ENVIRSC 1G03 Lecture Notes - Lecture 8: Unconformity, Stratigraphic Column, Geologic Time Scale
2 Oct 2017
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10. 1 intro: geologic time - span of time since earth"s formation, tools used to determine numerical age of earth and features in years: 10. 3 geologic principles for defining relative age: principle of uniformitarianism - states that physical processes we observe today, also operated in the past at roughly comparable rates. Present is key to past: principle of original horizontality - states that layers of sediment when first deposited are fairly horizontal as sediments accumulate in low relief in a gravitational field. Top youngest, bottom oldest: principle of lateral continuity - states that sediments generally accumulate in continuous sheets within a given region. Extinction is forever: this observation is repeated in million locations all over the world. Index fossils (guide fossils) - some fossil species are widespread but survived for a relatively short interval of geologic time: they can be used by geologists to associate strata with the specific time interval.
