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STRANGE SYMBIOSIS* E. LLOYD DU BRUU The ice was here, the ice was there, The ice was all around: It cracked and growled, and roared and howled, Like voices in a swound! [Coleridge] Four times in the last million years monstrous masses of ice slid down in major surges over the face of the earth and as many times receded, advanced, and retreated in an indecision that polished and scraped the rocky substratum. During these desolate times a cold cloak covered more than a quarter of all the land. And we are still in a glacial age. Ice persists in Alaska, Greenland, Scandinavia, and Siberia. It tops the peaks of New Zealand and the Andes, the Himalayas and the Alps. The bleak, rigid, blue look of glaciers makes them seem immutable, hard and brittle, permanent. But they are really weak, plastic rocks flowing slowly forward, yielding under the shear stress of tremendous weight. The Alpine complex has been the most extensively studied of these glacial systems; the glacial ages were first defined from the peculiar structuration of its northern slope. But the strange terrain along its western edge hoards a hidden enticement which will slowly be brought into view. It was here, at the foot of the Rhone Valley Glacier , that the tenacious reluctance of naturalist Agassiz finally succumbed to the wondrous magnitude of glacial mechanism. He saw the transported blocks of rock, the burnished and engraved bedrock, the "living" glacier. He became the transported convert, the most insistent protagonist of the notion of worldwide glaciation. Let's look backward at this land to the west of the Alps. In Paleo- * This paper was read at the annual ladies' night celebration of the Chicago Literary Club, May 22, 1972. The paper is reprinted with the permission of the club. t Professor of anatomy, Colleges of Medicine and Dentistry, University of Illinois, Chicago 60680. 558 I E. Lloyd Du Bruì · Strange Symbiosis zoic times—some 500,000,000 years before the ornamental icing—most of Europe was submerged. The weight of the covering water, in part, produced a corrugated buckling of the earth's crust beneath. This raised above the sea's surface a large, V-shaped, mass of land. Its western arm ran southeast, down from Brittany; its eastern arm ran southwest, down from Ardennes and Vosges. Both met in the Massif Central, ending near what would become the northern coast of the Mediterranean Sea. But nothing is eternal. In Mesozoic times—beginning some 200,000 ,000 years back—the usual erosional processes denuded the contours of this young land. Gradually it submerged, retiring modestly beneath the surface to clothe itself with a heavy coat of calcareous marine debris. In Cenozoic times—some 50,000,000 years back—land once more emerged and its distinctive outline became more sharply defined. The land would become France as it got caught in the squeeze between the Alps and the Pyrenees. These later buckling upthrusts had an extraordinary effect on the sculpturing of the terrain between. Above, the notch of the V became the container of the broad Parisian Basin. Below, lateral and parallel to each arm of the land, gutters of sea were formed by dikes rising as their opposite shores—Pyrenees to the west, Alps to the east. The long, narrow gutter along the east was the Rhone Basin. A flaw in the shore of the eastern arm of land allowed a flow from the Parisian Basin into the Rhone Basin. And this sluiceway, opening into the hollow between Alps and Massif Central, has been called Seuil de Bourgogne, the Burgundian Gateway . The land continued to lift, which slid the sea off to the south. And so it is that today an undeviating groove, gouged in the Jurassic and Cretaceous bedrock, runs through two-thirds the length of the land of France. From far to the north, walled on the east by the steep, west slope of the Vosges Mountains, it channels straight south through the primeval Burgundian Gateway to the marshy Camargue on the coast of the Mediterranean Sea. Once again the perpetual erosion burnished the highland tops and brushed the debris down into the hollow below. The long alluvial...

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Additional Information

ISSN
1529-8795
Print ISSN
0031-5982
Pages
pp. 558-577
Launched on MUSE
2015-01-07
Open Access
No
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