Alle berichten van admin

Historical geologists

Gerelateerde afbeelding

Historical geologists, in the olden days, pieced together that narrative. Economic geologists, in their pragmatic way, cared less. In describing the minable Martinsburg-the blue-gray true unfading slate-C. H. Behre, Jr., wrote in i933, “Sedimentary rocks are often compressed from the sides through what may be loosely described as shrinking of the crust of the earth; how this shrinking is brought about is, for the present purpose, beside the point. It has the wellrecognized effect, however, that layers or bedding planes are wrinkled or thrown into ‘folds.’ ” By the nineteen-seventies, what Behre had loosely described was widely believed to be the impact of one continent colliding with another, as Iapetus, tl1e proto-Atlantic ocean, was closed and the suture of the two continents became the spine of the Appalachians. The conference room amsterdam successive pulses of orogeny-Taconic, Acadian, Alleghenianwere attributed to the irregular shapes of shelves and coastlines of the continents. Where they bulged, the action would have an early date, and especially where some cape, point, or peninsula had a similar feature coming from the opposite side. Such headlands, in advance contact, were said to have produced the Taconic Orogeny. Great bays, eventually coming against one another, set off the Acadian Orogeny. The Alleghenian Orogeny was the final crunching scrum, completing the collision. The apparent suture was a line running through Brevard, North Carolina, more or less connecting Atlanta, Asheville, and Roanoke, not to mention Africa and America. The Martinsburg seafloor and the underlying carbonate rocks had unquestionably been broken into thrust sheets and shuffled like conference room eindhoven cards. Uplifted with their Precambrian basement, they had, in perfect harmony with the Old Geology, become mountains that shed their sediments-shed their elastic wedges-and buried the Martinsburg deep enough to turn it into slate, buried the carbonates deep enough to turn them into marble. Thus, plate tectonics fit. Plate tectonics may have restyled the orogeny and dilapidated the geosyncline, but it fit the classical evidence.

Illogically

Afbeeldingsresultaat voor site:ilocate.nl

Illogically, the one they drew did not run east to a point on the river close to the Water Gap but northeast on a vector that encompassed and annexed the Minisink. Massacres ensued. Buildings were burned. Up and down the river, white scalps were cut. The Lenape reached for “the French hatchet.” Peaceful, accommodating they once had been, but now they were participants in the French and Indian Wars. Where they had tolerated whites in the Minisink, they burned whole settlements and destroyed the occupants. They killed John Rush. They killed his wife, his son and daughter. They killed seventeen Vanakens and Vancamps. They pursued people on the river and killed them in their boats. They killed Hans Vanfleara and co-working space amsterdam Lambert Brink, Piercewell Goulding and Matthew Rue. They could not, however, kill their way backward through time. They never would regain the Minisink. As we moved along beside the screaming trucks, we were averaging about ten thousand years per step. The progression was not uniform, of course. There might be two million years in one fossil streambed, and then the next lamination in the rock would record a single season, or a single storm-on one flaky surface, a single drop of rain. We looked above our heads at the projecting underside of a layer of sandstone patterned with polygons, impressions made as the sand came pouring down in storm-flood waters over mud cracks that had baked in the sun. From a layer of conglomerate, Anita removed a pebble with the pick end of her rock hammer. “Milky quartz,” she said. “Bull quartz. We saw this rock back up the road in the Precambrian highlands. When the Taconic Orogeny came, it lifted the older rock, and erosion turned it into pebbles and sand, which is what is here in this conglomerate. It’s an example of how the whole Appalachian system continually fed upon co-working space eindhoven itself. These are Precambrian pebbles, in Silurian rock. You’ll see Silurian pebbles in Devonian rock, Devonian pebbles in Mississippian rock. Geology repeats itself.” Now and again, we came to small numbers that had been painted long ago on the outcrops. Anita said she had painted the numbers when she and Jack Epstein were working on the geology of the Water Gap.

