BSC 2010 Chapter Notes - Chapter 18: Igneous Rock, Radiometric Dating, Continental Drift
10 Apr 2017
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Chapter 18 the history of life on earth. Concept 18. 1 events in earth"s history can be dated. To understand long-term patterns of evolutionary change, we must not only thin in time scales spanning many millions of years, but also consider events and conditions very different from those we observe today. We cannot tell the ages of rocks just by looking at them, but we can visually determine the ages of rocks relative to one another. Geologists combined steno"s insight with their observations of fossils contained in sedimentary rocks. Fossils of similar organisms are found in widely separated placed on earth. Certain fossils are always found in younger strata, and certain other fossils are always found in older strata. Organisms found in younger strata are more similar to modern organisms than are those found in older strata. These patterns revealed a lot about the relative ages of sedimentary rocks and the fossils they contain.
