Question

read the passage and answer the following question(s).
dating rock strata
scientists can determine the age of rock layers by measuring radioactive elements within the rock. radioactive elements found in sedimentary rocks decay quickly, so this method can only date sedimentary rocks that are less than 50,000 years old. volcanic rock contains radioactive elements that decay very slowly, so scientists can date volcanic rocks that are much older than 50,000 years.
a team of scientists is investigating a rock formation found in a region. the diagram shows the rock formation that the scientists are investigating.
how old are the fossils in layer 5?
a. between 400 and 550 million years old
b. between 240 and 400 million years old
c. younger than 240 million years old
d. older than 550 million years old

Explanation:

According to the diagram, Layer 5 is a sedimentary rock layer. The adjacent volcanic rock layers (Layer 2 is 550 million years old and Layer 6 is 400 million years old). Since sedimentary rock layers form between volcanic events (in this context of rock - strata dating), the fossils in Layer 5 must be between the ages of the adjacent volcanic layers.

Answer:

B. between 400 and 550 million years old