I read a recent article in <i>Science</i>, summarized here (<a href="http:&#x2F;&#x2F;science.sciencemag.org&#x2F;content&#x2F;349&#x2F;6252&#x2F;1032.short" rel="nofollow">http:&#x2F;&#x2F;science.sciencemag.org&#x2F;content&#x2F;349&#x2F;6252&#x2F;1032.short</a>), on tomographic analysis of Earth&#x27;s mantle using data recovered during large earthquakes.  The large plumes that, for example, create volcanic islands like Hawaii turn out to be ~600km wide, and extend to ~3000 km below the surface.<p>It was not known previously how deep these plumes go.  Many thought they were much smaller and shallower.<p>It&#x27;s in some sense surprising that even basic facts like this are the current frontier.