What geographical feature is found on Oahu that separates the island from the Pacific Ocean?

The geographical feature that separates Oahu from the Pacific Ocean is mountains. Oahu is characterized by a rugged landscape, with several mountain ranges that contribute to its natural beauty. The Ko'olau and Waianae mountain ranges are prominent on the island, forming a barrier that significantly influences the island's climate and ecosystem.

These mountains create a rain shadow effect, where the windward side receives abundant rainfall, fostering lush vegetation, while the leeward side tends to be drier. This distinct topography also plays a role in the formation of various microclimates across the island. Unlike rivers, valleys, or beaches, which are more associated with water features or lowlands, the mountains of Oahu effectively act as a divider between the island's inland areas and the vast Pacific Ocean beyond.