Well, when rocks break, at the point of
rupture stress, different types of waves are
sent out. The two of concern here are the
P and the S waves. The P waves
travel through solids , liquids and gases. The S
waves travel only through solids. Because
liquids and gases offer no resistance to shear,
no S waves propagate through a liquid or gas.
Hence, because the earth has a shadow zone, a
region where no S waves appear, we can infer the
presence of a liquid outer core.
Click Here to return to the search form.