In the decade following W.W.II, spurred by all the technological advances made during the war, exploration of this planet made great strides. By the late 1950s, there had been a tremendous accumulation of facts and startling new discoveries had been made about the ocean floor. 

While direct exploration by drilling and by manned submersibles may be the best way of exploring the ocean floor, such explorations are slow, expensive and dangerous. Most of today's work uses remote sensing devices. They include sonar, especially the newer side-scan sonars, magnetometers, heat detectors, cameras taking still and movie pictures both underwater and from satellites in space, and such time honored techniques as dredging and seismic surveys. 

All these techniques provided new facts indicating that oceans and continents were clearly different. Among others we list: · 

• A distinct topography (see section on the earth's surface features). 
• Oceans are comparatively young. None is older than about 170 million years. In contrast, continents are hundreds of millions or billions of years old. 
• Oceans are youngest near ridges, and become progressively older outward Continents are oldest in their center and are younger at their margins. 
• Oceans are areas of relatively large heat loss, especially along the rift areas. Heat loss is lower in continental areas. 
• Oceans are basaltic, continents granitic. 
• Oceanic mountains, (the ridge), are usually located near the center of oceans. Continental mountains are commonly located near the margins of continents. 
• Oceanic ridges are basaltic and have rifts running along their axes. Continental mountains are deformed wedges of sediments, and have no rifts.

As lavas cool, the iron oxides they contain acquire the magnetization of the earth's magnetic field. This magnetic field constantly changes over time, and at times, the field's polarity has been reversed compared to the present polarity. During such times of reversal, a compass needle would point South instead of North. Any newly forming lava acquires the unique magnetic pattern prevalent at the time of its formation. 

Investigation of the magnetization of the ocean floor by Vine and Matthews showed that the ocean floor had a symmetrical pattern of magnetization on either side of the mid-ocean rift in site after site. Such a pattern can only be explained if we accept the idea that a commonly magnetized layer has been pulled apart. In turn, this could only be true if the ocean floor was rifting and spreading laterally as Hess suggested, and thus leads to these layers of similar magnetism hundreds and thousands of miles apart on either side of the rift. 

By the late sixties, there was little doubt in most investigators’ mind that the earth’s lithosphere was not a static rigid shell, but that it was made up of pieces of varying sizes called plates all moving on top of the asthenosphere, perhaps being driven by the convection currents Holmes has envisioned. Because it is difficult to conceive of moving ocean floors but static continents, it became clear that continents also were part of this moving system of plates. While many of the details were yet to be worked out, Wegener’s basic idea that continents had moved became the accepted view. Since that time, plate motion has been confirmed by geodetic satellites. More detailed views of the oceanic layers have also been received from an ambitious ocean-drilling program that has been going on for over two and a half decades (since 1968). This drilling has allowed us to determine the ages of the oceanic materials and confirmed spreading rates and magnetostratigraphy. 

Thus, a little over a century after organic evolution had been accepted by the biological community, the geological community in turn, came to envision an active and changing world, whose upper surface is composed of plates in continual motion. This modern unifying model that includes both ocean floor spreading and continental drift as its components is called the Plate tectonics theory or model.