Seismic evidence for an equilibration mechanism between asthenosphere and surface temperature

Includes bibliographical references.Composite profiles of qlobal earthquake occurrences and of earthquake energy release versus latitude display a northerly skewed bimodal distribution that is highly correlated with surface temperature. Regressions of the earthquake data with the isostatic gravity anomaly, with heat flow, and with continental distribution yield correlations that are less significant. Since global seismicity is dependent on mantle viscosity, and hence, mantle temperature, the high correlation between surface temperature and seismicity suggests a direct relationship between surface temperature and mantle temperature as proposed by McGinnis (1979) and expressed in an equation from Verhoogen and others (1970): T[sub L] = T₀ + L(Q-0.5εL )k⁻¹, where T[sub L] is the temperature at the base of the lithosphere, T₀ is the surface temperature, and the term L(Q-0.5εL )k⁻¹ is assumed to be constant (McGinnis, 1 979). Since plate motion is thought to be due to a convecting mantle, a rise in mantle temperature should be accompanied by increased convection and lead to greater plate motion, with a resulting rise in seismic and rifting activity. Assuming that the mantle beneath Pangaea was initially cooled by peripheral subduction, it follows that Pangaea should have been sundered by a sequence of rifting events originating near the warmer equator and eventually extending in to colder, higher latitudes. A review of the rifting history and the latitude of continents at the time of rifting corroborates this idea.M.S. (Master of Science