Pyroclastic flow deposits on Venus as indicators of renewed magmatic activity. Issue 7 (26th July 2017)

• Record Type: Journal Article
• Authors: Campbell, Bruce A.; Morgan, Gareth A.; Whitten, Jennifer L.; Carter, Lynn M.; Glaze, Lori S.; Campbell, Donald B.
• Is Part Of: Journal of geophysical research. Volume 122:Issue 7(2017)
• Page Start: 1580
• Page End: 1596
• Publication Date: 2017-07-26
• Subjects: Venus -- volcanism -- radar; Planets -- Periodicals; Geophysics -- Periodicals; 559.9
• DOI: 10.1002/2017JE005299
• Languages: English
• ISSNs: 2169-9097

Abstract

Abstract: Radar bright deposits on Venus that have diffuse margins suggest eruptions that distribute debris over large areas due to ground‐hugging flows from plume collapse. We examine deposits in eastern Eistla, western Eistla, Phoebe, and Dione Regiones using Magellan data and Earth‐based radar maps. The radar bright units have no marginal lobes or other features consistent with viscous flow. Their morphology, radar echo strength, polarization properties, and microwave emissivity are consistent with mantling deposits composed of few centimeters or larger clasts. This debris traveled downhill up to ~100 km on modest slopes and blanketed lava flows and tectonic features to depths of tens of centimeters to a few meters over areas up to 40 × 10 3 km 2 . There is evidence for ongoing removal and exhumation of previously buried terrain. A newly identified occurrence is associated with a ridge belt south of Ushas Mons. We also note radar bright streaks of coarse material west of Rona Chasma that reflect the last traces of a deposit mobilized by winds from the formation of Mirabeau crater. If the radar bright units originate by the collapse of eruption columns, with coarse fragmental material entrained and fluidized by hot gases, then their extent suggests large erupted volatile (CO2 or H2 O) amounts. We propose that these deposits reflect the early stage of renewed magmatic activity, with volatile‐rich, disrupted magma escaping through vents in fractured regions of the upper crust. Rapidly eroding under Venus surface conditions or buried by subsequent eruptions, these markers of recently renewed activity have disappeared from older regions. Plain Language Summary: We map deposits on Venus formed by the collapse of volcanic eruption plumes or fire fountains. These deposits are made up of small rocks fragmented during the eruption, extend up to 100 km from their sources, and cover areas of up to 40, 000 km 2 . The rough material covers older lava flows and is being eroded relatively quickly in the harsh environment. We propose that these deposits are evidence for the first stage of eruptions from new batches of magma and that their locations represent some of the youngest volcanically active places on Venus. Key Points: We map deposits on Venus formed by collapse of volcanic eruption columns Radar properties suggest that the deposits are made up of coarse clastic debris We propose that these deposits mark sites of renewed magmatic activity