Mountainside

Gerelateerde afbeelding

There were fifteen hundred in the Survey, and the quality of their work, their capacity for visualizing plunging synclines and recumbent folds, tended to vary. She looked upon some of them as “losers.” Such people were sent to what she privately described as “penal quadrangles”: the lesser bayous of Louisiana, the Okefenokee Swamp. If they did not know strike from dip, they could go where they would encounter neither. She did not feel pity. Better to be a loser in the United States, she thought, than to be a geological peasant in China. There are four hundred thousand people in the Chinese Geological Survey. “It’s a hell of an outfit,” in Anita’s words. “If they want to see exposed rock, they don’t depend on streambanks and roadcuts, as we do. If an important Chinese geologist wants to see a section of rock, the peasants dig out a mountainside.” She was a map editor for seven years, during all of which she flexplek huren amsterdam continued her conodont research, almost wholly on her own time. Collecting rock from Maryland and Pennsylvania, she crushed it and “ran the samples” at home. Running samples was not just a matter of pushing slides past the nose of a microscope. After pulverizing the rock and dissolving most of it in acid, she had to sort its remaining components, and this could not be done chemically, so it had to be done physically. It was a problem analogous to the separation of uranium isotopes, which in the early nineteen-forties had brought any number of physicists to a halt. It was also something like sluicing gold, but you could not see the gold. Anita primarily uses tetrabromoethane, an extremely heavy and extremely toxic fluid that costs three hundred dollars a gallon. Granite will float in tetrabromoethane. Quartz will float in tetrabromoethane. Conodonts sink without a bubble. Her hands in rubber gloves within a chemical hood, she pours the undissolved rock residue into the tetrabromoethane. The lighter materials, floating, are removed. Inconveniently, conodonts are not all that sink. Pyrite, among other things, sinks, too. With methylene iodide, a fluid even heavier than tetrabromoethane, she turns flexplek huren eindhoven the process around. In methylene iodide, the pyrite and whatnot go to the bottom, while the conodonts, among other things, float. Electromagnetically, she further concentrates the conodonts.

Glacial crevasses

Gerelateerde afbeelding

Where debris had been concentrated in glacial crevasses, melting ice left hillocks, monticles, hummocks, knolls, braes-collections of lumpy hills known generically to the Scots as kames. In Indiana as in Scotland-in La Bresse and Estonia as in New England and Quebec-the sort of country left behind after all these features have been created is known as kame-and-kettle topography. The interstate was waltzing with the glacier-now on the outwash plain, now on moraine, among the kettles and kames of Scottish Indiana. Roadcuts were green with vetch covering glacial till. We left 80 for a time, the closer to inspect the rough country. The glacier had been away from Indiana some twelve thousand years. There were many beds of  flexplek huren arnhem dried-up lakes, filled with forest. In the Boundary Waters Area of northern Minnesota, the ice went back ten thousand years ago, possibly less, and most of the lakes it left behind are still there. The Boundary Waters Area is the scene of a contemporary conservation battle over the use and fate of the lakes. “Another five thousand years and there won’t be much to fight about,” Anita said, with a shrug and a smile. “Most of those Minnesota lakes will probably be as dry as these in Indiana.” Some of the larger and deeper ones endure. We made our way around the shores of Lake James, Bingham Lake, Lake of the Woods, Loon Lake. Like Walden Pond, in Massachusetts, they were kettles. The woods around them were bestrewn with boulders, each an alien, a few quite large. If a boulder rests above bedrock of another type, it has obviously been carried some distance and is known as an erratic. In Alaska, I have come upon glacial erratics as big as office buildings, with soil developing on their tops and trees growing out of them like hair. In Pokagon State Park, Indiana, handsome buildings looked out on Lake James-fieldstone structures, red and gray, made of Canadian rocks. The red jasper conglomerates were from the north shore of Lake Huron. The banded gray gneisses were from central Ontario. The sources of flexplek huren den haag smaller items brought to Indiana by the ice sheets have been less easy to trace-for example, diamonds and gold. During the Great Depression, one way to survive in Indiana was to become a pick-and-shovel miner and earn as much as five dollars a day panning gold from glacial drift-as all glacial deposits, sorted and unsorted, are collectively called. There were no nuggets, nothing much heavier than a quarter of an ounce. But the drift could be fairly rich in fine gold.

