Scientists at NASA's Jet Propulsion Laboaratory in Pasadena, CA have made the first extensive map of fluxuations in
Earth's gravity field, providing proof of "space warping", one of the keystones to Einstein's General Theory of Relativity.
Two earth-orbiting satellites, part of the Gravity Recovery And Climate Experiment (GRACE) Project have mapped the gravimetric fluxuations as part of a five year study to determine whether the Earth affects local space-time via an effect known as "frame dragging" (the article provides a good layman's explanation). One of the things noted in the article is that physical features (i.e. mountains, oceans, etc.) seem to have some bearing on the amount of localized drag, which makes sense, given that there is going to be significant differences in mass, which of course is a function of gravimetric strength.
Here's a map showing localized fluxuations (Warmer colors indicate above-normal gravity, cooler below-normal):
Now, what's interesting about this image is that it clearly shows above normal gravitation in very specific locations on the globe, including around the Pacific Rim, which upon closer inspection corresponds exactly to what geologists refer to as "The Ring Of Fire", a region of significant volcanic activity:
I'm no physicist nor geologist or vulcanologist, but even I can figure out that hat this seems to indicate is that there may be a connection between volcanic activity and gravimetric displacement; that is, gravity tends to be slightly higher where volcanic activity is present, and I guess the question this begs is, "why?" Magma isn't necessarily denser than solid matter, but it is generally under tremendous pressure; the grinding together of continental shelves for example, where one mantle is subsumed beneath another (as occurs just off our own coast), creates a tremendous amount of pressure, which in effect turns solid rock molten. So, would that possibly mean there may be some correlation between gravity fluxuations and an increase in dynamic pressure, all other things being more-or-less equal?
I really don't know, but it's an interesting speculation...
on 2:34 PM