Ashley K. Hatfield

Historical eruptions of Mt. Etna spanning the time from A.D. 1600 to present often produced lava flows. Low-altitude flank eruptions tend to be the most hazardous because these eruptions can potentially reach vulnerable areas. The use of geographical information based software permits the quick quantification of lava flow hazards while simultaneously representing the data graphically. Additionally, understanding volcanic processes greatly aids in the characterization of such volcanic hazards. Important parameters include the tectonic and geologic environment, the supply and storage of magma in a reservoir, the mechanism for magma supply to the surface, and the stability of the volcanic structure. Post-1600 eruption data, including the frequency of lava flow invasion and the distribution of vents, as well as the morphology of the volcano and the physical parameters of lava flows, were utilized for the production of a hazard zonation map. A vulnerable region covering an area of 1400 km2 was defined and subdivided on the basis of whether the region was largely populated, industrial or agricultural. This research is important because no historical precedent exists for a city being invaded by a lava flow.

The isotopic composition of helium and the chemical composition of gases released from fumaroles on the island of Vulcano indicate that a magma reservoir lies beneath the island. A Geographic Information System was utilized to correlate spatial relationships to measured geochemical parameters. The maps generated clearly reveal an increase in out-gassing activity in the crater, as well as a shift toward the inside flank of the crater, occurred from 1985 to 1995. This observation highlights the important role(s) that tectonics and volcanic activity plays in fumarolic output.

Simple lava flows, often characterized by aa textures, have single lobes, whereas compound lava flows, characterized by pahoehoe textures, have interfingering lobes. The emplacement type of compound lava flows are hypothesized to depend upon factors such as the localized topographic relief and the presence or absence of lava tubes. Four main classes of pahoehoe lava flows, as determined by their dominant morphologic features, were identified and mapped on aerial photographs. GIS-based analysis reveals that a crude relationship exists between lava flow emplacement and topography, but lava tube segment location produces little to no effect on the emplacement of compound lava flows. Further research could incorporate additional lava unit types, such as flows characteristic of vent regions, as well as incorporate additional datasets, such as thermal and radar remote sensing, to better characterize the flow fields.

The city of Quito is spatially positioned at the base of the Pichincha volcano complex in such a manner that it is at high risk for inundation by lahars, or debris flows of volcanic origin. Lahar modeling was carried out for the two major valleys where the largest and most hazardous lahars form. Two different GIS-based models analyzed the data for the purpose of results comparison. LAHARZ produced straight, elongated deposits, and FLO-2D produced deposits that spread out over a large area of the fan surface. Neither model completely reproduced the shape of past lahar deposits. This may be due to the modification of the drainage by human activity. Nonetheless, each model may hold a place in hazard management: LAHARZ can rapidly provide information about which regions are most likely to become inundated during emergencies, whereas FLO-2D is best utilized for middle and long-term hazard management due to the large amount of fieldwork necessary prior to running the model.

The simultaneous analysis of vegetative distribution and landforms, or phyto-geomorphology, provides insight into regions of past geologic processes, such as volcanic activity and glacial phenomena, and present-day stresses to the environment. This type of analysis is best carried out with the aid of a geographic information system because GIS can manage large databases, and link geospatial data to attribute data. The north slopes of Ajusco volcano exhibit the features indicative of past glacial cirques and moraines, while the south slopes exhibit features indicative of periglacial processes, such as cryoclasticism. These factors, as well as environmental factors such as humidity and elevation, produce a noticeable difference in vegetative cover on the volcano, as the northern slopes contain fir forests while the south slopes harbor pine-grassland communities.

