What term refers to large boulders piled up on the beach to protect shorelines?

The term that describes large boulders piled up on the beach to protect shorelines is rip rap. Rip rap is used in coastal engineering to prevent erosion and stabilize the shoreline. These large rocks or boulders are strategically placed to absorb and deflect wave energy, thus mitigating the impact of storms and high tides on the coast. This practice helps to maintain the integrity of the beach and surrounding land.

Other terms related to coastal geography, such as beach, spit, and reclamation, refer to different aspects of coastal environments or land use. A beach is the collection of sand or pebbles along the shore, while a spit is a narrow point of land projecting into a body of water, formed by sediment deposition. Reclamation involves creating new land from water bodies, typically using soil or sand, and is not specifically about erosion protection. Thus, rip rap is the specific term that accurately describes the protective boulders on the beach.