Charles Darwin

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Cape Verde was where Charles Darwin first got off the Beagle with Charles Lyell’ s Principles of Geology in his hand, and quickly developed such admiration for Lyell’s presentation of the science. Had Lyell told him that the Cape Verde Islands had also been on a voyage-that in a deep geophysical sense they had come from New England-Darwin might have thrown the book overboard. Even on the best-defined tracks, not everything falls patly into place. There is zakelijke energie some granite in New Hampshire that is two hundred million years old-still too young to be part of the Appalachian orogenic story but too old to be explained in terms of the two passing hot spots that left other granites. Possibly the two-hundred-millionyear-old rock has something to do with magmas that came up at that time as the crust tore apart to admit the Atlantic. When Great Meteor arrived at the edge of the Canadian Shield, under the present site of Montreal, it presumably made the Monteregian hills, for one of which the city is named. The Monteregian hills are volcanic, but their potassium-argon age disagrees by twenty million years with the date when, by all other calculations, Montreal was over the hot spot-an exception that probes the tl1eory. Morgan attributes the inconsistency to “random things you can’t explain” and mentions the possibility of faulty dating. He also says, quite equably, “If the Monteregian hills really don’t Rt the model, you have to come up with another model.” The hot-spot hypothesis was put forward in the early nineteensixties by J. Tuzo Wilson, of the University of Toronto, as a consequence of a stopover in Hawaii and one look at the islands. The situation seemed obvious. James Hutton, on whose eighteenthcentury Theory of the Earth the science of geology has been built, understood in a general way that great heat from deep sources stirs the actions of the earth (”There has been exerted an extreme degree of heat below the strata formed at the bottom of the sea”), but no one to this day knows exactly how it works. Heat rising from hot spots zakelijke energie vergelijken apparently lubricates the asthenosphere-the layer on which the plates slide. According to theory, the plates would stop moving if the hot spots were not there. Why the hot spots are there in the first place is a question that seeks its own Hutton. For the moment, all Jason Morgan can offer is another shrug and smile. “I don’t know,” he says. “It must have something to do with the way heat gets out of the lower mantle.”

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