Global Decoupling of Crust and Mantle - Implications for Topography, Geoid and Mantle Viscosity on Venus

Publication Type  Journal Article
Year of Publication  1992
Authors  Buck, W. R.
Journal Title  Geophysical Research Letters
Volume  19
Issue  21
Pages  2111-2114
Journal Date  Nov 3
ISBN Number  0094-8276
Accession Number  ISI:A1992JY49600002
Key Words  tectonics; model; constraints; rheology; flow

The surface of Venus is so hot that the lower crust may be weak enough to allow decoupling of mantle and crust. An analytic model of such decoupling assumes that the shallow mantle forms the top boundary layers of large scale mantle convection cells. Crustal flow is driven by the motion of the mantle and by topographically induced pressure gradients. The model predicts that the lowest lowlands are sites of mantle upwelling and thinner than average crust. Highlands are places where mantle downwells and the crust is thick. Surface heat flow is inversely correlated with elevation, consistent with recent estimates of brittle layer thickness variations on Venus. If the average crustal thickness is about 20 km then the average lower crustal viscosity must be close to 10(18) Pa s to allow decoupling. The observed amplitude of geoid highs over highlands requires an Earth-like increase in mantle viscosity with depth.


Jy496Times Cited:10Cited References Count:22

URL  <Go to ISI>://A1992JY49600002