Modeling the Dynamics of Dense Pyroclastic Flows on Venus: Insights Into Pyroclastic Eruptions

Ganesh, I.; McGuire, Luke A.; Carter, Lynn M.

doi:10.1029/2021je006943

Cited by 9 publications

(8 citation statements)

References 102 publications

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“…Taken together, these observations suggest that these bright regions are rough mantling pyroclastic flow deposits that are at the top of the stratigraphic column (Campbell et al 2017). Modeling suggests that the deposits could have been formed through column collapse or perhaps long duration fire-fountaining, with thicknesses ranging from meters to tens-of-meters (Ganesh et al 2021). Their presence indicates that significant volatiles (CO 2 , H 2 O) must have been present (Airey et al 2015), and such volatile-rich eruptions are more typical in the early stages of volcanic eruptions (Campbell et al 2017).…”

Section: Radar Properties Of Potential Young Pyroclasticsmentioning

confidence: 80%

Resurfacing History and Volcanic Activity of Venus

et al. 2023

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Photogeologic principles can be used to suggest possible sequences of events that result in the present planetary surface. The most common method of evaluating the absolute age of a planetary surface remotely is to count the number of impact craters that have occurred after the surface formed, with the assumption that the craters occur in a spatially random fashion over time. Using additional assumptions, craters that have been partially modified by later geologic activity can be used to assess the time frames for an interpreted sequence of events. The total number of craters on Venus is low and the spatial distribution taken by itself is nearly indistinguishable from random. The overall implication is that the Venusian surface is much closer to Earth in its youthfulness than the other, smaller inner solar system bodies. There are differing interpretations of the extent to which volcanism and tectonics have modified the craters and of the regional and global sequences of geologic events. Consequently, a spectrum of global resurfacing views has emerged. These range from a planet that has evolved to have limited current volcanism and tectonics concentrated in a few zones to a planet with Earth-like levels of activity occurring everywhere at similar rates but in different ways. Analyses of the geologic record have provided observations that are challenging to reconcile with either of the endmember views. The interpretation of a global evolution with time in the nature of geologic activity relies on assumptions that have been challenged, but there are other observations of areally extensive short-lived features such as canali that are challenging to reconcile with a view of different regions evolving independently. Future data, especially high-resolution imaging and topography, can provide the details to resolve some of the issues. These different global-evolution viewpoints must tie to assessments of present-day volcanic and tectonic activity levels that can be made with the data from upcoming missions.

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Section: Radar Properties Of Potential Young Pyroclasticsmentioning

confidence: 80%

Resurfacing History and Volcanic Activity of Venus

et al. 2023

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“…A handful of radar-bright deposits on the surface of Venus have been tentatively identified as pyroclastic materials (Campbell et al 2017). Radar brightness suggests that clasts with diameters of at least a centimeter are present throughout the deposits and were deposited there after traveling tens of kilometers in a pyroclastic density current (Ganesh et al 2021). Erosion of these pyroclastic materials should produce transportable sand-sized particles (Kreslavsky & Bondarenko 2017).…”

Section: Pyroclastic Materialsmentioning

confidence: 99%

“…Pyroclastic flow volumes are small (e.g., ∼21 km 3 for a pyroclastic field at Ushas Mons; Campbell et al 2017), but an abundance of such deposits could potentially produce a large volume of additional sand. Ganesh et al (2021) estimated the bulk volumes for extensive pyroclastic deposits located in Eistla Regio: 310-780 km 3 for the large deposits at Irnini Mons and 140-280 km 3 for the smaller deposits at Anala Mons, Pavlova, and Didilia coronae. Between ∼5 and 75 pyroclastic flow events of these sizes would yield enough sediment to account for the missing volume in both fields.…”

Section: Pyroclastic Materialsmentioning

confidence: 99%

Reassessment of the Volumes of Sediment Sources and Sinks on Venus

Ganey¹,

Gilmore²,

Brossier³

2023

Planet. Sci. J.

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The dominant source of sediment on Venus is thought to be impact cratering, wherein crater ejecta is redistributed across the planet by winds. Here we provide a refined global sediment budget for Venus by mapping and quantifying the volume of sediment from impact craters observable in Magellan data using updated methodology. We improve on previous estimates of the volume of impact-generated sediment by mapping the impact deposits for all craters ≥11 km on Venus. We estimate the planet’s total budget of impact sediment to be a minimum of 290,000 km3, which corresponds to a global layer of sediment 63 cm thick. If erosional processes have been active over the average surface age (500 Ma–1 Ga), the transportable fraction of this volume implies a sediment mobilization rate between 0.18 and 0.36 nm yr−1, comparable to the late Hesperian–Amazonian era of Mars. We requantify the volume of sediment held in recognized eolian features by (1) applying morphometric studies of planetary analogs to assess the volumes of observed Venusian dune and yardang fields and (2) estimating the volume of proposed microdune fields. We also identify a new yardang field near Mead crater. Globally, we find that >100,000 km3 of available sediment is not accounted for by eolian deposits, concurring that lithification, resurfacing, and fields of as yet unidentified eolian features are other potential sinks for sediment. However, locally, individual eolian fields contain more sediment than can be derived from nearby craters, indicating that these fields contain additional sediment from other sources.

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“…The PDC deposit stratigraphy proposed by Campbell et al (2017), of a few tens of centimeters to a meter thick mantling layer on top of older substrate, could lead to radar wave penetration and scattering from buried features. Volume scattering from buried clasts or void spaces would be an important contribution if the PDC deposits are even thicker, on the scale of tens of meters as suggested by Ganesh et al (2021).…”

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confidence: 94%

Radar Backscatter and Emissivity Models of Proposed Pyroclastic Density Current Deposits on Venus

2022

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Magellan synthetic aperture radar observations of Venus revealed a small number of deposits in the highland regions that were suggested to have formed from pyroclastic density currents. Studying these deposits is useful for understanding the nature of pyroclastic activity and eruptive history on Venus. The proposed pyroclastic deposits occupy the uppermost unit in local stratigraphy and are found near exceptionally high reflectivity (R $R$∼0.6) units in the highlands. Their radar properties include high copolarized backscatter (∼−8 to −15 dB) and moderate emissivity values (∼0.70–0.88) in the 12.6 cm wavelength Magellan data acquired at incidence angles between ∼15° and 45°. We aim to characterize the structure of these deposits by modeling the observed backscatter and emissivity as a function of different physical and dielectric properties and shallow subsurface stratigraphy. Three different physical scenarios focusing on three different scattering mechanisms—surface scattering, subsurface scattering from buried dielectric horizons, and volume scattering from buried, distributed scatterers—are considered. By comparing the model results to Magellan observations, we narrow down likely pyroclastic deposit structures. We show that the deposits are likely analogous to dense, welded ignimbrites with high surface roughness. We also investigate other possible but less likely scenarios of a thin, low‐density, low‐loss mantling pyroclastic deposit on top of high reflectivity units and a thick, low‐density, low‐loss deposit with ∼5–10 volume % of scatterers of sub‐wavelength size. Future multiwavelength, multipolarization radar observations from VERITAS and EnVision may enable unambiguous characterization of these deposits.

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Modeling the Dynamics of Dense Pyroclastic Flows on Venus: Insights Into Pyroclastic Eruptions

Cited by 9 publications

References 102 publications

Resurfacing History and Volcanic Activity of Venus

Resurfacing History and Volcanic Activity of Venus

Reassessment of the Volumes of Sediment Sources and Sinks on Venus

Radar Backscatter and Emissivity Models of Proposed Pyroclastic Density Current Deposits on Venus

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