Relative dating laws

Nicolas Steno, William Smith, Georges Cuvier, Alexandre Brongniart, and James Hutton developed the basic rules for the science of stratigraphy.Relative dating uses the principles or laws of stratigraphy to order sequences of rock strata.Playfair later commented that, "the mind seemed to grow giddy by looking so far into the abyss of time." Mc Phee (1998) points out that Hutton removed humans from a specious place in time just as Copernicus had removed humans from a specious position in the universe (p. Hutton gives us three more laws to consider when seeking relative dates for rock layers, one of which, the law of inclusions was described earlier.states any feature that cuts across a rock or sediment must be younger than the rock or sediment through which it cuts.

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Geologists establish the age of rocks in two ways: numerical dating and relative dating.

Numerical dating determines the actual ages of rocks through the study of radioactive decay.

Once Steno recognized that the fossils he was contemplating (sharks teeth and sea shells) were formed in the sediments of oceans he was able to work out the basic rules of stratigraphy.

Steno formalized the laws of superposition, original horizontality, original continuity and inclusions in his publication entitled states that any inclusion is older than the rock that contains it.

Your goal is to study the smooth, parallel layers of rock to learn how the land built up over geologic time.

Now imagine that you come upon a formation like this: What do you think of it? How can you make any conclusions about rock layers that make such a crazy arrangement?

Free 5-day trial Discover how geologists study the layers in sedimentary rock to establish relative age.

Learn how inclusions and unconformities can tell us stories about the geologic past.

Relative dating cannot establish absolute age, but it can establish whether one rock is older or younger than another.

Relative dating requires an extensive knowledge of stratigraphic succession, a fancy term for the way rock strata are built up and changed by geologic processes.

Relative dating not only determines which layers are older or younger, but also gives insight into the paleoenvironments that formed the particular sequence of rock.

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