Investigations of Lava Flows in the Pinacate Volcanic Field as Analogues for Mars

Category: Cover Story

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For a NASA project that includes comparative studies of volcanic features on Earth and Mars, a team of PSI researchers and colleagues recently conducted investigations in the Pinacate Volcanic Field (Sonora, Mexico). The researchers studied the Ives Flow, a ~13,000 year old basaltic lava flow field that extends for 15 kilometers between the granitic Sierra Blanca and the Gran Desierto.

Terrestrial analog studies in Mexico, and in several regions of the western U.S., focus on documenting morphologic and topographic characteristics at volcanic contacts, where lava flows border and have flowed against pre-existing terrain. Studies of volcanic contacts on Earth are being used to inform interpretations of flow emplacement and local stratigraphic relationships on Mars. With high-resolution orbital datasets and increasingly sophisticated exploration of the Martian surface, geologic assessments of volcanic contacts provide robust interpretations of geologic processes and context for samples and surface analyses. Terrestrial analogs are critical for documenting diversity of contact types, primary morphologies at contacts, and signatures of degradation that occur with various forms of geologic activity over time.

Research activities at the Ives Flow included field examination of flow properties and acquisition of low-altitude UAS (uncrewed aerial system, or drone) images. Imaging surveys allow detailed characterization of the different types of flow margins observed. Stereo images (resolution ≤ 5 cm/pixel) are being using to construct high-resolution Digital Terrain Models (≤ 10 cm/pixel) from stereophotogrammetry. Study sites included locations where a) lava flowed against and into alcoves at the base of Sierra Blanca, b) lava flowed unconfined across relatively flat surfaces adjacent to the Gran Desierto, and c) Gran Desierto sands have partially buried flow margins.

The Ives Flow exhibits well-preserved pahoehoe (Hawaiian term) textures, including smooth, ropy, striated, rubbly, and knobby surfaces, and shows abundant evidence for flow inflation in the form of sinuous ridges, tumuli (inflation mounds), and plateaus with prominent inflation cracks. Numerous circular to irregular lava-rise (or inflation) pits are also observed and give the flow field surface an uneven, discontinuous appearance. Inflation, common in pahoehoe lava flows on Earth, occurs as parts of the flow surface are uplifted due to subsurface injection of lava. Inflation occurs in the Ives Flow at various scales, with both local uplift (within flow lobes and forming tumuli) and broad uplift forming plateaus commonly with relief of 5 meters or more.

The research was supported by NASA’s Solar System Workings Program. The research team included PSI scientists David A. Crown (project lead), Frank C. Chuang, and Stephen P. Scheidt (also at University of Maryland) along with Steven W. Ruff (Arizona State University) and Francisco Zamora (Sonoran Institute). Logistical support was provided by Daniel Zamora Miranda at El Pinacate y Gran Desierto de Altar Biosphere Reserve.

Perspective view of lava flow margin. Oblique view of UAS (uncrewed aerial system) orthophoto merged with DTM derived from stereophotogrammetry. At right, plateau formed by inflation of the once sheet-like flow surface is relatively flat with large, ropy surfaced polygons formed by cooling fractures and accentuated by the accumulation of sand in local topographic lows. At center and to left, inflated lobes of pahoehoe extend from the inflation plateau. Note marginal crack on inflation plateau and medial cracks in lobes. Lava-rise pit at top (center) is ~30 meters across. Credit: Stephen Scheidt/PSI.

Pahoehoe lava flow field in the southeastern part of the Pinacate Volcanic Field (Sonora, Mexico) with the Sierra Blanca range in the background. Note ropy lava surface in foreground and sand-covered depression at the base of inflated lava (with large cracks) in mid-ground. Credit: David Crown/PSI.