The fourth instalment opens with rare footage of Kavachi, an undersea volcano, erupting. The South Pacific islands are typically volcanic in origin, and those of Hawaii are among the youngest. Kilauea's rivers of lava flow directly into the sea, where they cool rapidly and release steam explosively. Pioneering species such as ōhia lehua colonise new land, putting roots down through the cracks into lava tubes where strange troglobites eke out their existence. In the Galápagos Islands, penguins take advantage of the cool shade of lava tubes to raise their chicks, but predatory Sally Lightfoot crabs lie in wait in the shadows. On the Solomons, megapodes bury their eggs in the warm ash of an active volcano, a natural incubator. Aerial photography of Mauna Kea, the Society Islands, Bora Bora and Rangiroa shows how erosion changes the character of volcanic islands over time. Eventually they sink back into the sea, leaving behind coral atolls and sheltered lagoons. Channels between ocean and lagoon attract feeding manta rays. The region's coral reefs are the richest in the world--the pristine Kingman Reef, a sunken volcano, has over 200 kinds of coral alone. Underwater footage includes giant clams spawning, grey reef sharks hunting needlefish by night and a timelapse sequence of a Triton's trumpet engulfing a crown-of-thorns starfish. Reef fish are also agents of erosion--the bumphead parrotfish chews through coral and excretes it as sand. The final scene shows huge swarms of jellyfish in the marine lakes of Palau, the jewel of Micronesia. This episode is titled Rising Lands on Region 1 DVD.