Anvil-shaped Raoul Island (Sunday Island), the largest and northernmost of the main Kermadec Islands, (located at (29°15′S177°55′W), 900 km (560 mi) SSW of 'Ata Island of Tonga and 1,100 km (680 mi) NNE of New Zealand's North Island), has been the source of vigorous volcanic activity during the past several thousand years that was dominated by dacitic explosive eruptions.