Shore based observations had characterised the islands of the volcanic arc as having typical lavas and being of early
Miocene or younger in age. More recently marine surveys have supplemented this limited sampling. Reef terraces mantle on Espiritu Santo and
Malekula show rapid late
Quaternary terrace uplift of between . This material is lighter than the other subducted zone material except for West Torres Plateau material and this property is believed to be a factor in distortions of the island arc chain at these subduction points. The rest of the oceanic basalt crust of the Australian plate that is being subducted otherwise is
Eocene in age.
Tectonics The zone defines the
plate boundary between the
New Hebrides microplate, which is related to the
Pacific plate, and the
Australian plate. Ten million years ago the Vanuatu island chain had an almost east west orientation with Fiji and the spreading centers of the
North Fiji Basin have created both the current separation and quite different orientation. The convergence rate in the subduction zone has a high rate of /year in the north at about latitude 11°S in the
Solomon Island region, north of the
Torres. The ridge may have been subducting for up to the last two million years. To the south subduction ceases at the triple junction with the
Conway Reef microplate under the North Fiji Basin with the rest of the convergence being accommodated by less tectonically active
rifting in the western stretch of the New Hebrides Trench, the Hunter Ridge to its north and the
Hunter fracture zone which is a transform faulting
fracture zone continuation of the trench towards
Fiji. This triple junction is where from 3 million years ago the southernmost Central Spreading Ridge of the North Fiji Basin propagated southward and has now intersected with the New Hebrides Trench and the Hunter fracture zone. The epicenter was close to
Matthew Island, to the north of the trench and was both preceded and followed by a seismic crisis of multiple events with greater than Other significant earthquakes may be found in the
list of earthquakes in Vanuatu,
list of earthquakes in the Solomon Islands archipelago and
New Hebrides Trench articles.
Tsunami hazard The tsunami resulting from the
2013 Solomon Islands earthquake was high at the town of
Lata on
Nendö in the
Santa Cruz Islands and resulted in ten deaths. So did
Epi and
Ambae, which is Vanuatu's most voluminous active volcano. In 2022
Ambrym and the
Gaua volcanoes erupted. ==References==