# Sea Floor Spreading Theory

# Back Ground and Theory for Sea Floor Spreading

**Cooling of the Oceanic Lithosphere and Ocean Floor Topography**

full on-line paper by David Sandwell (more info)

**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=-d_{o}-.11*sqrt(10 x/u)

where K = 1x10^{-6}m^{2}/s = 31.5 km^{2}/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, **d _{o}**, 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.