IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

0P1_3H-O3

Room A5

Date/Time: July 20 15:00-15:15

Topographic and stochastic influences on pāhoehoe lava lobe emplacement
Christopher W Hamilton1 , Lori S Glaze1 , Mike R James2 , Stephen M Baloga3
1Planetary Geodynamics Laboratory, NASA Goddard Space Flight Center, USA, 2 Lancaster
Environment Centre, Lancaster University, UK, 3 Proxemy Research, Laytonsville, USA
E-mail: christopher.hamilton@nasa.gov

Basalt is the most common rock type on the surface of terrestrial bodies throughout the Solar System and—by total
volume and areal coverage—pāhoehoe flows are the most abundant form of basaltic lava on Earth. Models of flow
field development are important for understanding the hazards imposed by terrestrial lava flows and for interpretingthe significance of lava morphologies on Earth and other planetary surfaces. However, at present, such models arelimited by the availability of dynamic dimensional measurements of active flows and the characterization of random
influences on flow emplacement. This study addresses this issue by characterizing topographic and stochastic
influences on active pāhoehoe lobes from Pu‘u ‘Ō‘ō on Kīlauea, Hawai‘i, during 21–26 February 2006 using obliquetime-lapse stereo-photogrammetry and differential global positioning system (DGPS) measurements. At this time,
the local discharge rate supplying lava to a distal lobe was 0.0061 ±0.0019 m3 /s. This rate was generally constantduring the period of observation, but every 4.13 ±0.64 minutes there was a 2- to 6-fold increase in the areal
coverage rate. This periodicity is attributed to the time required for the pressure within the liquid lava core toexceed the cooling-induced strength of its margins. The pāhoehoe flow advanced through a series of down-slopeand 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 byhigh-standing topography, with the zone directly adjacent to the final lobe margin having an average relief that wasa few centimeters higher than the lava-inundated region. This suggests that microtopography (i.e., cm-scale relief)
can exert strong controls on pāhoehoe flow paths by impeding peripheral toes and confining the interior portionsof flow. This study also develops models to explore the effects of random and correlated growth processes during
the emplacement of pāhoehoe lobes. Results show that cycles of enhanced areal spreading and inflation can be
reproduced by simulating the preferential growth of lava lobes in the direction of new breakouts using a probability
distribution that governs the possibility of the correlated emplacement of lava parcels from the flow margins. These
examples demonstrate the value of time-series observations of active pāhoehoe emplacement processes. It further
clarifies the need for future observations of dynamic topography coupled with surface temperature distributions todetermine how thermo-rheological parameters affect the location and frequency of new breakouts as well as thebalance between areal spreading and inflation.

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