What is the best criterion for the relative ages of the rocks in this photograph?
A)The igneous rock is younger because it is on top.
B)The igneous rock is younger because it has baked the adjacent rock.
C)The lower rock is younger because it contains pieces of volcanic rock.
D)The igneous rock is older because it formed at depth.

Question

What is the best criterion for the relative ages of the rocks in this photograph? 
A)The igneous rock is younger because it is on top. 
B)The igneous rock is younger because it has baked the adjacent rock. 
C)The lower rock is younger because it contains pieces of volcanic rock. 
D)The igneous rock is older because it formed at depth.

Quizplus · Accepted Answer

The best criterion for determining the relative age of the rocks in the photograph is the principle of cross-cutting relationships. In this case, the igneous rock has intruded into the pre-existing sedimentary rock and must be younger. Additionally, the baked contacts (known as contact metamorphism) indicate that the heat from the magma altered the adjacent rock, providing further evidence that the igneous rock is younger. Therefore, the correct choice is B, the igneous rock is younger because it has baked the adjacent rock.

What Is the Best Criterion for the Relative Ages of the Rocks