Raoul Island is the northernmost Kermadec island, and one of its most explosive and potentially destructive volcanoes. It is the largest of the Kermadec islands and has two active calderas about 3 km and 6 km across. Sometimes they have erupted simultaneously in historic times.
Intermittent eruptions over the last few thousand years have been explosive, with dacite magma (which is more silica rich and viscous than andesite).
Underwater on the flanks of Raoul Island there is an active volcanic cone about 240 metres high.
On 17th March 2006 a sudden and unpredictable eruption at Raoul destroyed a large area of bush and scatted rocks and ash over half the island. A Department of Conservation worker taking measurements at the crater lake at the time was tragically killed.