A staggering sea scene

The sharp-edged sea stacks of Pegadung speak to an intense tectonic history here on Sumatra, the largest island within Indonesia and one of Earth's most volcanic places. Its mountainous spine still includes nearly 70 active volcanoes, stretching more than a thousand miles from the Strait of Malacca in the north to these craggy shores in the south. Rivaling the massive isle's wild geology is its biology: Sumatra boasts unique types of elephant, rhinoceros, tiger, and orangutan.