ABSTRACT
In the first decade of the twentieth-century there appeared a few scientists who can now be seen as the originators of modern 'earth science': men whose research covered geology, meteorology, and anything else there was to be studied about the physical workings of planet earth. Two of them stand out. Andrija Mohorovicic in Croatia for discovering the boundary between the earth's outer crust and its underlying mantle. Alfred Wegener in Germany propounded a hypothesis that earth's continents are not static, but are slowly on the move. Geophysicists, whose speciality is the structure and composition of our own planet, cannot visit its depths to see for themselves. Geologists invented instruments with which to record the vibrations produced by earthquakes, as they travelled across the earth's surface and through its interior. In the last three decades of the twentieth-century research on the ocean floors intensified, much of the earth's surface in order to test the plate tectonic theory of geology.