Magma eruption rates for the Ceboruco-San Pedro volcanic field, western Mexico, are calculated on the basis of ⁴⁰Ar/³⁹Ar geochronology and volume calculations of volcanic units. Field mapping is supported by the use of GIS for digitizing topographic features and the subsequent calculation of unit volumes. The relative proportion of erupted lava tied to its position in the eruptive sequence provides a time-progressive pattern for magma composition. Major element geochemistry is used to divide samples on the basis of SiO₂ content, and trace element geochemistry (La, Zr vs. SiO₂) is used to model the geochemical diversity of the erupted lavas over time. After determining the relative proportions of lava types erupted over the past 1 Ma, it is clear that intermediate magma compositions dominate. Diverse geochemical signatures of the lava types indicate that lava flows originated from numerous parental liquids, rather than from a single crystal-fractionated parent liquid. Thus, first-order differentiation processes of arc magmas at subduction zones likely occur within the lower crust, not in long-lived magma chambers within the upper crust.

The hazards posed by lava flows include fire, isolation from utilities, access isolation, and coverage of a region. This hazard is quantitatively assessed on Mauna Loa volcano through the use of Geographic Information System software. Previous estimates of lava flow hazards in Hawaii were dominantly qualitative in their approach, and ranked hazard potential from highest to lowest. In this study, field-based geologic maps were converted to vector format and analyzed with ArcInfo. Flows within a certain distance of a target region were tabulated on the basis of their age, morphology, and mineralogy. Subsequently, both the probability of lava flow occurrence and coverage were calculated with appropriate algorithms, and contour maps of hazard probability were generated for the target region polygons.

The analysis of satellite data representing the visible reflected radiance field of basaltic lava flows from Mauna Loa, Hawaii, and Mount Etna, Italy, demonstrates that volcanic reflectance fields are scaling in nature, and that variation in radiance intensity is a function of spatial resolution. This resolution dependence must be solved in order to produce better, quantitatively accurate hazard maps, and to develop dynamic eruptive models for volcanoes. Combining remotely sensed data with other data types in GIS algorithms may represent one way in which to better study volcanoes, such as through the characterization of the universal multi-fractal and anisotropic properties of surfaces found on a volcano.

Quaternary-aged sequential collapse of the north flank and summit region of Bejenado volcano on La Palma, Canary Islands, may be the source for volcaniclastic fan delta deposits and toreva remnants occupying the central part of the Caldera de Taburiente. The collapse of Bejenado volcano is due in part to its initial formation upon unstable volcaniclastic substratum. Analysis of the spatial and temporal relationship between the formation of the volcaniclastic deposits and the destruction of the volcano is carried out with GIS. Specifically, GIS was used to analyze the dimensional data and calculate volumes.

Volcanic ash poses a threat to normal aircraft function in terms of reduced visibility and the potential for engine malfunction. Additionally, ash causes the abrasion of airplane parts and the clogging of important passageways. Thus, airlines would greatly benefit from understanding the geographic relationship between airplane flight paths and the locations of volcanoes likely to produce ash plumes. GIS-based predictive models and real-time warning systems aid in making real-time flight path decisions when trying to avoid ash plumes. However, determining flight-path vulnerability prior to an eruption could greatly reduce the economic burden placed on airlines for re-routing and grounding airplanes affected by an ash plume.

Indices for determining flight-path vulnerability include wind direction, distance to the volcano, and flight-path attributes. These components are used to determine the relative vulnerability of various flight paths to ash plumes, measured in terms of their vulnerability index (FVI) and average flight path vulnerability index (AFVI). Calculating these indices is made easier with GIS. In consequence, the hazard that a particular volcano presents to a given airline can be determined.

The Western North American Volcanic and Intrusive Rock Database (NAVDAT) serves as a chemical and age data repository for igneous rock data generated over the past 30 years for western North American igneous activity. Integration of these data provides new insight into the tectonic evolution of the continent. NAVDAT aims to provide researchers with easy access to the compiled datasets with the additional ability to query on the basis of age, composition, or geographic position. More sophisticated analysis capabilities include the ability to assess the relationship between volcanism and factors such as the orientation of the subducting slab, the role of mantle plumes in the development of the continent, and the transition from continental to ocean-like mantle in the Basin and Range. This data tool contributes greatly to the overall geoscience cyberinfrastructure and is available online at http://navdat.geo.ku.edu and http://navdat.geongrid.org.