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# Back Ground and Theory for Sea Floor Spreading

Cooling of the Oceanic Lithosphere and Ocean Floor Topography

This lecture is the development of the lithospheric cooling problem......

Sandwell outlines the derivation of calculating the ocean floor depth below the ridge using thermodynamics and structural arguments. We provide a very brief outline here and present the relevant equations in the form used by us for our Excel Sea Floor Spreading Activities (Activity I & Activity II).

Equation 37. from Sandwell except that we use distance over speed (x/u) in place of t.

Sketch of Model.

Model parameters

Using these constants we express the depth of the ocean floor below the oceans surface as

# d=-do-.11*sqrt(10 x/u)

where K = 1x10-6m2/s = 31.5 km2/Myr , p = 3.14, X is the horizontal distance from the ridge measured in km and u is the sea floor spreading rate in km/Myr. Where we have assumed that the ridge is a depth, do, below the oceans surface. This gives use three adjustable parameters to use for our Excel assignments in Activity I & Activity II.

## Reference

A complete derivation of equation 37 is also contained in:

Geodynamics Second Eddition by Donald Turcotte and Gerlad Schubert, Cambridge University Press, 2002.