Cross cutting relationships relative dating

Posted by / 06-Nov-2014 15:19

Cross cutting relationships relative dating

Long before geologists tried to quantify the age of the Earth they developed techniques to determine which geologic events preceded another, what are termed "relative age” relationships.These techniques were first articulated by Nicolas Steno, a Dane living in the Medici court of Italy in the 17th C.Relative time places events or formations in order based on their position within the rock record relative to one another using six principles of relative dating.Relative time can not determine the actual year a material was deposited or how long deposition lasted; it simply tell us which events came first.Unlike relative time, absolute time assigns specific ages to events or formations and is typically recorded in years before present.This means that a quartz sandstone deposited 500 million years ago will look very similar to a quartz sandstone deposited 50 years ago.Making this processes even more difficult is the fact that due to plate tectonics some rock layers have been uplifted into mountains and eroded while others have subsided to form basins and be buried by younger sediments.

This process lead to a system of time containing eons, eras, periods, and epochs all determined by their position in the rock record.For example, rocks of the Phanerozoic eon are found on top of rocks from the Proterozoic eons therefore rocks of the Phanerozoic are younger than rocks of the Proterozoic.With out individual time stamps the process of dating these structures could become extremely difficult.To deal with many of these problems geologists utilize two types of geologic time: relative time and absolute time.The most obvious feature of sedimentary rock is its layering.

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This feature is produced by changes in deposition over time.