List events A–F shown in Figure 13-1 in the order that they occurred, beginning with the oldest event.
Answers
Answer:
What method can scientists use to determine the absolute age of a rock?
Disconformities and nonconformities are both types of unconformities. Nonconformities occur where layers of sedimentary rock are deposited over eroded igneous or metamorphic rock. Disconformities occur when there is a gap due to erosion or non-deposition between layers of sedimentary rock.
Suppose that you are a geologist trying to determine the relative age of several rock layers. Unfortunately there are so many unconformities in the area that it is difficult to rely on the principle of superposition. How might you figure out this puzzle?
One way to get extra information that might help you determine the relative ages of these rocks is to examine any fossils contained in the layers. The time period that these fossils appear might be known, and this could help you begin to sort out which rock layers are older than others.
Explain what is meant by correlating rock layers.
Correlating rock layers means matching exposed layers of rock in places that are apart from each other. You try to identify layers of rock in both places and match the sequence of the layers of rock and any fossils in them. If the rock layers correlate, it means they are from the same rock formation and rock between the two locations has eroded.
When did the fault in Figure 13-1 occur?
Between B and A
What is a nonconformity?
A nonconformity occurs where layers of sedimentary rock are deposited over eroded layers of igneous or metamorphic rocks.
Explain the principle of superposition in your own words.
The principle of superposition states that the relative ages of rocks can be determined by their positions in a rock bed. Older rocks are on the bottom; younger rocks are on the top.
The fossil record shows that some animals, such as the horseshoe crab, have existed unchanged for millions of years. Other organisms, such as pigs, have undergone a well-documented sequences of changes. Which type of organism would be most useful as an index fossil? Explain your answer.
Pigs would be more useful as an index fossil. The well-documented changes that the occurred in the fossil record would help geologists determine the ages of rocks much more than the unchanging horseshoe crabs.
If horizontal layers of sedimentary rock have a vertical fault running through them, how might a geologist use relative dating to determine when the fault occurred?
The layers had to be there before the fault could form if the fault ran through the horizontal layers. The relative age of the rocks is older than the relative age of the fault.
List events A-F shown in Figure 13-1 in the order that they occurred, beginning with the oldest event.
F, E, D, C, B, A
What is an unconformity?
An unconformity is an area where the rock layers do not line up. These are caused by erosion or periods without any deposition.