After the mountains it lifted had been largely eroded away, their stubs and their detritus, much of which had turned into sedimentary rock, became involved in the Acadian Orogeny; and when the Acadian Orogeny was long gone by, its mountain stubs and lithified debris were caught up in the Alleghenian Orogeny, which drove into the sky still another massif, the ruins of which lay all about us now. In such manner had each of the orogenies of the Appalachians cannibalized the products of previous pulses, and now we were left with this old mountain range, by weather almost wholly destroyed, but nonetheless flexplek huren amsterdam zuidas containing in a traceable and unarguable way the rock of its ancestral mountains. She said the Delaware Water Gap, with its hard quartzites, represented action from the heart of the story, debris from the Taconic Orogeny: boulders, pebbles, sands, and silts carried down from bald mountains by the rapids of big braided rivers-a runoff unimpeded by vegetation, when not so much as one green leaf existed in the terrestrial world. Long before the Taconic mountain-building pulse was felt, the scene was very different. A subdued continent, consisting of what is now the basement rock of North America, stood low with quiet streams, collecting on its margins clean accumulations of sand. One can infer the flat landscape, the slow rivers, the white beaches, in the rock that remains from those Cambrian sands. Sea level, never constant, moved generally upward all through Cambrian time. The flexplek huren hilversum water advanced upon the continent at an average rate of ten miles every million years, spreading across the craton successive coastal sands. Potsdam sandstone. Antietam sandstone. Waynesboro sand stone. Eau Claire sandstone. There were fifty-four million years in the long tectonic quiet of Cambrian time, 544 to 490 million years before the present. By the end of the Cambrian and the beginning of the Ordovician, the ocean had spread its great bays upon the continents to an extent that has not been equalled in five hundred million years, with the possible exception of the highest Cretaceous seas. No one knows why. There is a fixed amount of water in the world. It can rain and run, evaporate, freeze, sit in deep cold pools on abyssal plains, but it cannot leave the earth. When large amounts of it collect as ice upon the continents, the level of the sea drastically goes down. In much of Cambra-Ordovician time, glaciation was absent from the world, and almost all water was in a fluid state. But that alone will not explain the signal height of the sea. In most of the known history of the earth, glacial ice has actually been insignificant.