Jonathan Dehn

Chronology and complex volcanic processes during the 2002--2003 flank eruption at Stromboli volcano (Italy) reconstructed from direct observations and surveys with a handheld thermal camera

[1] Effusive activity at Stromboli is uncommon, and the 2002–2003 flank eruption gave us the opportunity to observe and analyze a number of complex volcanic processes. In particular, the use of a handheld thermal camera during the eruption allowed us to monitor the volcano even in difficult weather and operating conditions. Regular helicopter-borne surveys with the thermal camera throughout the eruption have significantly improved (1) mapping of active lava flows; (2) detection of new cracks, landslide scars, and obstructions forming within and on the flanks of active craters; (3) observation of active lava flow field features, such as location of new vents, tube systems, tumuli, and hornitos; (4) identification of active vent migration along the Sciara del Fuoco; (5) monitoring of crater’s inner morphology and maximum temperature, revealing magma level changes within the feeding conduit; and (6) detection of lava flow field endogenous growth. Additionally, a new system developed by A. J. L. Harris and others has been applied to our thermal data, allowing daily calculation of effusion rate. These observations give us new insights on the mechanisms controlling the volcanic system.

Effusive to explosive transition during the 2003 eruption of Stromboli volcano

The persistent explosive activity of Stromboli volcano (Italy) ceased in December 2002 and correlated with the onset of a seven-month-long effusive eruption on the volcano flank from new vents that opened just below the summit craters. We intensively monitored this effusive event, collecting and interpreting, in real time, an extensive multiparametric geophysical data set. The resulting data synergy allowed detailed insights into the conduit dynamics that drove the eruption and the transition back to the typical Strombolian activity. We present a direct link between gas flux, magma volume flux, and seismicity, supporting a gas driven model whereby the balance between gas flux and gas overpressure determines whether the system will support effusive or explosive activity. This insight enabled us to monitor the migration of the magma column up the conduit and to explain the onset of explosive activity.

Thermal monitoring of North Pacific volcanoes from space

Long-term thermal modeling of volcanoes using satellite imagery provides an effective tool for monitoring remote yet dangerous volcanoes in the North Pacific. This region includes volcanoes in Alaska, the Aleutian Islands, and the Kamchatkan Peninsula. Thermal infrared data collected multiple times per day from weather satellites show distinct signatures for three different types of volcanic activity at different volcanic centers. Near real-time automated techniques are being developed to monitor relative changes in radiant temperature at volcanoes in this region. Radiant temperature values as a function of time are extracted and compared to background values for a series of active volcanoes. By establishing a long-term thermal record for these volcanoes, significant deviations indicative of an impending eruption can be detected. This tool is used to search for precursors to explosive eruptions in order to increase warning times and hazard mitigation for these potentially catastrophic events. A six year archive of satellite imagery has been compiled for this active region, and is available for study.

Observations of SO2 production and transport from Bezymianny volcano, Kamchatka using the MODerate resolution Infrared Spectroradiometer (MODIS)

Bezymianny volcano, Kamchatka Peninsula, Russia, is one of the most active volcanoes in the North Pacific (NOPAC) region and erupts violently on average every 6 months. We report the SO2 cloud mass, emission and transport rates for the eruption of Bezymianny on 13–14 January 2004, and discuss the issues associated with determining SO2 production and transfer to the atmosphere from NOPAC volcanoes. During the 13–14 January 2004 eruption, Bezymianny was observed twice by the MODerate Resolution Imaging Spectroradiometer (MODIS) at 0025 and 0210 UTC on 14 January. Using a retrieval based on the 8.6 µm SO2 infrared absorption feature, MODIS yielded a total cloud mass of 34.6±5.19 kt of SO2, an SO2 emission rate of ∼(4.9×103)±(9.12×102) kg s−1, and a transport rate of ∼16.5 m s−1. We tested the sensitivity of the SO2 algorithm to the following input parameters: cloud top height, atmospheric profile, spectral emissivity of the ground and maximum SO2 threshold. The retrieval is sensitive to the atmospheric profile and is particularly dependent on the choice of background emissivity. Multiple background emissivity spectra, obtained over homogeneous backgrounds, reduce errors in the retrieval, when compared to single, less homogeneous emissivity regions.

Satellite imagery proves essential for monitoring erupting Aleutian Volcano

Mt. Cleveland is one of more than 40 active volcanoes in Alaska that is monitored by the Alaska Volcano Observatory (AVO). It is located on the western half of Chuginadak, a remote and uninhabited island in the east central Aleutians that lies 1526 km southwest of Anchorage. The closest inhabited community, Nikolski, is 75 km to the east on Umnak Island (Figure 1). Mt. Cleveland erupted explosively on 19 February and on 11 and 19 March 2001. Because the volcano is not yet monitored with seismic, deformation, or other geophysical instruments, satellite imagery was the only effective tool for detecting and monitoring this activity. Eruption clouds and elevated surface temperatures were detected on multiple satellite data sets. The largest eruption was in February. This first eruption cloud and the subsequent wave of ash (Figure 1) that drifted across Alaska extended up to flight levels and prompted cancellation and re-routing of air traffic throughout the North Pacific region on 19 and 20 February.

