Where it is
The Banda Sea Plate is a microplate of about 696,000 square kilometers, or 0.14% of Earth’s surface. It lies beneath the Banda Sea and the Flores Sea in eastern Indonesia. In PB2002 it also takes in about 6.5% of Indonesia’s land, including parts of Sulawesi and small islands such as the Banda Islands. The crust is mixed: mostly ocean floor, with fragments of continental and volcanic arc crust.
The plate sits inside the Banda Arc, a horseshoe of islands that curves from Timor through Tanimbar and Seram to Buru. This bend formed as the northern edge of the Australian continent entered the old Banda subduction zone, often cited as a modern example of a continent arriving at a trench.
What happens at its edges
All but one of the plate’s boundaries are convergent. The longest, 1,462 km, is with the Molucca Sea Plate to the north, moving at about 0.9-5.5 cm/yr. To the south, a 1,383 km boundary with the Timor Plate moves at about 2.3-3.5 cm/yr, mostly as oceanic convergence behind the arc.
To the west, a 977 km boundary with the Sunda Plate combines subduction, transform and collision at about 0.9-3.4 cm/yr. The fastest boundary is with the Bird’s Head Plate in the east, 800 km long and moving at about 6.5-7.7 cm/yr, mostly as subduction. Only a short 347 km stretch with the Australian Plate is divergent, opening at about 0.9-1.5 cm/yr.
Earthquakes and volcanoes
The dataset lists 61 earthquakes of magnitude 6.5 or larger on the plate since 1900. The largest is the 1938 Banda Sea earthquake (M8.5). Many others are deep, inside the slab beneath the sea: the 1996 earthquake north of Flores (M7.9) struck about 587 km down, the 2006 earthquake south of Ambon (M7.6) about 397 km down and a 1969 earthquake (M7.2) about 431 km down. A shallow strike-slip earthquake in the Flores Sea in 2021 (M7.3) caused a small tsunami.
The plate holds three volcanoes in the dataset. The best known is Banda Api, an island volcano in the Banda Islands that last erupted strongly in 1988. Serua is another remote island volcano in the inner Banda Arc.