THE PROCESSION OF LIFE THROUGH THE AGES
October 27, 2009 | Posted by maneerat The Rock Record
How do we know when the various classes of animals and plants were established on the earth? How do we know the order of their appearance and the succession of their advances? The answer is: by reading the Rock Record. In the course of time the crust of the earth has been elevated into continents and depressed into ocean-troughs, and the surface of the land has been buckled up into mountain ranges and folded in gentler hills and valleys. The high places of the land have been weathered by air and water in many forms, and the results of the weathering have been borne away by rivers and seas, to be laid down again elsewhere as deposits which eventually formed sandstones, mudstones, and similar sedimentary rocks. Much of the material of the original crust has thus been broken down and worked up again many times over, and if the total thickness of the sedimentary rocks is added up it amounts, according to some geologists, to a total of 67 miles. In most cases, however, only a small part of this thickness is to be seen in one place, for the deposits were usually formed in limited areas at any one time.
Categories: THE OUTLINE OF SCIENCE | 
Tags: Air And Water, Amphibians, Animals And Plants, Continents, Crust Of The Earth, Devonian Period, Fossils, Geologist, Geologists, Hills And Valleys, Mountain Ranges, Plants And Animals, Procession, Sedimentary Rocks, Sediments, Strata, Succession, Troughs, Vicious Circle, Weathering | 
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