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Topographic and stochastic influences on pāhoehoe lava lobe emplacement

Research output: Contribution to journalJournal article

Published

Article number756
Journal publication date10/2013
JournalJournal of Volcanology and Geothermal Research
Volume75
Number of pages16
Original languageEnglish

Abstract

A detailed understanding of pāhoehoe emplacement is necessary for developing accurate models of flow field development, assessing hazards, and interpreting the significance of lava morphology on Earth and other planetary surfaces. Active pāhoehoe lobes on Kīlauea Volcano, Hawai'i, were examined on 21–26 February 2006 using oblique time series stereo-photogrammetry and differential global positioning system measurements. During this time, the local discharge rate for peripheral lava lobes was generally constant at 0.0061±0.0019 m3/s, but the areal coverage rate of the lobes exhibited a periodic increase every 4.13±0.64 min. This periodicity is attributed to the time required for the pressure within the liquid lava core to exceed the cooling-induced strength of its margins. The pāhoehoe flow advanced through a series of down-slope and cross-slope breakouts, which began as ∼0.2-m-thick units (i.e., toes) that coalesced and inflated to become approximately meter-thick lobes. The lobes were thickest above the lowest points of the initial topography and above shallow to reverse-facing slopes, defined relative to the local flow direction. The flow path was typically controlled by high-standing topography, with the zone directly adjacent to the final lobe margin having an average relief that was a few centimeters higher than the lava-inundated region. This suggests that toe-scale topography can, at least temporarily, exert strong controls on pāhoehoe flow paths by impeding
the lateral spreading of the lobe. Observed cycles of enhanced areal spreading and inflated lobe morphology are also explored using a model that considers the statistical likelihood of sequential breakouts from active flow margins and the effects of topographic barriers.