Punalu’u Beach on Hawaii’s Big Island is a steeply shelving pocket beach. It is best known for its dramatic-looking black sand, which is composed of grains of the volcanic rock basalt. The sand has been produced by wave action on local cliffs of black basaltic lava. Punalu’u, in common with about half the land area of Hawaii, lies on the flank of Mauna Loa, the world’s most massive volcano. Lava produced by the volcano dominates the local landscape—although no lava has reached Punalu’u from Mauna Loa or the nearby active volcano Kilauea for several hundred years.
The beach is a popular location for swimming and snorkeling, but underwater springs that eject cold water into the sea close to the beach can cause discomfort. Punalu’u Beach is also visited by green turtles, which come to eat seaweed off rocks at the edge of the beach and bask on the warm, heat-absorbing sand.