Four thousand miles

Afbeeldingsresultaat voor site:ilocate.nl

Interspersed among the uplifted Andes are four thousand miles of volcanoes. The Pacific Ocean floor, going down to melt below that edge of the continent, has done much to help lift it twenty thousand feet. Seafloor-ocean crust-is dense enough to go down a trench, but continents are too light, too buoyant. When a continent comes into a trench, it will become stuck there, causing havoc. Even if part of it goes down some dozens of kilometres, it will eventually get stuck. Australia is such a continent, and where it has jammed a trench it has buckled up the earth to make the mountains of New Guinea, sixteen thousand five hundred feet. When two continental masses happen to move on a collision course, they gradually close out the sea between flexplek huren amsterdam them-barging over trenches, shutting them off-and when they hit they drive their leading edges together as a high and sutured welt, resulting in a new and larger continental mass. The Urals are such a welt. So is the Himalaya. The Himalaya is the crowning achievement of the IndoAustralian Plate. India, in the Oligocene, crashed head on into Tibet, hit so hard that it not only folded and buckled the plate boundaries but also plowed in under the newly created Tibetan Plateau and drove the Himalaya five and a half miles into the sky. The mountains are in some trouble. India has not stopped pushing them, and they are still going up. Their height and volume are already so great they are beginning to melt in their own self-generated radioactive heat. When the climbers in i953 planted their flags on the highest mountain, they set them in snow over the flexplek huren eindhoven skeletons of creatures that had lived in the warm clear ocean that India, moving north, blanked out. Possibly as much as twenty thousand feet below the seafloor, the skeletal remains had formed into rock. This one fact is a treatise in itself on the movements of the surface of the earth. If by some fiat I had to restrict all this writing to one sentence, this is the one I would choose: The summit of Mt. Everest is marine limestone. Plates grow, shrink, combine, disappear, their number changing through time. They shift direction. Before the Pliocene, there was a trench off California. Seafloor moved into it from the west and dived eastward into the earth. Big volcanoes came up.

Complexity

Gerelateerde afbeelding

Deffeyes mused his way along the cut. “There is complexity here because you have not only the upper and lower plates of the Golconda Thrust, which happened in the early Triassic; you also have basin-range faulting scarcely a hundred yards away-enormously complicating the regional picture. If you look at a geologic map of western Canada and Alaska, you can see the distinct bands of terrane that successively attached themselves to the continent. Here the zakelijke energie pattern has been all broken up and obscured by the block faulting of the Basin and Range, not to mention the great outpouring of Oligocene welded tuff. So this place is a handsome mess. If you ever want to study this sort of collision more straightforwardly, go to the Alps, where you had a continent-tocontinent collision and that was it.”
So much for theory. This roadcut contained both extremities of Deffeyes’ wide interests in geology, and his attention was now drawn to a large gap in the sandstone, faulted open probably six or seven million years ago and now filled with rock crumbs, as if a bomb had gone off there in the ground. The material was gradated outward from a very obvious core. In a country full of living hot springs, this was a dead one. Sectioned by the road builders, it remembered in its swirls and convolutions the commotion of water raging hot in rock. The dead hot spring had developed cracks, and they had been filled in by a couple of generations of calcite veins. Deffeyes was zakelijke energie vergelijken busy with his hammer, pinging, chipping samples of the calcite. “This stuff is too handsome to leave out here,” he said, filling a canvas bag. “There was a lot of thermal action here. Most of this material is not even respectable rock anymore. It’s like soil. In i903, a mining geologist named Waldemar Lindgren found cinnabar in crud like this at Steamboat, near Reno. Cinnabar is mercury sulphide. He also found cinnabar in the fissures through which water had come up from deep in the crust. He thought, Aha! Mercury deposits are hot-spring deposits! And he applied that idea to ore deposits generally. He started classifying them according to the temperature of the water from which they were deposited-warm, hot, hotter, and so on. We know now that not all metal deposits are hydrothermal in origin, but more than half of them are.

