I am from Oklahoma and currently live in Norman, OK and we have had 65 "felt/registered" earthquakes in the past year; quite unusual.
Active volcanoes are rare in Australia because there are no plate boundaries on this continent.
However, there are two active volcanoes located 4,000 kilometres south-west of Perth on the Australian territories, Heard Island and the nearby Mc Donald Islands.
The denser plate, which invariably has oceanic crust on its top, does the sinking.
Second, only earthquakes occur when two plates collide (obduct), building a mountain range.