Читать книгу Geology For Dummies - Alecia M. Spooner - Страница 52

During World War I, a German scientist named Alfred Wegener suggested that the continents had once been connected and had drifted apart. His ideas about continental drift — the movement of the continents — were based on fossil, rock, and stratigraphic evidence (which I discuss in detail in Chapter 8). However, he hadn’t worked out all the details – such as what force, or mechanism, propelled the continents. At the time, scientific understanding of the earth’s crust as a continuous, solid, rigid layer did not allow for moving continents, and without a clear explanation for how they moved, Wegener’s hypothesis was strongly rejected by other geologists.

A dramatic breakthrough occurred in the decades after World War I when the use of submarines in warfare led to mapping of the seafloor with sonar. The 1960s in particular was a time of new discovery and understanding. Geologist Marie Tharp discovered a long, rocky ridge, a rift, in the middle of the Atlantic Ocean while drawing an ocean floor map from sonar data. (Her map, created with Bruce Heezen, is still the standard map of the ocean floor used by all scientists.)

The idea of seafloor spreading — the moving apart of oceanic crust along ridges on the ocean floor — was being explored by scientists, led by the ideas of Harry Hess. But there were still many who “knew” the earth’s crust and the mantle below were solid rock and could not be moving. One skeptic, Canadian geologist J. Tuzo Wilson, eventually published his ideas about plates moving across hotspots (see Chapter 10 for details) and his ideas provided a foundation on which the unifying theory of geology was built. The theory of plate tectonics combines ideas about plate movement with evidence for seafloor spreading, as well as incorporating explanations for volcanoes, earthquakes, and other geologic features and phenomena. Because this theory is so crucial, I devote Part 3 of this book to it.

Scientists never stop exploring, of course, so even with a well-accepted, well-tested explanation of how the surface of the earth constantly transforms, they don’t stop asking questions.