The first practical large-scale application of stratigraphy was by William Smith in the s and early 19th century. The third-longest phase of geologic time, after an era; it is equivalent to a system in the stratigraphic time scale. The Shaping of Our World. Penguin Reference, London, p. Many absolute dating techniques take advantage of radioactive decaywhereby a radioactive form of an element is converted into a non-radioactive product at a regular rate. His two-volume work, Modern Lithogenesis ;was a watershed for modern research with sedimentary facies. Chronostratigraphy also uses six time units:
Sediment accumulates and then, as a result of plate movement, is moved about and eventually experiences weathering and erosion.
Biologic stratigraphy was based on William Smith's principle of faunal successionwhich predated, and was one of the first and most powerful lines of evidence for, biological evolution. Wikimedia Commons has media related to Category: Sites often contain strata that have been disturbed by natural processes, such as floods, and human activities, such as digging. The Cambridge Companion to Historical Archeology. During periods of flood, for instance, rivers can drop tons of silt on what had been working farm land, and a single storm can carry away tons of beach sand into the ocean depths. Before the advent of absolute dating methods, nearly all dating was relative. Statistics for stratigraphic Look-up Popularity.