It has been said that science may be divided into two categories, astronomy which covers all things outside the Earth, and geophysics which deals with everything else. The geophysicist is dedicated to the study of the earth by physical means, and the Earth as a whole is his sphere. This is perhaps the biggest difference between the geophysicist and the geologist, for present geological techniques are based only on the study of the features of the Earth which are disclosed at the very surface of it. Although this sometimes gives a clue as to conditions at some depth below the surface, it is only by physical methods such as measurement of the Earth's gravity or magnetic fields, by the study of its thermal regime or of seismic waves that have traversed it that reliable information can be obtained about the interior of the Earth. It is at the surface that the geologists and geophysicists meet, and theories must be made to coincide. Nowhere is this common meeting ground more important than in Antarctica, for over most of the continent the ice sheet deprives the geologist of his access to the true surface of the solid earth.
