Question

What does an unconformity in a sequence of rock layers reveal about geologic history?
• A rock layer must have turned upside down.
• A layer of rock might have eroded.
• The layers must have been deposited very quickly.
• The layers must cover hundreds of square miles.

Answer 1

An unconformity in a sequence of rock layers typically indicates that a layer of rock might have eroded. An unconformity represents a gap in the geologic record, where rock layers were either not deposited for a period of time or were eroded away before deposition resumed. This suggests a significant interruption in the geological timeline, which can reveal information about past geological events, such as periods of erosion or non-deposition.