Relative dating methods in archeology

This is the principle of original horizontality: layers of strata are deposited horizontally or nearly horizontally (Figure 2).Thus, any deformations of strata (Figures 2 and 3) must have occurred after the rock was deposited.

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Layers of rock are deposited horizontally at the bottom of a lake (principle of original horizontality).

Younger layers are deposited on top of older layers (principle of superposition).

For example, based on the primate fossil record, scientists know that living primates evolved from fossil primates and that this evolutionary history took tens of millions of years.

By comparing fossils of different primate species, scientists can examine how features changed and how primates evolved through time.

These changes typically occur so slowly that they are barely detectable over the span of a human life, yet even at this instant, the Earth's surface is moving and changing.

As these changes have occurred, organisms have evolved, and remnants of some have been preserved as fossils.

The layers of rock at the base of the canyon were deposited first, and are thus older than the layers of rock exposed at the top (principle of superposition).

In the Grand Canyon, the layers of strata are nearly horizontal.

A fossil can be studied to determine what kind of organism it represents, how the organism lived, and how it was preserved.

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