When a scientist finds a section of rock that has lots of different strata, he assumes that the bottom-most layer is the oldest, and the top-most layer is the youngest.
But sometimes, a scientist finds a couple of rock outcrops that are separated by a wide distance.
Dating techniques are procedures used by scientists to determine the age of an object or a series of events.
This method is based on the assumption (which nearly always holds true) that deeper layers of rock were deposited earlier in Earth's history, and thus are older than more shallow layers.
The successive layers of rock represent successive intervals of time.
In archaeological terminology, there are two categories of dating methods: absolute and relative.
Absolute dating utilizes one or more of a variety of chronometric techniques to produce a computed numerical age, typically with a standard error.
In Assignment 3, we began exploring the age of the Earth. Through presentation and discussion of individual ideas, the class reached agreements as to the best way to complete each of the prompts.
You worked in small groups and as a class to complete the "If Scientists Think. Today's assignment will allow you to compare and contrast your ideas to some of the actual methods scientists used to develop an estimation of the age of the Earth.
Since certain species of animals existed on Earth at specific times in history, the fossils or remains of such animals embedded within those successive layers of rock also help scientists determine the age of the layers.
Similarly, pollen grains released by seed-bearing plants became fossilized in rock layers.
Before the advent of absolute dating methods in the twentieth century, nearly all dating was relative.
The main relative dating method is stratigraphy (pronounced stra-TI-gra-fee), which is the study of layers of rocks or the objects embedded within those layers.
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