HR: 1340h
AN: P13A-1037    [Abstracts]
TI: Constraining Eruptive Conditions From Lava Flow Morphometry: A Case Study With Field Evidence
AU: * Bowles, Z R
EM: Zack.Bowles@asu.edu
AF: Arizona State University, P.O. Box 871404, Tempe, AZ 85287, United States
AU: Clarke, A
EM: Amanda.Clarke@asu.edu
AF: Arizona State University, P.O. Box 871404, Tempe, AZ 85287, United States
AU: Greeley, R
EM: greeley@asu.edu
AF: Arizona State University, P.O. Box 871404, Tempe, AZ 85287, United States
AB: Volcanism is widely recognized as one of the primary factors affecting the surfaces of solid planets and satellites throughout the solar system. Basaltic lava is thought to be the most common composition based on observed features typical of basaltic eruptions found on Earth. Lava flows are one of the most easily recognizable landforms on planetary surfaces and their features may provide information about eruption dynamics, lava rheology, and potential hazards. More recently, researchers have taken a multi-faceted approach to combine remote sensing, field observations and quantitative modeling to constrain volcanic activity on Earth and other planets. Here we test a number of published models, including empirically derived relationships from Mt. Etna and Kilauea, models derived from laboratory experiments, and theoretical models previously applied to remote sensing of planetary surfaces, against well-documented eruptions from the literature and field observations. We find that the Graetz (Hulme and Felder, 1977, Phil.Trans., 285, 227 - 234) method for estimating effusion rates compares favorably with published eruption data, while, on the other hand, inverting lava flow length prediction models to estimate effusion rates leads to several orders of magnitude in error. The Graetz method also better constrains eruption duration. Simple radial spreading laws predict Hawaiian lava flow lengths quite well, as do using the thickness of the lava flow front and chilled crust. There was no observed difference between results from models thought to be exclusive to aa or pahoehoe flow fields. Interpreting historic conditions should therefore follow simple relationships to observable morphologies no matter the composition or surface texture. We have applied the most robust models to understand the eruptive conditions and lava rheology of the Batamote Mountains near Ajo, AZ, an eroded shield volcano in southern Arizona. We find effusion rates on the order of 100 – 200 cubic meters per second, total volumes of 0.05 – 0.1 cubic kilometers, eruption durations on the order of days, thicknesses of 5 – 10 meters and a yield strength of 5000 Pa. These calculations are more consistent with field observations in the Batamote Mountains, which provide an order of magnitude estimate of total volume and direct measurements of flow thickness. Careful measurements of many more active lava flows should be made in order to further assess the effectiveness of predictive models, allowing the planetary science and volcanology communities to agree on an accepted methodology of interpreting paleo-eruption conditions.
DE: 5480 Volcanism (6063, 8148, 8450)
DE: 8425 Effusive volcanism
DE: 8429 Lava rheology and morphology
DE: 8450 Planetary volcanism (5480, 6063, 8148)
DE: 8486 Field relationships (1090, 3690)
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting