values are one order of magnitude higher than the 15 g/m2 day measured in the same region by Salazar et al. (2004). For the soil temperatures at Cerro Pacho and at the south of Santa Ana crater, three areas of temperatures higher than 60°C were identified. According to Allis (1979), for soil temperatures lower than 60°C the dominant heat transport mechanism is conductive, there is a transition zone between 60-70°C, and the convective zone occurs at temperatures higher than 70°C up to the boiling point. At Santa Ana crater and at Cerro Pacho, the temperature anomalies were oriented in the NW-SE and E-W direction. In Santa Ana crater, the conductive zone was more important with a 49.1% of the surveyed area on May 8, and a 57% on April 7, 2005. This increase in convective heat flow suggest an increase in thermal heat from the volcano. At Cerro Pacho we have only a slight difference of 90 to 92% in the conductive area during April 3 and October 26, 2005, respectively. The increase in diffuse soil CO2 and the variations in the thermal field at the Santa Ana Crater and the Cerro Pacho fumarolic field can be interpreted as premonitory signals of the Santa Ana Volcano eruption. At other active volcanoes, monitoring of the soil temperature and diffuse emissions of gases could be important methods to follow the state of activity of a volcano.
V41A-05
Effect of the ash Fall on the Human Health at Colima Volcano During 2005-2006.
Colima Volcano in western Mexico had several small ash emitting eruptions during 2005-2006. In this time period we studied the impact of the ash fall on human health through field observations, interviews and health data processing. The volcano was most active in May-June 2005. Data from 15.000 medical records of the Colima and Jalisco State Health Departments show two main health problems in humans during this time: Conjunctivitis was detected in 1,933 people and respiratory disease in 12,630 people in an area of 1,841,283 km2 which was affected by small amounts of ash fall near the volcano in 2005. Ash emissions from Colima Volcano correlate well with increased affections. When emissions increased so did the frequency of these health problems in the population.
V41A-06
Pre and Post-Eruptive Variations in Diffuse Soil CO2 Degassing at the Crater Rim of Santa Ana Volcano, El Salvador, Central America
Santa Ana volcano, in western El Salvador, Central America, erupted on October 1st, 2005. Before and after the eruption, this volcano has been monitored seismically, with measurements of diffuse fluxes of soil gases and measurements of SO2 emissions in the volcanic plume. In 2001, a survey of diffuse soil CO2 around the crater found only very low or non-detectable values of diffuse soil CO2 (Salazar. et., al 2001). After signs of in this volcano, a profile of diffuse emissions of CO2 around a portion of the crater rim was monitored. This profile covers an arc of 65 m along the SE of the crater, in a zone that did not show emissions of CO2 in 2001. 13 observation points were selected for this discrete monitoring in seven different dates, three before and four after the eruption. The measurements were done using the accumulation chamber method (Chiodini.,et al, 1998) and an infrared spectrometer Licor LI-820. The results show that the average, maximum, and minimum fluxes for the entire profile increased around one order of magnitude for the period between August 31st and September 21, 2005, with highest measured values in September 21st. The mean, maximum and minimum values were 442, 1439 and 5 g/m2d, respectively, on that day. The mean, maximum and minimum fluxes presented the lowest values in February 28, 2006, with values of 8 g/m2d for the mean, 40 g/m2d for the maximum and non-detectable for the minimum. After February 28, the flux of CO2 has presented only small. These observations show that Santa Ana is in a period of minimum emission of diffuse gases due to a relatively low activity as compared with the August-September, 2005 activity. This work shows how important it is to monitor the diffuse soil gases in discrete mode for the detection of early signals of volcanic reactivation. This observations together with seismic monitoring and the monitoring of plume gases seem to be a promising methodology for the forecast of volcanic eruptions.
V41A-07
A Direct Comparison of MODIS and COSPEC Sulfur Dioxide Measurements of the May 21, 2003 Eruption Plume of Anatahan Volcano, Mariana Islands
Quantifying the SO2 burden emitted from a volcano is critical to understanding a volcano's current state of activity. Ground-based instruments such as the correlation spectrometer (COSPEC) and the mini-DOAS are most routinely employed to measure volcanic SO2. Both instruments are human operated so they must be deployed on-site to obtain SO2 estimates. This makes it difficult and costly to regularly monitor active volcanoes world- wide. Satellite-based measurements, which can provide SO2 estimates in near real-time, have increasingly been used as a tool for volcanic monitoring. The Moderate Resolution Imaging Spectrometer (MODIS) located on board the Terra and Aqua satellites provides twice daily coverage of the Earth and has the capacity to detect volcanic SO2. The ability of MODIS to accurately detect and quantify SO2 in volcanic plumes using a SO2 retrieval program, MAP_SO2, was compared with COSPEC on the May 21, 2003 plume at Anatahan volcano (16.35oN, 145.67oE). MODIS was able to clearly detect SO2 in the plume and the MAP_SO2 derived SO2 flux was calculated (independently from the COSPEC data) to be more than twice the COSPEC derived flux (10,270 t/d and 3,000 - 4,500 t/d respectively). However, calculating a flux introduces additional errors. Therefore another means of comparing the two methods is utilized: a direct comparison of plume cross-sections from these two different methods. The MODIS image used with the MAP_SO2 program was acquired at 13:25 local time. The COSPEC traverse began at 13:35 local time and ended 14:40 local time. The time of the MODIS image acquisition and the start of the COSPEC traverse occurred within 10 minutes of each other. Although the MODIS image is a snap shot in time and the COSPEC traverse took about an hour to complete, the timing is so close that these two products are ideal for the comparison. The differences in these observations are used to better quantify SO2 emissions, to assess the current mismatch between ground-based and remotely sensed retrievals, and to aid in the development of an approach to continuously and accurately monitor volcanic activity from space in near real-time.
V41A-08
Collaborative Monitoring and Hazard Mitigation at Fuego Volcano, Guatemala
A portable, digital sensor network has been installed to closely monitor changing activity at Fuego volcano, which takes advantage of an international collaborative effort among Guatemala, U.S. and Canadian universities, and the Peace Corps. The goal of this effort is to improve the understanding shallow internal processes, and consequently to more effectively mitigate volcanic hazards. Fuego volcano has had more than 60 historical eruptions and nearly-continuous activity make it an ideal laboratory to study volcanic processes. Close monitoring is needed to identify base-line activity, and rapidly identify and disseminate changes in the activity which might threaten nearby communities. The sensor network is comprised of a miniature DOAS ultraviolet spectrometer fitted with a system for automated plume scans, a digital video camera, and two seismo-acoustic stations and portable dataloggers. These sensors are on loan from scientists who visited Fuego during short field seasons and donated use of their sensors to a resident Peace Corps Masters International student from Michigan Technological University for extended data collection. The sensor network is based around the local volcano observatory maintained by Instituto National de Sismologia, Vulcanologia, Metrologia e Hidrologia (INSIVUMEH). INSIVUMEH provides local support and historical knowledge of Fuego activity as well as a secure location for storage of scientific equipment, data processing, and charging of the batteries that power the sensors. The complete sensor network came online in mid-February 2007 and here we present preliminary results from concurrent gas, seismic, and acoustic monitoring of activity from Fuego volcano.
V41A-09
SO2 Monitoring of Popocatépetl Volcano (Mexico) Using MODIS (November 2006-February 2007): Comparison and Coupling with COSPEC and Seismic Data
Popocatépetl volcano in Mexico (19.020N, 98.620W, 5425 masl) has been erupting since December 1994. Since March 1996 the eruption style has been characterized by alternating explosive and effusive activity, accompanied by high-volume emissions of SO2. For more than a decade, the degassing has been documented with COSPEC and, more recently, a scanning mini-DOAS system. We complement our field-based surveys with satellite-based remote sensing, deriving maps of SO2 and ash clouds from MODIS imagery. Here we present MODIS-based SO2 retrievals for the period November 2006 - February 2007, compare these results with our COSPEC and DOAS measurements,and discuss the joint interpretation of the gas emission and seismic records for this period. Starting in 2005, there has been an increase in activity represented by the frequency and magnitude of micro- seismicity as well as emissions of gases and ash to the atmosphere. Measurements showed that SO2 emission rates show a high variation, especially in order-of-magnitude changes. Data obtained from MODIS images permit to characterize periods with peaks up to 40000 t/d by November 2006. Also, it is observed that the SO2 emission maintains their magnitude after December 20, 2006 when light emissions of ash occurred. At this time a lava dome was growing inside the crater of the volcano and continued up to January. In November, January and February tremor episodes have been occurring and a destruction of the dome produced by an explosive event is likely. The analysis and interpretation of the data help to forecast important eruptive events.