Ocean floor spreading explains how and why the lithosphere moves, and how oceans are created and destroyed. It also confirms the permanence of continents and ties together and explains many of the features and processes that were originally thought to be isolated. But what about continental drift, the idea that started this revolution in thinking in the first place? With an active asthenosphere and lithosphere, there is no longer a need to search for a cause. Entrained in the plate system, continents move along the surface of the earth like ponderous rafts, impervious to sinking. They collide, expand, and refragment over the eons of geologic time. 

Since Wegener's time several additional lines of evidence have been added to his original ones, and even his ideas have been highly refined. Much of the more detailed evidence centers around discoveries in the southern continents because they were separated from each other later than the northern continents. 

Just as paleomagnetism was critical to an understanding of seafloor spreading, so it has helped our ability to track continents over time. Lavas cooling on continents also retain the magnetism prevalent at the time of their formation. If the continents have not moved over time, then we would expect that lavas of the same age in different continents would show the same magnetization and indicate the same magnetic poles. Such is not the case however. Each continent shows a different magnetic north pole. We are left with the conclusion that either there was more than one North Pole in the past or, more reasonably, that the continents have moved over time. Indeed, magnetic pole locations of individual continents plotted over time allow us to reconstruct the relative paths they followed over time. 

Detailed and refined bathymetric surveys have confirmed the amazing fit of the continents and the match in patterns of rock layers . Not only is there a match in the appearance of the layers, but also in their age and structure (folding and faulting). 

Over the years, additional information has been gathered on fossils, which had originally been one of the strongest line of evidence for continental drift. Today there is hardly any major group of animals or plants which does not show some evidence of having its patterns of evolution influenced by continental drift. The old explanation of land bridges connecting continents and providing a convenient route for migrations received its death blow when exploration of the ocean floor indicated that the foundered bridges which should have provided these avenues of access were nowhere to be found. (It is worth noting in this context that Atlantis and other mythical landmasses that supposedly sank into the ocean, also cannot be found despite detailed scrutiny of the ocean floor). 

The evidence which emerged from the study of ancient tillites, rocks formed during ancient glaciations in the southern continents, is equally striking. Their presently fragmented distribution shows little logical pattern. Even more curiously, when viewed from the standpoint of modern geography, the direction of motion of these past glaciers makes little sense. In India and South America it would appear from the direction of motion that can be inferred from the glacial striations, that the ice came crawling out of the ocean to erode the land. When the continents are returned to their pre drift positions, however, the ice center is clearly shown to lie in South Africa and to have spread outward from there