Introduction

The Earth is a water planet with about 71 percent of the surface covered with water. This water cover prevented study of the deep submerged ocean floors until technological developments allowed improved surveys of ocean areas. Part of the reason that a revolution in geological thinking about tectonics came late is that collection of data from oceanic areas is a capability resulting from research techniques developed after 1950. In this chapter, we will examine the origin of the earth, the tools used for investigation, the nature of the interior, prior tectonic theories and the modern theory of plate tectonics.