Which example describes a method of relative dating?
A.
examining historical records to determine when a volcano erupted
B.
using radioactive isotopes to calculate the age of a rock
C.
measuring the depth of tree bark
D.
using fossils to determine the oldest rock layer in a canyon
The correct answer is option D. Using fossils to determine the oldest rock layer in a canyon is an example of relative dating. Relative dating is a method used to determine the age of rocks and fossils relative to other rocks and fossils. It does not provide an exact age, but instead establishes a sequence of events and determines which layers are older or younger based on the principles of stratigraphy.
To achieve relative dating using fossils, geologists observe the different types of fossils found in rock layers. Fossils are the preserved remains or traces of organisms from past geological ages. By studying the fossil record, scientists can compare the fossils found in different rock layers and determine the relative ages of those layers.
For example, if a certain type of fossil, let's say a trilobite, is found in a lower rock layer and not in any higher layers, it can be inferred that the trilobite existed and became extinct before the formation of the higher layers of rock. This allows geologists to establish a relative age for those rock layers.
In contrast, options A, B, and C describe other dating techniques. Option A involves examining historical records to determine when a volcano erupted, which is a form of historical dating. Option B refers to using radioactive isotopes to calculate the age of a rock, which is a method of radiometric dating. Option C describes measuring the depth of tree bark, which is not directly related to dating methods but may be used in dendrochronology, a technique used to determine the age of trees and climatic conditions.