In short, Merapi lies along a volcanic arc that formed by the subduction of the Indian Ocean plate beneath the Austro-Indian plate.
(Merapi; lies; along a volcanic arc) (a volcanic arc; formed; by the subduction of the Indian Ocean plate beneath the Austro-Indian plate)
Merapi a volcanic arc
lies formed
along a volcanic arc
by the subduction of the Indian Ocean plate beneath the Austro-Indian plate