Question

a geologist is studying a geologic cross section of rock layers in a national park. the rock layers appear to be well preserved and undisturbed. which statement best identifies the oldest rock layer in the cross section?\
\
\bigcirc the oldest rock layer is above the middle layer of the cross section.\
\bigcirc the oldest rock layer is above the bottom layer of the cross section.\
\bigcirc the oldest rock layer is the bottom layer of the cross section.\
\bigcirc the oldest rock layer is the top layer of the cross section.

Explanation:

In geology (a subfield of Natural Science, specifically related to Earth's rock layers), the principle of superposition states that in undisturbed rock layers, the oldest layers are at the bottom and younger layers are deposited on top. Since the rock layers here are well - preserved and undisturbed, the oldest rock layer should be the bottom layer of the cross - section. The first option says the oldest is above the middle, which is wrong. The third option says the oldest is above the bottom, which is wrong. The fourth option says the oldest is the top layer, which is wrong. Only the second option, "The oldest rock layer is the bottom layer of the cross section", follows the principle of superposition.

Answer:

The oldest rock layer is the bottom layer of the cross section. (The option with this statement, assuming the options are labeled as: The second option among the given ones, e.g., if the options are A. The oldest rock layer is above the middle layer of the cross section. B. The oldest rock layer is the bottom layer of the cross section. C. The oldest rock layer is above the bottom layer of the cross section. D. The oldest rock layer is the top layer of the cross section. Then the answer is B. The oldest rock layer is the bottom layer of the cross section.)