What is ocean continental subduction?

if lava appered as a dome on an island, and eruptions followed for a few years, that covered much of the island in ash. I need to know what is occuring to cause this volcanism, what features are found there, the plates that are causing this, what type of plates are they, what type of rock in on both plates, what is the process causing this plate movement and the reason for one plate to subduct. this is for an essay question for a test i am going to take in sience tomarow if you have any ideas or places i can look tell me. i have an idea it is ocean continental subduction.