Vent Morphology at the Holuhraun Lava Flow (Northern Iceland) as an analog for martian fissure vents

Abstract:

Elongate volcanic vents are a common feature in volcanic fields on the Moon, Mars, and Earth and are generally the source for basaltic lava flows. On Mars, hundreds of these elongate fissure vents have constructed the current landscape within the Tharsis Volcanic Province. The fissure vent system of the Holuhraun lava flow in central Iceland has an analogous morphology to the fissure vents in Tharsis. In addition to a large lava flow field, the main phase of this eruption (August 31, 2014 to February 27, 2015) constructed several pyroclastic cones, the largest of which is Baugur, a 500-m long, 50-m deep spatter rampart. The exterior of Baugur exhibits multiple lava channels that fed the Holuhraun lava flow, and its main flanks are built by basalt pyroclasts that are variably welded. The interior of Baugur hosts cliff faces that expose welded spatter and sub-horizontal ledges made of basalt lava.

Volcanic materials at Baugur were described by our team during field expeditions to the region between 2015–2019. Terrestrial lidar surveys were performed within the main Holuhraun vent and its proximal channel using a Riegl VZ-400 laser scanner. Stereophotogrammetric surveys were completed with a Trimble UX5 HP fixed wing drone with a 36 MP full-frame digital camera. These surveys produced DEMs at 12–20 cm/px and orthoimages at 2.5–4 cm/px. Videos and images during the 2014–2015 eruption from tourists, park rangers, and scientists, as well as material provided by the Icelandic meteorological office in monthly reports enabled the production of a timeline of eruptive activity at the vent.

Similarities between martian fissure vents and the Baugur vent can enable the interpretation of their volcanic eruptions. The presence of many small channels at volcanic vents is similar to the early period of construction at Baugur when isolated fire fountains along the fissure each produced channels. The presence of a main channel and buried channels suggests a sustained eruption lasting weeks or more instead of a single outburst of lava. Morphologic differences between Holuhraun and martian vents indicates differences in eruption dynamics on Mars. Raised rims on martian vents, for example are generally much thinner than the vent width, implying that a smaller amount of fountained lava was able to weld together upon deposition.