Question

Geologists use tools other than the law of superposition to help them with relative dating. Which statements describe those tools? Check all that apply.

An unconformity is created when lava pours out on Earth’s surface.
Faults are the result of volcanic activity.
Intrusions and extrusions are sedimentary formations.
Cross-cutting features are always younger than the surrounding rock.
When material erodes before sediment is deposited on it, a geologic gap results.

Answer 1

Correct choices:
- Cross-cutting features are always younger than the surrounding rock. (True — this is the principle of cross-cutting relationships.)
- When material erodes before sediment is deposited on it, a geologic gap results. (True — this describes an unconformity.)

Why the others are incorrect:
- An unconformity is not created simply by lava pouring out; an unconformity is a gap in the rock record caused by erosion or non-deposition.
- Faults are caused by tectonic stresses (movement of the crust), not specifically by volcanic activity.
- Intrusions and extrusions are igneous, not sedimentary, formations.