Ambient effects on basalt and rhyolite lavas under Venusian, subaerial, and subaqueous conditions

Bridges, N. T.

doi:10.1029/97je00390

Cited by 39 publications

(43 citation statements)

References 73 publications

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“…They found that a range of physical properties (i.e., initial viscosity and crystal content) corresponding to compositions from basaltic to rhyolitic could explain steep-sided dome morphology and favored basaltic compositions for the domes [Sakimoto and Zuber, 1995]. Analyses by Bridges [1997Bridges [ , 1997 noted similarities in dimensions and appearance between Venusian steep-sided domes and basaltic seamounts.…”

Section: Introductionmentioning

confidence: 99%

“…They showed more than 500 ø of cooling for basaltic lava flows surfaces on both Earth and Venus in this time period, though <100 ø of this occurs after the first 100 s, during which the upper surface is quenched. As described above, Bridges [1997] Table 1 for model parameters. This approach also assumes that the surface temperature remains at a constant value.…”

Section: Model Of Crustal Formationmentioning

confidence: 99%

“…Bridges [1997] and Manley, 1987;Manley and Fink, 1987;Anderson and Fink, 1990]. In addition, the types, orientations, and distributions of surface features, such as ridges, fractures, creases, inflation structures, and blocks, provide constraints regarding the stress/strain histories of flow surfaces during emplacement [Nichols, 1939;Fink and Fletcher, 1978;Fink, 1980aFink, , 1980bFink, , 1983Fink, , 1985 .…”

Section: Introductionmentioning

confidence: 99%

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Emplacement and composition of steep‐sided domes on Venus

Stofan¹,

Anderson²,

Crown³

et al. 2000

J. Geophys. Res.

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Abstract. Steep-sided domes on Venus have surface characteristics that can provide information on their emplacement, including relatively smooth upper surfaces, radial and polygonal fracture patterns, and pits. These characteristics indicate that domes have surface crusts which are relatively unbroken, have mobile interiors after emplacement, and preserve fractures from only late in their history in response to endogenous growth or sagging of the dome surface. We have calculated the time necessary to form a 12-cm-thick crust for basalt and rhyolite under current terrestrial and Venusian ambient conditions. A 12-cm-thick crust will form in all cases in < 10 hours. Although Venusian lava flows should develop a brittle carapace during emplacement, only late-stage brittle fractures are preserved at steep-sided domes. We favor an emplacement model where early-formed surface crusts are entrained or continually annealed as they deform to accommodate dome growth. Entrainment and annealing of fractures are not mutually exclusive processes and thus may both be at work during steep-sided dome emplacement. Our results are most consistent with basaltic compositions, as rhyolitic lavas would quickly form thick crusts which would break into large blocks that would be difficult to entrain or anneal. However, if Venus has undergone large temperature excursions in the past (producing ambient conditions of 800-1000 K [e.g., Bullock and Grinspoon, 1996, 1998]), rhyolitic lavas would be unable to form crusts at high surface temperatures and could produce domes with surface characteristics consistent with those of Venusian steep-sided domes.

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Section: Introductionmentioning

confidence: 99%

Section: Model Of Crustal Formationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Emplacement and composition of steep‐sided domes on Venus

Stofan¹,

Anderson²,

Crown³

et al. 2000

J. Geophys. Res.

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“…The Magellan radar mapping mission to Venus revealed a variety of volcanic features, and the interpretation of the radar images inspired a number of studies utilizing radar remote sensing of terrestrial volcanoes and lava flows [e.g., Greeley and Martel, 1988;Ford et al, 1989;Gaddis et al, 1989Gaddis et al, , 1990Campbell and Campbell, 1992;Arvidson et al, 1993;Mouginis-Mark, 1995;Campbell and Shepard, 1996]. A remarkable finding from Magellan was a class of apparently volcanic landforms referred to as ''steep-sided'' or ''pancake'' domes Pavri et al, 1992;McKenzie et al, 1992;Fink et al, 1993;Bridges, 1997;Stofan et al, 2000]. The gross morphology of these features was reminiscent of silicic lava domes on Earth, and early workers suggested that they represented viscous lava flows, silicic in composition [McKenzie et al, 1992] or alternatively, less silicic lavas with enhanced gas bubble content [Pavri et al, 1992].…”

Section: Introductionmentioning

confidence: 99%

The unique radar properties of silicic lava domes

et al. 2004

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[1] Silicic lava domes exhibit distinct morphologic characteristics at scales of centimeters to kilometers. Multiparameter radar observations capture the unique geometric signatures of silicic domes in a set of radar scattering properties that are unlike any other natural geologic surfaces. Backscatter cross-section values are among the highest observed on terrestrial lava flows and show only a weak decrease with incidence angle. Crosspolarization backscatter (HV) shows a unique behavior, increasing with increasing wavelength. Circular polarization ratios are relatively high, in the 0.3-0.95 range, and increase with increasing wavelength. Field measurements of boulder size frequency distributions and microtopography indicate that silicic dome surfaces are among the roughest ever measured. Rms heights at a 1 m lateral scale range from 13 cm to 50 cm. Rms slopes at 1 m spacing range from 12 to 43 degrees. Modeling of the scattering behavior suggests it results from a combination of rough surface (facet) scattering and scattering from block edges that act as a random collection of dipoles. The unusual wavelength dependence of the radar parameters appears to result from a higher component of edge scattering at large wavelengths, producing, for example, higher cross-polarized backscatter at P band (68 cm). Steep-sided volcanic domes on Venus superficially resemble terrestrial silicic domes in plan view gross morphology, but few similarities remain when the radar scattering and three-dimensional shapes of the features are compared. The unique radar scattering properties suggest that such volcanic surfaces can be identified with multiparameter radar observations in future planetary radar missions and in active terrestrial volcanoes, where dome development can represent serious hazards.

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“…The major volatile 30 component is usually water, which may be sourced directly from fertile mantle in basalts 31 (Green, 1973) or enriched in evolved magmas through dehydration of subducted crust at 32 convergent plate margins. Magellan imagery and Venera lander data (Surkov and Barsukov,33 1985) imply that the majority of Venus' volcanics are basaltic in composition, although there 34 is some evidence for compositions richer in silica (Fink et al, 1993, Bridges, 1997 2013), sulphate (Kargel et al, 1994) or carbonate (Williams-Jones et al, 1998, Komatsu et 36 al., 2001), the latter of which implies silica-poor evolved magmas (Hess and Head, 1990) that 37 erupt effusive low viscosity flows. The interior is extremely dry with respect to water, with 38 perhaps only 50 ppm water in basaltic magmas (Grinspoon, 1993).…”

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confidence: 99%

A pyroclastic flow deposit on Venus

Ghail

Wilson

2013

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8 Explosive volcanism on Venus is severely inhibited by its high atmospheric pressure and lack of 9 water. This paper shows that a deposit located near 16°S, 144°E, here referred to as Scathach Fluctus, 10 displays a number of morphological characteristics consistent with a pyroclastic flow deposit. These 11 characteristics, particularly its lack of channelisation and evidence for momentum rather than cooling 12 limited flow length, contrast with fissure-fed lava flow deposits.

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Ambient effects on basalt and rhyolite lavas under Venusian, subaerial, and subaqueous conditions

Cited by 39 publications

References 73 publications

Emplacement and composition of steep‐sided domes on Venus

Emplacement and composition of steep‐sided domes on Venus

The unique radar properties of silicic lava domes

A pyroclastic flow deposit on Venus

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