GEO 110 Chapter 12: Chapter 12
24 Dec 2017
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The pace of change: this guiding principle of earth science, called uniformitarianism, presupposes that the same physical processes now active in the environment were operating throughout. Ea(cid:396)th"s histo(cid:396)(cid:455: the ph(cid:396)ase (cid:862)the p(cid:396)ese(cid:374)t is the ke(cid:455) to the past(cid:863) des(cid:272)(cid:396)i(cid:271)es the p(cid:396)i(cid:374)(cid:272)iple. Fo(cid:396) e(cid:454)a(cid:373)ple, the processes by which streams carve valleys at present are assumed to be the same as those that carved valleys 500 million years ago. Evidence from the geologic record, preserved in layers of rock that formed over millennia, supports this concept, which was first hypothesized by geologist james hutton in the 18th century and later amplified by. Examples are the six major extinctions of life forms in. The horizontally arranged rock layers of the grand can- yon and many other canyons of the. U. s. southwest are an example: the scientific study of these sequences is stratigraphy. Important time clues for example, fossils, the remains of ancient plants and animals lie embedded within these strata.
