HR: 1330h
AN: V42B-0368    [PDF]
TI: Spatial Analysis of the Landbrotsholar Rootless Cone Group, South-Central Iceland: Preliminary Results
AU: * Bruno, B C
EM: bruno@alumni.brown.edu
AF: University of Hawaii, HIGP, 1680 East-West Road, POST 602, Honolulu, HI 96822 United States
AU: Fagents, S A
EM: fagents@hawaii.edu
AF: University of Hawaii, HIGP, 1680 East-West Road, POST 602, Honolulu, HI 96822 United States
AU: Thordarson, T
AF: University of Hawaii, HIGP, 1680 East-West Road, POST 602, Honolulu, HI 96822 United States
AU: Baloga, S M
AF: Proxemy Research, 14300 Gallant Fox Lane, Bowie, MD 20715 United States
AU: Harvey, R
AF: University of East Anglia, School of Computing Sciences, Norwich, NR4 7TJ United Kingdom
AB: Here, we examine the spatial distribution of the Landbrotsholar rootless cone group in South-Central Iceland. Rootless cones (or pseudo-craters) are hydrovolcanic cones of spatter and scoria that rest directly on tube-fed pahoehoe lava flows. They are formed by explosive interaction between the host lava and underlying water-saturated sediments; they do not represent primary volcanic constructs. Within a given rootless cone group, cones generally appear to be randomly distributed, lacking any obvious association with linear features such as eruptive fissures. However, in the Landbrotsholar group, some cones appear to be linearly aligned. The significance of this apparent alignment is unclear, but it might be related to sequential eruptions along preferred internal pathways (e.g., lava tubes) within the flow field and/or changes in the water content and density of the waterlogged substrate. The spatial distribution of rootless cones may therefore have important implications for the dynamics of these hydrovolcanic explosions and the mechanisms of cone formation. We employ various spatial analysis techniques to examine the Landbrotsholar rootless cone group in detail, including both global and local techniques. These methods provide a means for assessing the degrees of spatial randomness in the cone field and evaluating the statistical confidence in this assessment. Our work entails: (1) developing a filter to automatically identify rootless cones from digital images; (2) identifying spatial trends (such as linear alignments) within the cone group by applying a Hough Transform and identifying peaks in the transformed image; (3) quantifying the characteristic spacing among cones using nearest-neighbor analyses; and (4) relating these results to the underlying processes governing cone formation. Specifically, we aim to elucidate the relative roles of lava tube distribution and substrate hydrology in determining rootless cone distribution. This work may also lead to the development of a remote sensing tool to differentiate rootless cone groups from primary cone groups in digital images.
DE: 8414 Eruption mechanisms
DE: 8494 Instruments and techniques
DE: 8499 General or miscellaneous
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting