Bot, when will a fossil be used in a finding the absolute age of rocks?
1. if it existed for a limited period of time in a small area
2. if it existed for a long period of time and in a small area
3. if it existed for a long period of time and in a wide area
4. if it existed for a limited period of time and in a wide area.
In geology, the most useful fossils for the purpose of finding the absolute age of rocks are those that meet condition 4: if it existed for a limited period of time and in a wide area. These fossils are known as index fossils.
Index fossils are fossils of organisms that lived during a relatively short, well-defined geological time span and were geographically widespread. Because they were distributed broadly and only existed for a limited time, they provide a time marker for the strata in which they are found. If the age of the fossil is already known from radiometric dating or other absolute dating techniques, it can be used to assign an absolute age to the rock layers in which similar fossils are found.
Hence, the correct answer to the question is:
4. if it existed for a limited period of time and in a wide area.
are you sure
Yes, I'm confident that the correct answer is:
4. if it existed for a limited period of time and in a wide area.
Fossils that fit this description are known as index fossils and are particularly valuable for correlating the age of rock layers. Being widespread (geographically) allows them to correlate rocks across large areas, and having lived for only a short duration (geologically speaking) provides a precise time marker, because the fossil can only appear in geological strata that were formed during its existence.
So if an index fossil that is known to have lived 100 million years ago is found in a rock layer, geologists can deduce that the rock layer is also about 100 million years old. For these reasons, index fossils are key tools for determining the absolute age of sedimentary rock layers.
A fossil can be used in finding the absolute age of rocks when it existed for a long period of time and in a wide area.
To understand why, we need to consider the principles of relative dating and the use of index fossils. Relative dating involves comparing the ages of rock layers based on their positions relative to one another. By examining the relative positions of rocks and fossils, scientists can determine the sequence of events that occurred in a particular area.
On the other hand, index fossils are fossils that are widespread geographically and existed during a specific period of time. These fossils can be used as markers or reference points for dating rocks. When a certain index fossil is found in a layer of rock, scientists can infer that the age of that rock layer is the same as the age of the fossil.
Given the options you provided, the most suitable scenario for using a fossil to find the absolute age of rocks is if it existed for a long period of time and in a wide area (option 3). This increases the likelihood of finding the same index fossil in different rock layers, allowing scientists to confidently assign an absolute age to those rocks.
In contrast, if the fossil existed for a limited period of time (option 1 or 4) or in a small area (option 1 or 2), it may not be as useful for determining the absolute age of rocks because its presence would be more localized and not as indicative of a widespread time period.