CHARACTERIZING LAVA FLOW BEHAVIOR USING DIGITAL MODELS OF SMALL TUBES FROM 1961 PAHOEHOE FLOWS FROM ASKJA, ICELAND

Vikrahraun, a 1961 eruption at Askja Volcano, Iceland, produced a series of alternating a’a and pahoehoe lava flows from multiple clustered vents over seven weeks. To constrain the relative contribution of lava tubes in the pahoehoe flows, a field campaign identified and measured lava tubes and collapse features. Satellite image-based mapping then supported field observations of the distribution and relationship between tubes, ponds, and bifurcations. Three small (2 m diameter) lava tubes and two (>2 m diameter) collapse features were digitized using a low-cost photogrammetry technique that relies on a local coordinate system to compensate for the challenge of collecting accurate GPS coordinates in underground environments. Supporting field measurements of crustal thickness and opening geometries were collected to help validate the three-dimensional models. The lava tube features ranged from 200-250 centimeters in interior floor width and 60-100 centimeters in cavity height. The crust thickness of lava tube MT009 was 27 centimeters with a width of >200 centimeters and a height of 100 centimeters in the field which were reflected in the digital model with an average percent error of <11%. The longest recorded lava tube had an organized length of 111 meters (measured using satellite imagery) and an average interior height of 2.6 meters (measured in the field). 50% of the encountered lava tubes had branches of subsequent tubes off the central cavity. We also identified five lava ponding areas, two of which had numerous tubes extending from the pond margin. These data are used to better understand how lava was distributed during the 1961 eruption at Askja. The digital three-dimensional models generated can also be used for more detailed analysis of internal flow dynamics. This type of detailed analysis of lava flow features highlights the complexity of flow fields which is important to numerical simulations and the remote analysis of lava flows on Earth and other planetary bodies.