Question

activity 1 of 3
geologic cross sections give scientists information about the geologic
history of an area. use the geologic cross section below to answer
the following questions.
use the diagram to select the one true statement about the rock layers.
a. a occurred after d.
b. c is younger than b.
c. c occurred before d.
d. a is older than b.

Explanation:

• Option A: A is a sedimentary layer and D is a fault/intrusion. Since D cuts through A, A occurred before D. So this option is false.
• Option B: C is a fault/intrusion. B is a sedimentary layer. C cuts through B, so C is younger than B. This option is false.
• Option C: C is a fault/intrusion. D is also a fault/intrusion. C cuts through D, so C occurred after D. This option is false.
• Option D: A is a sedimentary layer. B is a sedimentary layer. In sedimentary rock layers, the lower layer (B) is older than the upper layer (A). So this option is true.

Answer:

D. A is older than B.