The builder of a house on a cliff overlooking the ocean should be concerned about what geologic phenomenon

Answer: Weathering and erosion that can be caused by the ocean waves

Explanation: In order to build a house on a cliff, one must be aware of the geological process that undergoes near a coastal areas. The waves from the ocean constantly strikes the base of the cliff, as a result of which weathering and erosion takes place. Thereby, the cliff gets undercut by notch, which in due course of time, becomes weak and the cliff gets collapse and gets eroded into the ocean.

The builder should be aware of the rock types that forms the cliff and it should be strong enough to hold the house.

In addition to that, one must also be aware of the consequences of tsunami and rock fall also, that can harm significantly to the people living on the cliff area.

The builder should be concerned with erosion.