How long is the Sunda Trench?

The Sunda Trench is approximately 3,200 kilometres long. It follows the curved boundary where the Australian–Capricorn plate system descends beneath the Eurasian Plate, specifically the Sunda Plate, in the eastern Indian Ocean.

Its route begins near the Lesser Sunda Islands, continues past Java, and curves around the southern coast of Sumatra toward the Andaman Islands. Because it spans several island regions, older references may call portions of it the Java Trench, but the 3,200-kilometre figure applies to the broader feature now generally called the Sunda Trench.

The trench is not a simple, uniformly shaped groove. Off Sumatra, an underwater ridge divides roughly half of it into two parallel troughs, and sediment partly fills much of the structure. Its deepest point is about 7,290 metres, making it the deepest location in the Indian Ocean. The trench’s length and active plate boundary also help explain the region’s powerful earthquakes and tsunami risk.