The impression

Afbeeldingsresultaat voor site:ilocate.nl

On us who saw these phenomena for the first time, the impression made will not easily be forgotten. The palpable evidence presented to us, of one of the most extraordinary and important facts in the natural history of the earth, gave a reality and substance to those theoretical speculations, which, however probable, had never till now been directly authenticated by the testimony of the senses. We often said to ourselves, What clearer evidence could we have had of the different formation of these rocks, and of the long interval which separated their formation, had we actually seen them emerging from the bosom of the deep? We felt zakelijke energie ourselves necessarily carried back to the time when the schistus on which we stood was yet at the bottom of the sea, and when the sandstone before us was only beginning to be deposited, in the shape of sand or mud, from the waters of a superincumbent ocean. An epocha still more remote presented itself, when even the most ancient of these rocks, instead of standing upright in vertical beds, lay in horizontal planes at the bottom of the sea, and was not yet disturbed
by that immeasurable force which has burst asunder the solid pavement of the globe. Revolutions still more remote appeared in the distance of this extraordinary perspective. The mind seemed to grow giddy by looking so far into the abyss of time.
Hutton had told the Royal Society that it was his purpose to “form some estimate with regard to the time the globe of this Earth has existed.” But after Jedburgh and Siccar Point what estimate could there be? “The world zakelijke energie vergelijken which we inhabit is composed of the materials not of the earth which was the immediate predecessor of the present but of the earth which …h ad preceded the land that was above the surface of the sea while our present land was yet beneath the water of the ocean,” he wrote. “Here are three distinct successive periods of existence, and each of these is, in our measurement of time, a thing of indefinite duration. . . . The result, therefore, of this physical inquiry is, that we find no vestige of a beginning, no prospect of an end.”

Salty season

Gerelateerde afbeelding

Only my heels, rump, and shoulder blades seemed to be wet. I rolled over and crawled. I could all but crawl on my hands and knees. And this was June, at the south end-the least salty season, the least salty place in the whole of the Great Salt Lake. Rolling up on one side, and propped on an elbow, I could see the Promontory Mountains across the water to the north, an apparent island but actually a peninsula, reaching southward into the lake. In i86g, a golden spike was carried into the Promontories and driven into a tie there to symbolize the completion of the first railroad to cross the North American continent-exactly one century before the first footprint on the moon, a span of time during which Salt Lake City and Reno would move zakelijke energie apart by one human stride. In that time, also, the railroad twice became dissatisfied with the local arrange
Book 1: Basin and Range ments of its roadbed-losing affection for the way of the golden I spike (over the mountains) and building a causeway and wooden trestle across the lake itself, barely touching the Promontory peninsula at its southern tip. In the late nineteen-fifties, the trestle section was replaced by rock. The causeway traverses the lake like a solid breakwater, dividing it into halves. The principal rivers that flow into the Great Salt Lake all feed the southern half. The water on the north side of the causeway is generally a foot dr two lower and considerably saltier than the water on the other side. Evaporate one cupful of Great Salt Lake North and you have upward of a third of a cup of salt. Evaporate a cupful of Great Salt Lake South and you have about a quarter of a cup of salt, or-nonethelJss-eight times as much as from a cup of the ocean. As the lake drew at our bodies, trying to pull fresh water through our skins, it closeq our pores tight and our lips swelled and became slightly numb. The water stung zakelijke energie vergelijken savagely at the slightest scratch and felt bitter as strep in the back of the throat. We filled a bag with eggstones from the bottom, with oolites, the Salt Lake sand. It was by no means ordinary sand-not the small, smoothed-off ruins of mountains, carried down and dumped by rivers. It was sand that had formed in the lake. Just as raindrops are created around motes of dust, oolites form around 1 bits of rock so tiny that in wave-tossed water they will stir up and move. They move, and settle, move, and settle. And while they are Jp in the water calcium carbonate forms around them in layer after layer, building something like a pearl. Slice one in half with a diamond saw and you reveal a perfect bull’s-eye, or, as its namer obviously imagined it, a stone egg, white and yolk-an oolite. Underwater on the Bahama Banks are sweeping oolitic dunes.

