Mapping Volcanic Ejecta Using Airborne Ice-Penetrating Radar in Marie Byrd Land, Antarctica

Marie Byrd Land (MBL) is a volcanically active region of West Antarctica covered by the West Antarctic Ice Sheet (WAIS). Several volcanoes outcrop throughout MBL and a number of subglacial ones have been identified using airborne geophysical data. Though the time of volcanic activity in MBL is broadly known (Late Cenozoic to present), the exact timing of individual eruptions and the eruption frequency of volcanoes is still largely constrained due to the inaccessibility of volcanic products.

Here we use airborne ice-penetrating radar data to map the distribution of volcanic ejecta within WAIS. We interpret significantly brighter portions of englacial radar reflectors as ash deposits and large hyperbolas as discrete volcanic bombs along ash layers. Since englacial radar reflectors are interpreted as isochrones (paleo-ice surfaces of constant age), ash and bombs along dated isochrones can be used to estimate periods of volcanic activity. By mapping the distribution of ash, we also investigate the location of source volcanoes and estimate their frequency of eruptions.

Isochrones containing ash were first traced and extended through MBL using the seismic interpretation software Landmark Decision Space, adapted to display and interpret radar returns. Then, the extent of ash deposits and bombs was mapped along continuous isochrones. The high density of ash deposits and bombs in WAIS' stratigraphy suggests frequent eruptions in the Executive Committee Range volcanic chain region of MBL since the Last Interglacial.