Volcaniclastic sediments from mid-oceanic Kolbeinsey Ridge, north of Iceland: Evidence for submarine volcanic fragmentation processes

Volcaniclastic sediments of the active Kolbeinsey Ridge, north of Iceland, reflect changing fragmentation mechanisms due to increasing sea level during the last deglaciation. Glass shards deposited on the western flank of the mid-oceanic ridge before 13.4 ka are vesicular (20%-60%), whereas shards deposited since 13.4 ka are mostly vesicle free and of hyaloclastic origin. The vesicle-rich shards display morphology thought to be atypical for submarine eruptions at this depth (400-500 m). The environmental conditions during the deposition of these layers (regional ice cover, more than 200 km from the nearest subaerial source) preclude a subaerial origin for these shards. We propose an eruption mechanism in which hot vesiculating bombs from a low-energy eruption are transported upward through the water column by convection. These particles reach their volcanic fragmentation depth (VFD) and undergo secondary fragmentation, creating the vesicle-rich shards recovered near the ridge. Rising sea level since the end of the last glaciation was sufficient to prevent the erupted particles from reaching the VFD, thus ending the formation of vesicle-rich shards. This model explains the presence of vesicular shards in sediments of mid-oceanic ridges where no subaerial source can be inferred.

Analysis of surface processes using SAR data: Westdahl Volcano, Alaska

Seasat, Earth Resource Satellite (ERS-1) and Japan Earth Resource Satellite (JERS-1) Synthetic Aperture Radar (SAR) data were used to investigate surface geomorphic and topographic changes caused by volcanic eruptions of Westdahl Volcano, Alaska. This volcano is located at the west end of Unimak Island, Alaska, approximately 1200 km southwest of Anchorage. This remote, ice-capped volcano has erupted three times in the last 34 years. The eruptions have melted portions of the ice-cap which have been replenished by winter snow. Changes in terrain were studied by comparing seasonal and inter-annual SAR data acquired over a 17 year period prior to, during and after two eruptions. The SAR data provided a record of geological and environmental processes between 1978 and 1995. Time sequential data recorded the formation of landforms and subsequent burial by snow. A series of winter images showed that changing environmental conditions, thought to be predominantly snow moisture, influence the detection and ability to analyse landforms, such as lava flows, by affecting the contrast between features and surrounding ground. Backscatter values of lava flows indicate that it would be difficult to distinguish them solely by radiometric response due to seasonal and annual fluctuations. A colour composite, formed using multi-temporal data, improved the detection of landforms and surface changes related to the eruption as well as environmental changes during the winter.

Theoretical Investigations on Potential Impacts of High-Latitude Volcanic Emissions of Heat, Aerosols and Water Vapor and their Interactions with Clouds and Precipitation

Augustine Volcano (located in the Cook Inlet of South Central Alaska at 59.4 o N and 153.4 o W) erupted in January 2006 and released, among other things, water vapor, radiation heat, and aerosols into the atmosphere. To determine the potential impact of volcanic emissions and ashfall on local weather, 16 simulations assuming artificial emission and ashfall scenarios were performed with the Weather Research and Forecasting model for 24 consecutive days starting the day before the first eruption. These simulations include (1) the control simulation without consideration of any volcanic perturbation, (2) four simulations with simplified scenarios for each individual volcanic factor (radiative heat from the caldera, water vapor, cloud condensation nuclei (CCN) and/or ice nuclei (IN) aerosols, and albedo change due to ashfall), and (3) 11 simulations containing all possible combinations of these factors. These 11 simulations serve to examine interactions among impacts of the different perturbations under the assumed scenarios. The impact of volcanic factors on local weather depends on the synoptic situation, emission strength, (combination of) volcanic factors, and interaction among impacts of factors if they occur concurrently. ANalysis Of VAriance shows that the greatest (statistically significant at the 95% or higher confidence level) volcanic impact occurs on relatively humid days and immediately downwind of the volcano (<50 km). Depending on relative humidity and temperature conditions, volcanic heat release can increase condensation and/or cloud top levels or reduce cloudiness. Due to non-linear cloud microphysical processes, meteorological responses to volcanic factors can diminish or enhance the impacts of the individual factors when factors occur concurrently. As an example, depending on the ambient conditions, concurrently occurring volcanic factors can lead to a decrease in precipitation at one time and an increase at another time. These findings indicate that in the immediate vicinity of erupting volcanoes, predicted cloud conditions and precipitation may be inaccurate due to the unknown volcanic forcing.

Volcanic Materials in Commerce and Industry

Abstract The products of volcanic eruptions have provided useful raw materials for man throughout history. In many regions of the world volcanic rock is ubiquitous, and the inhabitants of these regions have developed ingenious uses for this natural resource. Ranging from early weapons and implements to building materials, volcanic rocks have been sought out because of their physical properties for use in manufacturing processes, as insulators, absorbents , or abrasives. Volcanic materials play an important role in our lives, regardless of whether or not we live near volcanoes, although most of us do not realize their wide variety and applications.

A near real-time dual-band-spatial approach to determine the source of increased radiance from closely spaced active volcanoes in coarse resolution satellite data

Bezymianny and Kliuchevskoi volcanoes (Kamchatka) present a danger as both inject ash into North Pacific air routes. Current automated monitoring algorithms do not distinguish them in real time due to their mutual proximity (10 km) and poor geolocation accuracy of Advanced Very High Resolution Radiometer (AVHRR) data. Contrasting mid- and thermal infrared volcanic radiances are influenced by (1) differences in temperature and eruptive style of Bezymiannys andesite and Kliuchevskois basalt and (2) different temperatures of the non-volcanic portion of pixels located over their summits, due to different elevations. Data from 571 AVHRR images show the latter is more significant. Discriminant function analysis using summit and regional band 4 pixel-integrated radiant temperatures (pirT) correctly identifies the source volcano of a thermal anomaly in 89% of cases. Weather permitting, a spatial component can be added, leading to improved accuracy. The approach used here can also be applied at other closely spaced volcanoes with substantially different summit elevations.