Sunda Trench in the context of "Indo-Australian plate"

The Lesser Sunda Islands (Indonesian: Kepulauan Sunda Kecil, Tetum: Illá Sunda ki'ik sirá, Balinese: ᬓᬧᬸᬮᭀᬯᬦ᭄ᬲᬸᬦ᭄ᬤᬘᬾᬦᬶᬓ᭄, romanized: Kapuloan Sunda cénik), now known as Nusa Tenggara Islands (Indonesian: Kepulauan Nusa Tenggara, or "Southeast Islands"), are an archipelago in the Indonesian archipelago. Most of the Lesser Sunda Islands are located within the Wallacea region, except for the Bali province which is west of the Wallace Line and is within the Sunda Shelf. Together with the Greater Sunda Islands to the west, they make up the Sunda Islands. The islands are part of a volcanic arc, the Sunda Arc, formed by subduction along the Sunda Trench in the Java Sea. In 1930 the population was 3,460,059; today over 17 million people live on the islands. Etymologically, Nusa Tenggara means "Southeast Islands" from the words of nusa which means 'island' from Old Javanese language and tenggara means 'southeast'.

The main Lesser Sunda Islands are, from west to east: Bali, Lombok, Sumbawa, Flores, Sumba, Savu, Rote, Timor, Atauro, Alor archipelago, Barat Daya Islands, and Tanimbar Islands. Apart from the eastern half of Timor island and Atauro island which constitute the nation of Timor Leste, all the other islands are part of Indonesia.

The Timor Sea (Indonesian: Laut Timor, Portuguese: Mar de Timor, Tetum: Tasi Mane or Tasi Timór) is a relatively shallow sea in the Indian Ocean bounded to the north by the island of Timor with Timor-Leste to the north, Indonesia to the northwest, Arafura Sea to the east, and to the south by Australia. The Sunda Trench marks the deepest point of the Timor Sea with a depth of more than 3300 metres, separating the continents of Oceania in the southeast and Asia to the northwest and north. The Timor sea is prone to earthquakes and tsunamis north of the Sunda Trench, due to its location on the Ring of Fire as well as volcanic activity and can experience major cyclones, due to the proximity from the Equator.

The sea contains a number of reefs, uninhabited islands and significant hydrocarbon reserves. International disputes emerged after the reserves were discovered resulting in the signing of the Timor Sea Treaty.

Oblique subduction is a form of subduction (i.e. a tectonic process involving the convergence of two plates where the denser plate descends into Earth's interior) for which the convergence direction differs from 90° to the plate boundary. Most convergent boundaries involve oblique subduction, particularly in the Ring of Fire including the Ryukyu, Aleutian, Central America and Chile subduction zones. In general, the obliquity angle is between 15° and 30°. Subduction zones with high obliquity angles include Sunda trench (ca. 60°) and Ryukyu arc (ca. 50°).

Obliquity in plate convergence causes differences in dipping angle and subduction velocity along the plate boundary. Tectonic processes including slab roll-back, trench retreat (i.e. a tectonic response to the process of slab roll-back that moves the trench seaward) and slab fold (i.e. buckling of subducting slab due to phase transition) may also occur.