Which statement explains one reason why unconformities occur? O Rocks along a fault break and move.
O Igneous rock forms at Earth's surface.
O No sediment is deposited over a long time.
O Igneous rock forms between sedimentary layers.

Here, we are required identify which statement best explains one reason why Unconformities occur.

The statement which explains one reason why Unconformities occur is the third choice: i.e

No sediment is deposited over a long time

Unconformities can also be referred to as geologic gap.

Unconformity is a situation characterized by "no sediment is deposited over a long time". Unconformity refers to an opening between rocks or mountains. The opening is caused by the effect of water erosion.

The criteria for the occurrence of Unconformities include:

A geologic gap is synonymously known as pass or saddle.

Therefore, the statement which best fits a reason why unconformities occur is "No sediment is deposited over a long time".

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b is the right answer for this question.