%0 Journal Article
%A Romeo Briones, Ignacio
%A Turcotte, Donald L. (Donald Lawson)
%T The frequency-area distribution of volcanic units on Venus:Implications for planetary resurfacing
%D 2009
%@ 0019-1035
%U https://hdl.handle.net/20.500.14352/49725
%X The areas of volcanic units on Venus have been measured on the 1:5000000 geological maps published byNASA/USGS. These data were used to obtain a frequency-area distribution. The cumulative frequency-areadistribution of 1544 specific occurrence of units cover six orders of magnitude from the largest unit(30  106 km2) to the smallest (20 km2). The probability distribution function has been calculated. Themedium and large volcanic units correlate well with a power-law (fractal) relation for the dependence offrequency on area with a slope of 1.83. There are fewer small units than the expected values providedby the power-law relation. Our measurements cover 21.02% of the planetary surface, 3.59% of the study areawas found to be tessera terrain and is excluded from this study of volcanism. The measurements wererestricted to areas where geological maps have been published. The analysis was performed on two independentareas of the planet, with a complete coverage of published maps. In both areas the largest volcanicunit covers a significant portion of the surface (58.75% and 63.64%, respectively). For the total measured volcanicunits (excluding tessera), these two largest units (that could correspond to the same unit or not) coverthe 61.18% and they are stratigraphically superimposed on older volcanic units which cover 3.37% of thearea. The remaining area (35.45%) is occupied by younger volcanic units stratigraphically superimposedon the large volcanic unit(s). These results are based on the independent mapping of a large number of geologistswith different ideas about the geodynamical evolution of Venus and different criteria for geologicalmapping. Despite this fact, the presence of these very large units is incompatible with the equilibrium resurfacingmodels, because their generation at different ages would destroy the crater randomness. Our frequency-area distribution of the mapped volcanic units supports a catastrophic resurfacing due to theemplacement of the largest unit(s) followed by a decay of volcanism. Our data for the frequency-area distributionof volcanic units provide new support for catastrophic resurfacing models. It is difficult to makeour observations compatible with equilibrium, steady-state resurfacing models.
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