Gravity of the Earth. Gravitational acceleration a distance r from a sphere of density ρ is This result is independent of radial density variations. Gravity of the Earth. The earth is not a perfect sphere but is approximately an oblate spheroid – an ellipse rotated about the short axis
Gravity anomaly (http://www.ncgia.ucsb.edu/education/curricula/giscc/units/u015/figures/figure04.gifmgal)
UK continental margin
All four density models (c, e, f, g) describe the observed gravity anomaly. There are actually an infinity number of density models that will produce the same gravity anomaly. This in another example of non-uniqueness.
What are the differences between each of the density models?
Model c is most consistent with what is understood about spreading centers.