"It stretches from northern Queensland to western Victoria"
from memory the "hotspot" volcanoes started around Bowen in Queensland and worked their way down and now are below the Great Australian Bight . The last land volcano was Mt Gambier .
I think the Tonga volcano has different origins and is in proximity of the Rim of Fire . I know there are some very deep trenches in this area .
I look forward to Volcanologist dissecting yesterdays eruption .
