The Solomon Islands' Guadalcanal features Mount Popomanaseu (2,335 m)—Oceania's 6th highest—with ancient volcanic peaks from subduction 40 million years ago. The island chain's rugged interiors average 1,000 m, with limestone karst and 200 waterfalls. Formed by Solomon Sea plate collision, Kolombangara island's caldera reaches 1,770 m. New Georgia Group's volcanoes like Vella Lavella hit 1,079 m. Coastal fringing reefs drop to 1,000 m deep trenches. This volcanic archipelago includes 6 protected areas with endemic megapodes and 700 coral species across 992 islands.
