Geologic Background:
Anvil-shaped Raoul Island, the largest and
northernmost of the Kermadec Islands, has been the source
of vigorous eruptive activity during the past several
thousand years that was dominated by dacitic explosive
eruptions. Two small Holocene calderas are found on the
island, one at Denham Bay on its west side. The Denham
Bay caldera was created during the largest Holocene
eruption, a little more than 2100 years before present.
Historic Activity:
- Historical eruptions during the 19th and 20th
centuries have occurred simultaneously from both
calderas, and have consisted of small-to-moderate
phreatic eruptions, some of which formed ephemeral
islands in Denham Bay.
- Major hydrothermal eruption occurred on Nov. 20,
1964. The 1964 eruption was primarily phreatic and formed
12 small craters in Raoul Caldera. A submarine eruption
in Denham Bay is believed to have occurred at about the
same time.
Recent Activity:
- The srongest earthquake swarm since the 1964 eruption
occured on March 9, 1993.
Data Sources:
- Global Volcanism Network (V. 15, No. 3 and V. 18, No.
3).
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