These eventually came to be regarded as rift valleys, for they proved to be the boundaries between separating plates. As early as i956, oceanographers at Columbia had assembled seismological data suggesting that a remarkable percentage of all earthquakes were occurring in the mid-ocean rifts-a finding that was supported, and then some, after a worldwide system of more than a hundred seismological monitoring stations was established in anticipation of the flexplek huren amersfoort nuclear-test-ban treaty of i963. If there was to be underground testing, one had to be able to detect someone else’s tests, so a by-product of the Cold War was seismological data on a scale unapproached before. The whole of plate tectonics, a story of steady-state violence along boundaries, was being brought to light largely as a result of the development of instruments of war. Earthquakes “focus” where earth begins to move, and along transform faults like the San Andreas the focusses were shallow. At the ocean trenches they could be very deep. The facts accrued. Global maps of the new seismological data showed earthquakes not only clustered all along the ridges of the seafloor mountains but also in the trenches and transform faults, with the result that the seismology was flexplek huren enschede sketching the earth’s crustal plates. To Rear Admiral Hess, as he had become in the U.S. Naval Reserve, it now seemed apparent that seafloors were spreading away from mid-ocean ridges, where new seafloor was continuously being created in deep cracks, and, thinking through as many related phenomena as he was able to discern at the time, he marshalled his own research and the published work of others up to ig6o and wrote in that year his “History of Ocean Basins.” In the nineteen-forties, a professor at Delft had written a book called The Pulse of the Earth, in which he asserted with mild cynicism that where gaps exist among the facts of geology the space between is often filled with things “geopoetical,” and now Hess, with good-humored candor, adopted the term and announced in his first paragraph that while he meant “not to travel any further into the realm of fantasy than is absolutely necessary,” he nonetheless looked upon what he was about to present as “an essay in geopoetry.” He could not be sure which of his suppositions might be empty conjecture and which might in retrospect be regarded as precocious insights.