Shifting divides

Afbeeldingsresultaat voor site:ilocate.nl

I used to sit in class and listen to the terms come floating down the room like paper airplanes. Geology was called a descriptive science, and with its pitted outwash plains and drowned rivers, its hanging tributaries and starved coastlines, it was nothing if not descriptive. It was a fountain of metaphor-of isostatic adjustments and degraded channels, of angular unconformities and shifting divides, of rootless mountains and bitter lakes. Streams eroded headward, digging from two sides into mountain or hill, avidly struggling toward each other until the divide between them broke down, and the two rivers that did the breaking now became confluent (one yielding to the other, giving up its direction of flow and going the opposite way) to become a single stream. Stream capture. In the Sierra Nevada, the Yuba had captured the Bear. The Macho member of a formation in New Mexico was derived in large part from the solution and collapse of another formation. There was fatigued rock and incompetent rock and inequigranular fabric in rock. If you bent or folded rock, the inside of the curve was zakelijke energie vergelijken in a state of compression, the outside of the curve was under great tension, and somewhere in the middle was the surface of no strain. Thrust fault, reverse fault, normal fault-the two sides were active in every fault. The inclination of a slope on which boulders would stay put was the angle of repose. There seemed, indeed, to be more than a little of the humanities in this subject. Geologists communicated in English; and they could name things in a manner that sent shivers through the bones. They had roof pendants in their discordant batholiths, mosaic conglomerates in desert pavement. There was ultrabasic, deep-ocean, mottled green-and-black rock-or serpentine. There zakelijke energie was the slip face of the barchan dune. In i841, a paleontologist had decided that the big creatures of the Mesozoic were “fearfully great lizards,” and had therefore named them dinosaurs. There were festooned crossbeds and limestone sinks, pillow lavas and petrified trees, incised meanders and defeated streams. There were dike swarms and slickensides, explosion pits, volcanic bombs. Pulsating glaciers. Hogbacks. Radiolarian ooze. There was almost enough resonance in some terms to stir the adolescent groin.

‘Wil je echt weten wie je bent?’

Afbeeldingsresultaat voor site:ilocate.nl

‘Wil je echt weten wie je bent?’ zegt het dataïsme. ‘Laat die bergen en musea dan maar zitten. Heb je je DNA al laten onderzoeken? Nee?! Waar wacht je dan nog op? Ga dat als het even kan vandaag nog doen. En zorg dat je grootouders, je ouders, broers en zussen ook hun DNA laten checken, want aan hun informatie kun je ook heel veel hebben. En heb je al gehoord van die draagbare biometrische sensorgadgets die dag en nacht je bloeddruk en hartslag meten? Mooi, ga er dan meteen een kopen, doe hem om en verbind hem met je smartphone. En als je toch aan het winkelen bent, koop dan meteen een mobiele camera met microfoon, neem alles op zakelijke energie wat je doet en zet het online. En laat Google en Facebook al je e-mail lezen, al je chats en berichten volgen en al je likes en je surfgedrag bijhouden. Als je dat doet, kunnen de geweldige algoritmen van het Internet der Dingen je vertellen met wie je moet trouwen, wat voor beroep je moet kiezen en of je een oorlog moet beginnen.’ Maar waar komen die geweldige algoritmen vandaan? Dat is het mysterie van het dataïsme. Net zoals wij God en Zijn plan volgens het christendom niet kunnen doorgronden, kunnen de menselijke hersenen volgens het dataïsme de nieuwe meesteralgoritmen niet doorzien. Momenteel worden de meeste algoritmen natuurlijk geschreven door menselijke hackers. Maar de echt belangrijke algoritmen -zoals het zoekalgoritme van Google – worden ontwikkeld door gigantische teams. Elk lid kent maar één stukje van de puzzel en niemand begrijpt het hele algoritme helemaal. Bovendien komen er met de opkomst van machine learning en kunstmatige neurale netwerken steeds meer algoritmen die zelfstandig evolueren, zichzelf verbeteren en leren van hun fouten. Ze analyseren astronomische hoeveelheden data, veel meer dan een mens ooit zou aankunnen, en leren patronen te herkennen en strategieën toe te passen die de menselijke geest volkomen ontgaan. Het zakelijke energie vergelijken basisalgoritme zal misschien nog ontwikkeld worden door mensen, maar naarmate het groeit, gaat het zijn eigen weg en betreedt het paden waar geen mens ooit is geweest -en waar geen mens ooit zal kunnen komen.