61-5 Recreational Drones as Tools for Remote Geologic Mapping: Case Studies from the Tieton Andesite and Devils Horn Rhyolite

Session: Advancing Geologic Analysis with Digital Outcrops and Close-Range Remote Sensing Data (Posters)

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Remote terrains with high cliffs, thick vegetation and unstable talus slopes often conceal critical geologic features that remain unexplored due to hazardous access; drones offer a new way to bridge that gap. This project demonstrates how recreational, and affordable drones can be used to analyze unreachable outcrops and identify new ones without the need for ground-based searches, using the Tieton Andesite, and Devils Horn Rhyolite (Tpr) as case studies. The Tieton Andesite lava flows of Bear Creek Mountain are two of the longest flows in the world, with lengths of 74 and 52km. They erupted from Goat Rocks volcanic complex in the south-central Washington Cascades, driven by subduction of the Juan de Fuca Plate beneath the North American Plate. The longer flow (Qta1) has a 39Ar/40Ar date of 1.64 ± 0.04 Ma, and the shorter flow (Qta2) has a date of 1.39 ± 0.10 Ma. By comparison, the Devils Horn Rhyolites (Tpr) represent a substantial sequence of high-silica rhyolitic deposits dating to the upper Pliocene, with an estimated zircon fission-track age of ~3.2 Ma (Clayton, 1983). These rhyolitic units, reported at up to 650 meters thick, unconformably overlie the Rimrock Lake Inlier beneath both Bear Creek Mountain and the Devils Horn. Much of the Tieton Andesite lava flows and Devils Horn Rhyolites has been mapped, but several inaccessible outcrops remain unexamined due to hazardous terrain. To address this, a DJI Air 3s drone was deployed to capture footage of remote outcrops, revealing previously undocumented morphological features. Stratigraphic columns were constructed from drone imagery using ImgJ and Pixelmator Pro, and simplified outcrop sketches were produced to highlight key geologic structures. The drone also aided in locating new outcrops of Qta2, Tpr, and a basaltic andesite unit linked to the Bear Creek eruptive stage. This study highlights the practical value of recreational drones in geologic fieldwork, particularly for mapping, stratigraphic analysis, and reconnaissance in areas that are otherwise unsafe or inaccessible by foot.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-10739

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