Which ocean contains the Sunda Trench?

The Sunda Trench lies in the Indian Ocean.

Also called the Java Trench in some contexts, it follows the southern margins of Sumatra and Java and extends toward the Lesser Sunda Islands. It formed where the Indo-Australian Plate is subducting beneath the Sunda portion of the Eurasian Plate, making it part of a major earthquake and tsunami-producing boundary.

The trench is about 3,200 kilometres long, and its deepest point is roughly 7,290 metres below sea level. During the Five Deeps Expedition, DSV Limiting Factor made the first crewed descent to its deepest area on 16 April 2019. Later surveying confirmed that the Sunda Trench is deeper than the Diamantina Fracture Zone, settling a debate about the Indian Ocean’s deepest point.

The main mix-up is geographical: the trench is near Indonesia, but it is not in the Pacific Ocean. The Pacific’s deepest feature is the Mariana Trench, while the Atlantic’s deepest point is in the Puerto Rico Trench. The Sunda Trench marks a boundary between tectonic plates and is closely associated with the devastating 2004 Indian Ocean earthquake and tsunami.