The Ryukyu arc (琉球弧, Ryūkyū-ko) is a volcanic
island arc system of Japan's triple junction formed by the
subduction of the
Philippine Sea Plate beneath the
Eurasian Plate between
Ryukyu Trench to the south-east and the
Okinawa Trough to north-west.
 It comprises the entirety of the
Ryukyu Islands chain. The Ryukyu and
Southwest Honshu arcs together form the southwest trending arm of the
Boso Triple Junction.