Sunda Trench

The Sunda Trench, also known as the Java Trench, is a very deep part of the ocean in the Indian Ocean near Sumatra. It was formed where the Australian-Capricorn plates move under a part of the Eurasian plate. This trench is very long, about 3,200 kilometres (2,000 miles), and its deepest point reaches 7,290 metres (23,920 feet) below sea level, making it the deepest spot in the entire Indian Ocean.

The trench runs from the Lesser Sunda Islands past Java, along the southern coast of Sumatra, and all the way to the Andaman Islands. It marks the boundary between the Indo-Australian plate and the Eurasian plate, specifically the Sunda plate. Because of its location, the Sunda Trench is part of the Alpide belt and one of many deep ocean trenches around the northern edges of the Australian plate.

In 2005, scientists found evidence that activity from a big earthquake in 2004 near the Java Trench could cause more dangerous shifts in the Earth’s surface in the future, possibly within just a few years. Because of this risk, countries agreed to set up a tsunami warning system along the Indian Ocean coast to help keep people safe.

Characteristics

Main article: Geology of the Sumatra Trench

The Sunda Trench has a special shape for about half its length near Sumatra. An underwater ridge splits it into two parallel troughs, and much of the trench is filled with sediments. After the 2004 Indian Ocean earthquake, maps of the area showed the trench looked like suspension bridge cables, with peaks and sags. This suggests there are locked faults, unlike the usual wedge shape expected for such trenches.

Exploration

Scientists first studied the Sunda Trench in the late 1950s. They used special tools to measure how deep it was and learned more about how the Earth’s layers move under the ocean.

In 2019, a person went down in a special submarine to the deepest part of the trench. They found it to be very deep and shared their information to help others learn more about the ocean. This was part of a big project to explore the deepest points in all the world’s oceans.

Associated seismicity

Main article: Sunda megathrust

The movement of the Indo-Australian plate moving under part of the Eurasian plate causes many earthquakes. Some of these earthquakes were very powerful and caused big waves in the ocean, affecting many people.

Sumatra segment

• 1797 Sumatra earthquake: magnitude 8.6–8.8
• 1833 Sumatra earthquake: magnitude 8.8–9.2
• 1861 Sumatra earthquake: magnitude ~8.5
• 1935 Sumatra earthquake: magnitude 7.7
• 2000 Enggano earthquake: magnitude 7.9
• 2002 Sumatra earthquake: A magnitude 7.3 earthquake.
• 2004 Indian Ocean earthquake and tsunami: Mw 9.2–9.3
• 2005 Nias–Simeulue earthquake: magnitude 8.6
• 2007 Bengkulu earthquakes: Series of earthquakes.
• 2008 Simeulue earthquake: magnitude 7.4
• 2009 Sumatra earthquakes: magnitude 7.6
• 2010 Mentawai earthquake and tsunami: magnitude 7.8

Java segment

• 1917 Bali earthquake: magnitude 6.6
• 1994 Java earthquake: magnitude 7.8
• 2006 Pangandaran earthquake and tsunami: magnitude 7.7
• 2009 West Java earthquake: magnitude 7.0
• 2019 Sunda Strait earthquake: magnitude 6.9