New Hampshire

Gerelateerde afbeelding

Why were the granites of New Hampshire relatively young, and therefore anachronistic in the Appalachian story? What explained great crustal swells, like random blisters on the ocean floor, rising high above the abyssal plains? What could explain Bermuda-a mountain summit seventeen thousand six hundred and fifty-nine feet above the Hatteras Abyssal Plain? What created the Marshall Islands, the Gilbert Islands, the Line Islands, the Tuamotu Archipelago-where corals veneer the peaks of twentythousand-foot mountains that tend to run in chains? Like Yellowstone, like Bermuda, like Hawaii, like Mt. Cameroon, they lie great distances from the nearest intersections of plates. Yellowstone draws its name from rich golden splashes of chemically altered volcanic rock. The place smokes and spits-the effects of proximate magma. On a geologic map of North America, Yellowstone appears at the eastern end of a bright streak of volcanic debris, coming off it like a contrail, extending across Idaho. With distance from Yellowstone, rock on that track is progressively older, descending age by age to the Columbia River flood basalts, which emerged from the ground like melted iron in early Miocene time, spread out across three hundred thousand square kilometres (in some places two and three miles deep), filled the Columbia Valley, and pooled against the North Cascades. By comparing the dates of the rock, one could be led to conclude that the geologic phenomenon now called Yellowstone has somehow been moving east at a rate of two and a half zakelijke energie vergelijken centimetres a year. As it happens, that is the rate at which, according to plate-tectonic theorists, North America is moving in exactly the opposite direction. In increasing numbers, geologists have come to believe that in a deep geophysical sense Yellowstone is not what is moving. They believe that the great heat that has expressed itself in so many ways on the topographic surface of the modern park derives from a source in the mantle far below the hull of North America. They believe that as North America slides over this fixed locus of thermal energy the rising heat is so intense that it penetrates the plate. The geologic term for such a place is “hot spot.” The earth seems to have about sixty of them-most older, and many less productive, than Yellowstone. Despite its position under thick continental crust, the Yellowstone hot spot has zakelijke energie driven to the surface an amount of magma that is about equal to the over-all production of Hawaii, which has written a clear signature on the Pacific floor. Hawaii is the world’s most preserved and trackable hot spot.

Geef een reactie

Het e-mailadres wordt niet gepubliceerd. Vereiste velden zijn gemarkeerd met *