Sentences with phrase «sampling igneous rocks»

Not exact matches

Because we can not sample the deep Earth, we must deduce its composition either by looking at the clues hidden in igneous and metamorphic rocks, or by examining proxies for composition and structure such as the three - dimensional variation of the velocity of seismic waves produced by earthquakes and sampled by networks of seismometers on the surface.

Given that the seismic signature of this material is essentially the same as crustal igneous rocks, there is no way of telling - other than to drill and sample everything between the seabed and the top few hundred metres of unadulterated mantle.