• Question: Are there rocks that can make gravity high?

    Asked by sciencekid to Paul on 23 Jun 2010 in Categories: .
    • Photo: Paul Roche

      Paul Roche answered on 23 Jun 2010:

      There are certainly rocks that are very dense, like basalt and granite, and if you have a very sensitive instrument to measure the local pull of gravity, it will feel a tiny bit stronger over areas made of these dense rocks.

      When I did geophysics at university, we did a lot of gravity surveys – it is a very good way to identify the location of dense rocks under the surface, but also for finding low density rocks that might contain oil or gas (as they have the opposite effect).

      So the rocks don’t “make gravity high”, but you can certainly measure a slightly stronger downward pull from gravity if you are over them.