Thickness Of Continental Lithosphere Research Articles

Continental lithospheric thickness and deglaciation induced true polar wander

The secular drift of the earth’s rotation pole, which is evident in ILS data, is a memory of the planet of the last deglaciation event of the current ice age. In order to fit the observed rate and direction of drift with an earth model whose viscosity profile is capable of reconciling the free air gravity and relative sea level data of postglacial rebound, requires a lithospheric thickness which is substantially in excess of that which might be considered an appropriate average thickness for the entire planet. This required thickness, which is greater than 250 km, is nevertheless in accord with independent estimates of the thickness of the continental lithosphere.

Geoid anomalies and the thickness of the lithospere

Over broad regions of the earth, such as stable continental interiors and deep ocean basins, isostatic equilibrium is a good approximation. The isostatic requirement relates the density distributions in the continental and oceanic lithospheres. These density distributions are the result of differences in both composition and temperature. In regions of isostatic equilibrium the dipole moment of the near‐surface density distribution is proportional to the local geoid anomaly. By using accepted crustal density distributions and either error function or linear temperature distributions the difference in geoid height between stable continental areas and deep ocean basins has been determined as a function of the continental lithospheric thickness. If the continental lithosphere were greater than 200 km thick, the geoid anomaly over the continents would be systematically negative in relation to that over the ocean basins. By using the GEM 9 satellite geoid the mean geoid anomalies over ocean basins and stable continental areas have been obtained. No systematic difference between continental and oceanic geoids is observed. We conclude from our geoid studies that the thickness of the continental lithosphere is near 180 km. This is in good agreement with various interpretations of the surface heat flow observations.