ROCK CORRAL BUTTE, IDAHO: AN EXAMPLE OF SHIELD EMPLACEMENT BY PRIMARILY CONFINED FLOW WITH IMPLICATIONS FOR PLAINS-STYLE VOLCANISM

Interpreting and quantifying the range of volcanic morphologies observed on small (basal diameter <25 km) shield volcanoes on Earth can lead to a better understanding of analogous eruption and emplacement styles and durations on other rocky planets. Previous investigations of small shield volcanoes in the Eastern Snake River Plain (ESRP), Idaho, for example, reveal a range of eruption and emplacement styles (e.g., confined and unconfined flow). Rock Corral Butte (RCB) is a 50,000-year-old basaltic shield volcano located at 43° 22.25'N, 113° 1.20'W in the ESRP whose flow field extent is 15 km (north-south) by 7 km (east-west). This lava flow field displays morphologies that we interpret to have been generated almost entirely by confined lava flow processes. These morphologies include: tumuli, pressure ridges, lava-tube ridges, boccas, and more. For example, tumuli on this flow field range from football-shaped mounds that may be up to 10s of meters long with a well defined axial crack, to more circular basaltic mounds (10s of meters in diameter) that had their roof collapse after they were drained of their molten interior. Also, the RCB flow field displays a series of topographic steps composed of inflation features that decrease in elevation with distance from the vent. Typically, the steps are source regions for multiple subsequent lava-tube ridges and small (generally <1 m across and up to 10s of m long) elongate lobes.

To better understand these features we conducted a field campaign in July 2022 to RCB. We will present our preliminary results and describe how relevant they are to interpreting RCB’s eruptive processes as well as to small shield morphologies on the terrestrial planets.