The motions between the Somalian, Antarctic, and Australian plates-the
three plates believed to meet at the Rodrigues triple junction in the
Indian Ocean-are inconsistent with the assumption that all three plat
es are rigid. The discrepancy is best explained if the Australian plat
e contains two component plates. Thus, the traditionally defined Indo-
Australian plate consists of three component plates and multiple diffu
se plate boundaries. The pattern of present deformation indicates that
the boundaries between the th ree component plates are two unconnecte
d zones accommodating divergence and a larger zone, which we interpret
as three diffuse convergent plate boundaries and a diffuse triple jun
ction.