Isostatic Balancing of Lithospheric Columns

A Special Case of Local Isostasy

Based on the Mantle Geoid Concept (Turcotte and others, 1977)

Use this page to find the thickness of the mantle lid (subcrustal lithosphere) of a transect of lithospheric columns. This is a local-isostatic approach, meaning each lithospheric column floats independently on the asthenosphere (no flexure). This assumption is most reasonable when flexural rigidity of the lithosphere is low. The approach used is based on the "mantle geoid" concept of Turcotte and others (1977). The underlying idea is that we can use mid-ocean ridges as reference columns, since the asthenosphere is loaded only by water and a thin basaltic crust. This gives us an indication of the elevation to which the asthenosphere would rise if there were no lithosphere (the so-called mantle geoid). If we assume local isostasy and known densities for various layers of the lithosphere, we can solve for the thickness of the mantle lid, given water depth, sediment thickness and the thickness and type of crust. This can be useful for predicting heat flow and thermal gradient in sedimentary basins, and for studying the interplay of variables such as thickness and density.

Start Over     Select any column then choose an action: Column 1 Column 2 Column 3 Column 4 Column 5 Column 6 Column 7 Column 8 Column 9 Column 10 Edit Remove Insert Before   Constants

    Water Depth (negative for elevations above SL, meters)           Sediment Thickness (m)
    Crustal Thickness (m)       Crustal Type Continental Transitional Oceanic        
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Geoid (mbsl)	Densities (kg/m3)
	Seawater:		Sediment:		Mantle Lid:		Asthenosphere:
Crust	Continental:		Transitional:		Oceanic:		OK	Cancel