Krakatoa is a volcanic island made of a'a lava in the Sunda Strait between the islands of Java and Sumatra in Indonesia. The name is used for the island group, the main island (also called Rakata), and the volcano as a whole. The island exploded in 1883, killing approximately 40,000 people, although some estimates put the death toll much higher. The explosion is considered to be the loudest sound ever heard in modern history, with reports of it being heard nearly 3,000 miles (4,800 km) from its point of origin. The shock wave from the explosion was recorded on barographs around the globe.