Question

which characteristic is shared by intrusions and faults?
all are cracks.
all are igneous rocks.
all cause gaps in the geologic record.
all are younger than surrounding rocks.

Explanation:

1. Analyze Option A: Intrusions are igneous rock formations (not just cracks), while faults are fractures with movement. So not all are cracks. Eliminate A.
2. Analyze Option B: Faults are not igneous rocks (they are fractures in rock), only intrusions can be igneous. Eliminate B.
3. Analyze Option C: Intrusions don't cause gaps in the geologic record (unconformities do), and faults don't directly cause such gaps. Eliminate C.
4. Analyze Option D: Intrusions (igneous rock formed later) and faults (form after the surrounding rock due to tectonic activity) are both younger than the surrounding rocks. This fits.

Answer:

D. All are younger than surrounding rocks.