how are island arcs created

hot spots in the earths core cause intense heating of the crust. This heating causes magma to rise and break the sea floor. a volcano is formed. Over time, due to tectonic plate movement (wegener) the crust moves over the hot spot and consequently heats and forms a new volcano. The old volcano is now dormant and disused. E.G island arc in hawaiii... bikini is nearly under water +diagram... (four volcanoes, each of diminishing size)