map of south sandwich plate (san) shows its position between the scotia plate (sco), south american plate (sam) and the antarctic plate (ant). there are also visible the east scotia ridge (esr), south sandwich islands (ssi) and the south sandwich trench (sst).
the south sandwich trench is a deep arcuatetrench in the south atlantic ocean lying 100 kilometres (62 mi) to the east of the south sandwich islands. it is the deepest trench of the southern atlantic ocean, and the second deepest of the atlantic ocean after the puerto rico trench. since the trench extends south of the 60th parallel south, it also contains the deepest point in the southern ocean.
the deepest point in the entire trench is the meteor deep, whose location prior to february 2019 was identified as 55°25.12′s026°24.28′w / 55°25.12′s026°24.28′w / meteor deep) at a depth of 8,202 metres (26,909 ft). this sounding was made during the german meteor expedition. the depth is named after the german survey ship meteor, which first surveyed the area as part of its namesake expedition in 1926. the deepest point below the 60th parallel south, the deepest point in the southern ocean, is dubbed by victor vescovo as the factorian deep, a name that he hopes will become official. this point lies at a depth of 7,433.6 metres (24,388 ft), and is the only subzero hadal zone in the world.
the trench is 965 kilometres (600 mi) long and has a maximum depth of 8,266 metres (27,119 ft) below sea level at 55°13.47′s26°10.23′w / 55°13.47′s26°10.23′w / -55.22450; -26.17050, as measured by a kongsberg em124 multibeam sonar from february 2–7, 2019 during the five deeps expedition. this measurement was made during the first complete sonar mapping of the trench which covered its entire length, with a measurement error of +/- 11 metres (36 ft). the deepest point of the south sandwich trench is only 110 metres (361 ft) shallower than the deepest point in the puerto rico trench, sometimes known as the milwaukee or brownson deep.
the trench is produced by the subduction of the southernmost portion of the south american plate beneath the small south sandwich plate. the south sandwich islands constitute a volcanicisland arc which results from this active subduction. mount belinda on montagu island is an active volcano.