The specific events within Earth history are discussed in Chapter 8. Using this time scale, geologists can place all events of Earth history in order without ever knowing their numerical ages. The figure of this geologic time scale shows the names of the units and subunits. Eventually he produced the first national geologic map of Britain, becoming known as “the Father of English Geology.” Nineteenth-century scientists developed a relative time scale using Steno’s principles, with names derived from the characteristics of the rocks in those areas. William Smith (1769-1839), working with the strata of English coal mines, noticed that strata and their sequence were consistent throughout the region. Nicolas Steno (1638-1686) introduced basic principles of stratigraphy, the study of layered rocks, in 1669. Working out Earth’s history depended on realizing some key principles of relative time. The geologic time scale and basic outline of Earth’s history were worked out long before we had any scientific means of assigning numerical age units, like years, to events of Earth history. Explain the relationship between time units and corresponding rock units-chronostratigraphy versus lithostratigraphy.
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