18-7 Devil's Garden Lava Flow Field, Oregon: A Planetary Analog

Session: Surface Processes Across the Solar System

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Abstract:

Devil’s Garden lava flow field (43°30’N, 120°56’W) is a complex basaltic system that displays multiple vents and pseudovents, and displays a range of morphologies that make it a strong planetary analog.

The flow-field comprises ~1.2 km³ and is named for a vegetated kipuka that covers ~25 km².  Devil’s Garden lavas have not yet been age-dated, but they underlie pumice from the cataclysmic eruption of Mount Mazama (~7700 years ago) and rest on top of Holocene-aged rocks. A Pleistocene pluvial lake, known as Lake Fort Rock, occupied Fort Rock Valley (southwest of Devils Garden) until ~10 – 16 Kyr ago.

Unlike lavas near the vent regions, the distal flow margins southwest of the Devil’s Garden kipuka show evidence of lava-water interactions: steep flow margins with digitate planforms are consistent with water-enhanced cooling. Lava flow textures on a centimeter scale are neither smooth pahoehoe nor spikey a’a, also consistent with lava-water interactions. Lava flow surfaces within ~300 m of the distal flow margin are generally flat-lying with abundant lava-rise pits, indicating that the flow front was advancing more slowly than lava was being delivered to the flow front. These observations are consistent with the distal margin encountering ponded water or water-saturated ground. More exploration is needed to identify the limits of water-influenced lava emplacement.

Lava tubes, channels, and inflation features are observed throughout the flow field. We employed a range of field techniques to measure portions of the interior of Derrick Cave (a partially drained lava tube) and a lava channel adjacent to the northern flow margin (a.k.a. “the gutter”).  Derrick Cave is up to ~14m tall in cross-section, and smaller tubes (<4m across) are observed in the cave walls. Locally, layered pahoehoe lavas are revealed in the cave walls as well. Similarly, “the gutter” is a roughly trapezoidal-shaped channel in cross-section, and the channel walls (generally <5 m tall) reveal stacked pahoehoe lavas and lava tubes. The tube and channel properties suggest an eruption that lasted for months or years rather than hours or days. Future work will use detailed measurements collected in the field to model lava flow within the tubes and channels to constrain eruption rates and durations.

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