GEOL 1001 Chapter : Geology Chapter 10
Document Summary
Geologic time: the span of time since earth"s formation. Uniformitarianism: physical processes we observe today also operated in the past at roughly the same rates and were responsible for the formation of the geologic features we see in outcrops; the present is the key to the past. Relative age: the age of one feature relative to another. Numerical age: the age of a feature in given years; absolute. Principle of original horizontality: sediments settle out of a fluid in a gravitational field, causing layers to be relatively horizontal. Principle of superposition: each layer of rock must be younger than the one below it, for a layer sediment cannot accumulate unlss there"s something to accumulate on. Principle of cross-cutting relations: if one geologic feature cuts across another, the feature that has been cut is older. Fossil succession: once a fossil species disappears at a horizon in a sequence of strata, it never reappears higher in the sequence.
