what is the opposing plate involved in the formation of the volcanoes of the islands sumatra and java?

Philippine plate

Explanation:

Eurasian plate from the northern and Australian plate from the southern sides and its eastwards movement is obstructed by the Philippine plate. This plate is moving at the speed of 3.2m/yr. The Eurasian plate is also being subducted beneath the Philippine plate. And java and Sumatra are a part of the Eurasian plate. This leads to the formation of volcanic arcs and festoons around this region, also this area is bombarded by most of the tectonic processes.