National Geographic : 1985 Aug
National Geographic's new ATLAS OF NORTH AMERICA Space Age Portrait ofa Continent the rest of the state docked. Doonerak is made of rocks like those I saw on Pagan. "We are in the heart of a continent," says Jones. "Yet Doonerak had to have been an island once. Some people believe it's always been an appendage of North America. I think it rafted in from somewhere near Kamchatka. If we really knew how complex this state is, we'd pack up and go home. "But we are convinced that when we see all these pieces that have been swept togeth er, shoved up, and thrust over one another, we are looking at the way all continents form. That's the beauty of Alaska." Indeed, geologists have found some 200 terranes in western North America alone. HOW LONG has plate tectonics been going on? We cannot trace plate movements back with any confi dence much further than about 570 million years, to the onset of the Cambrian period. The paleomagnetic signatures of older rocks cannot be interpreted reliably, and in Precambrian rocks the fossil record almost disappears. Not until the Cambrian period did creatures evolve hard body parts, whose forms could be preserved in rock. Un fortunately, the Precambrian covers 90 per cent of the planet's lifetime. The onset of the Cambrian was, until only 150 years ago, the dawn of time to students of the budding science of geology. In the 1830s Professor Adam Sedgwick, one of geology's gentlemen pioneers, discov ered marine fossils atop the wild mountains of Snowdonia in northern Wales. Sedgwick was not as much a fossil man as his rival, Sir Roderick Murchison. He was more interest ed in reporting back to the Geological Soci ety of London that he had located the oldest rocks yet known to man. Nevertheless, Sedgwick's discovery fortified his belief that the Cambrian rock sequence, which he had named for the Latin word for Wales, record ed the creation of life. Our Restless PlanetEarth Seen as never before, Mount McKinley and its colossal cohorts fill a 120-kilometer-wide panoramaof the Alaska Range in this view featured in the National Geographic'sforthcoming Atlas of North America. By computer blending of elevation data with the visual truth of a Landsat image, scientists at the U. S. Geological Survey produced a vivid oblique view far beyond the capability of an ordinary camera lens. Combining the most advanced mapping techniques with dozens of remote sensing satellite images, the new atlas paints a space-age picture of our continent. Remnants of ancient landforms, 50 terranes plasteredone upon another,form Alaska-which did not exist 150 million years ago. Each new collision left its mark in the buckled landscape,from the Brooks Range to the southern Panhandle. The most colorful space-age atlas ever published! Includes 100 remarkable satellite images of North America... plus superb cartography: political, relief, recreational, and metropolitan maps... presented together to give you an entirely new view of our continent! Reserve your copy today.. Please send me National Geographic's new ATLAS OF NORTH AMERICA. Bill me at the price checked below, plus postage and handling, when shipped in November. If not satisfied, I may return the book without payment. (Check one box.) Q Deluxe Edition $39.95 O Regular Edition $29.95 00607 U.S . funds* 00605 U.S . funds* (includes magnifier scale and slipcase) *Canadian funds: $54.70 for Deluxe, $41.00 for Regular. NAME (Please print: gummed labels do not adhere to this surface). ADDRESS CITY, STATE/PROVINCE, COUNTRY ZIP/POSTAL CODE This atlas is available only by direct order from National Geographic Society. 61 Calif, Md., and Mich. residents will be billed applicable sales or use tax.