Question

Which statements describe geologic gaps? Check all that apply.

Geologic gaps happen when volcanoes erupt.
When no sediment is deposited for a long time, angularities can result.
An unconformity happens when rocks do not follow normal geologic rules.
A geologic gap happens when rock is eroded before sediment is deposited.
An unconformity occurs when a rock layer’s relative age can be determined.

Answer 1

Correct answer: Only this statement applies:

- "A geologic gap happens when rock is eroded before sediment is deposited." — True. A geologic gap (an unconformity) is a missing interval in the rock record caused by erosion or non‑deposition before younger sediments are laid down.

Why the others are incorrect:
- "Geologic gaps happen when volcanoes erupt." — False. Volcanic eruptions produce igneous deposits but do not by themselves define a geologic gap (missing time is due to erosion or non‑deposition).
- "When no sediment is deposited for a long time, angularities can result." — False. Lack of deposition (non‑deposition) produces a gap (disconformity), but angular unconformities require tilting/deformation and erosion of older layers before new deposition.
- "An unconformity happens when rocks do not follow normal geologic rules." — False. An unconformity is a break/missing time in the stratigraphic record, not a violation of geologic principles.
- "An unconformity occurs when a rock layer’s relative age can be determined." — False. Determining relative age is a separate process; an unconformity denotes missing time between layers.