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Answer:
4.index fossils, intrusions, and cross-cutting relationships
Explanation:
There are various geologic features or phenomenon that determines the relative ages of rocks . This geologic features or events includes index fossils , intrusions, cross cutting relationship etc. Note relative ages of rock does not give the actual ages oft the rocks but instead compares the ages of these rocks. Knowing the relative ages of rocks, one can decipher which rock is older or which one is younger. The geologic features give details on the sequence of event that happens through the formation.
Like the principle of cross cutting relationship states that the geologic feature which cut across or intrudes another geologic feature is younger than it surrounding rock.
Index fossils are remains of organisms that are widely spread. The deposition of this remains can give the sequence for deposition of the surrounding rocks which these fossils are found.
Intrusions occurs when geologic features like plutons invades another rock body. Geologically, the plutons will be younger than the surrounding or host rock.
The correct list of three different geologic features that help scientists determine the relative ages of rocks by their position is option 4, "index fossils, intrusions, and cross-cutting relationships".
Index fossils are used by geologists as clues to determine the age of rocks. These fossils are useful because they contain the remains of certain organisms, which scientists can relate to a specific period in time, thus offering clues as to the age of the rocks that surround them.
Intrusions are when magma dries and forms its own layer above other rocks. Scientists use these as clues as to the age of the other rocks because whenever this happens, we can know that the dried magma is younger than the surrounding rocks.
Finally, cross-cutting relationships are when one form of rock cuts through the layers of other rocks, this follows a geological rule which states that the cross-cutting rock will be younger than the others, offering yet another clue to the age of the rocks.
For these reasons, the correct list of geologic features that help scientists determine the relative ages of rocks by their position is option 4, "index fossils, intrusions, and cross-cutting relationships".
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