. Collected reprints, Essa Institute for Oceanography. Oceanography the iceberg analogy. He assumed that continents actively ploughed their way through the mantle like great ships at sea, using forces he called Westwand- erung (westward drift) and Poleflucht- krajt (pole fleeing force). These forces, although real, were shown to be negligibly small and served to dis- credit the continental drift concept for a few decades. A Jigsaw Puzzle The reconstruction of the ancient supercontinents envisioned by conti- nental drifters is a jigsaw puzzle. The jigsaw puzzle player has two clue
. Collected reprints, Essa Institute for Oceanography. Oceanography the iceberg analogy. He assumed that continents actively ploughed their way through the mantle like great ships at sea, using forces he called Westwand- erung (westward drift) and Poleflucht- krajt (pole fleeing force). These forces, although real, were shown to be negligibly small and served to dis- credit the continental drift concept for a few decades. A Jigsaw Puzzle The reconstruction of the ancient supercontinents envisioned by conti- nental drifters is a jigsaw puzzle. The jigsaw puzzle player has two clues: matching the picture, using color, tone or graphics; or fitting, using the shape of the pieces. The continental drift puzzle has the same clues. The "pic- ture" is sketched by the bedrock geolo- gy, the foldbelt trendlines, distribution of glacial formations (tillites), etc. But there are difficulties. The geological picture resembles an impressionistic painting. No two observers seem to agree whether or not any particular assembly is really pictorially in sharp focus. Also full rendering is hindered by the contiguous parts being sub- merged continental shelves which are zones of no picture information, or "white ; Furthermore the prop- er pieces are the continental outlines as delineated by the 1000-fathom line rather than by the shoreline or the shelf edge. Our marine surveys are not sufficiently good as yet to delineate the position of this contour. Following Wegener's lead, many drifters have fitted the continents to- gether by forcing the fit, , by taking. The reconstruction of the ancient supercontinents envisioned by drifters is a jigsaw puzzle. 71. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Institute for Oceanography; Atlantic Oceanographic Laboratories (U. S. );
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