How can the relative age of a rock be determined?

Answer 1

Layers that are farther beneath the surface are usually older in relativity to the layers that are closer to the surface.

Geologists look for index fossils, evidences of specific organisms that were widespread, rapidly evolving, plentiful, and only existed during a specific geologic time period. Trilobites are an example of one such index fossil. When an index fossil is identified in a rock layer, it can be assumed that the age of the rock falls within the time period of the organism's existence. This is called relative dating, and is used in field study as a quick reference to the age of a rock stratum.

Answer 2

A sedimentary rock's age can be estimated (relative age) by index fossils that may be present in the rock. Certain fossils only appear in rocks from a certain geologic age. This method is known as 'relative dating' and the age is called the 'relative age'. The 'absolute' geologic age of the strata which bear the index fossils has been determined by the radiometric age of igneous intrusions which are relative to the layers of sedimentary rock, according to the Law of Superposition and the Law of Horizontality. For igneous and metamorphic rock, age is determined primarily by radiometric dating based on decay of isotopes found within the rock. For some igneous rocks, the age of the rock is known precisely from historical records correlating to its formation.

Answer 3

Law of superposition (one that most earth science students remember) - the oldest layer is on the bottom while the youngest layer is the top.

In very heavily folded sedimentary sequences that may have been overturned or at least pushed up past the vertical, also look for "way up" signs on exposed surfaces, such as ripple-marks, turbidity features, trace-fossils and (on the sides of the units) cross-bedding direction.

Answer 4

the bottom layers are old rock or layers and the top layers are new rock or layers

Answer 5

It can be determined by the relative position and depth of its occurrence compared to other horizontally occurring strata and additionally by the types of index fossils it may contain.

Answer 6

They can use either radiometric dating or magnetostratigraphy.

Answer 7

By kissing the rock and eating it