How is relative dating used
Any observable tilting or swirling is due to disruption of the process. Material that intrudes or cuts into a horizontal bed is assumed to be younger than the material that is disrupted.
Consider a lake that dries out or somehow contains older sediments that are washed into it.
These sediments are deposited on top of younger sediments currently being deposited in the lake.
The resulting sequence from the bottom-most sediments would be oldest-to- young-to- older.
Adequate age control is thus a limiting factor in studies of active tectonism.
Correlation techniques are locally useful and depend on recognition of an event whose age is known, such as a volcanic eruption or a paleomagnetic reversal.Until this century, relative dating was the only technique for identifying the age of a truly ancient object.By examining the object's relation to layers of deposits in the area, and by comparing the object to others found at the site, archaeologists can estimate when the object arrived at the site.Stratigraphy is the oldest of the relative dating methods that archaeologists use to date things.Stratigraphy is based on the law of superposition--like a layer cake, the lowest layers must have been formed first.
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Geologic studies of active tectonism are greatly aided by definition and time calibration of local stratigraphic sequences.