File:Shore processes and shoreline development (1919) (14783850303).jpg

Identifier: shoreprocessessh00john (find matches)
Title: Shore processes and shoreline development
Year: 1919 (1910s)
Authors: Johnson, Douglas Wilson, 1878-1944
Subjects: Shorelines Coasts
Publisher: New York : John Wiley & Sons, Inc. (etc., etc.)
Contributing Library: University of California Libraries
Digitizing Sponsor: MSN

View Book Page: Book Viewer
About This Book: Catalog Entry
View All Images: All Images From Book
Click here to view book online to see this illustration in context in a browseable online version of this book.

Text Appearing Before Image:
e seriesof berraces (Fig. 38), the highest of which is over 1500 feet abovesealevel. There can be no doubt that had all this erosive workbeen performed at one horizon the resulting platform wouldhave been much broader than any one of the existing wave-cutsurfaces. Comparatively weak waves on Lake Michigan attack-ing shores of glacial drift have formed a terrace whose outermargin is approximately 60 feet below the lake surface, andwhich varies in breadth from 2 to 6 miles, with a maximum at onelocality of 12 miles. Andrews^^ assumed that the entire breadthof the terrace was due to wave erosion; and proceeding on thefurther assumption that the rate of wave erosion is the sameduring all stages of terrace cutting, he used the breadth of the ter-race and the present known rate of cliff retreat to establish ameasurement of post-glacial time. Both his assumptions mustbe considered erroneous; but it seems probable that from one toseveral miles of the terrace breadth is wave-cut, even though a
Text Appearing After Image:
(229) 230 DEVELOPMENT OF THE SHORE PROFILE large part of it represents the effect of wave deposition. In apaper entitled Fenomeni di abrasione sulle coste dei paesi dellAtlante -^ Fischer describes a submarine terrace bordering partsof the north coast of Africa having an outer margin approxi-mately 100 to 200 meters below the surface of the Mediter-ranean, and a maximum breadth of at least 12 miles. The en-tire breadth of this terrace is regarded bj^ Fischer as a marineabrasion platform; but it seems probable that the outer partof it is of constructional origin. Good photographic illustrationsof its exposed landward margin, where it is an undoubted plat-form of marine abrasion, accompany the same authors reporton Kiistenstudien und Reiseeindrucke aus Algerien,3o whilea short description of the terrace occurs in an earlier paper on Kiistenstudien aus Nordafrika.^^ It is well known that cer-tain volcanoes formed in the ocean have been reduced by waveerosion to submarine platforms within

Note About Images