Raoul Island - Definition and Overview

Anvil-shaped Raoul Island, the largest and northernmost of the Kermadec Islands, (New Zealand), has been the source of vigorous eruptive activity during the past several thousand years that was dominated by dacitic explosive eruptions.

Two Holocene calderas are found at Raoul. The older caldera cuts the center of Raoul Island is about 2.5 x 3.5 km wide. Denham caldera, formed during a major dacitic explosive eruption about 2200 years ago, truncated the western side of the island and is 6.5 x 4 km wide. Its long axis is parallel to the tectonic fabric of the Havre Trough that lies west of the volcanic arc. Historical eruptions at Raoul during the 19th and 20th centuries have sometimes occurred simultaneously from both calderas, and have consisted of small-to-moderate phreatic eruptions, some of which formed ephemeral islands in Denham caldera. A 240-m-high unnamed submarine cone, one of several located along a fissure on the lower NNE flank of Raoul volcano, has also erupted during historical time, and satellitic vents at Raoul are concentrated along two parallel NNE-trending lineaments. The Denham caldera was named for the nearby Denham Bay, itself named for Captain Denham from the H.M.S. Herald, an early explorer of the island.

Two small lakes, Blue Lake and Green Lake are located on Raoul Island. Neither has a surface area of over 100 hectarees.

In 2004 rats, an introduced pest, were successfully eradicated from the island. The island is part of New Zealands largest marine reserve which was created in 1990.

External link

• Department of Conservation (http://www.doc.govt.nz/Conservation/Marine-and-Coastal/Marine-Reserves/040~Kermadec/index.asp) - government agency responsible for administering the island.