Island. Geography Two Holocene calderas are found at Raoul. The older caldera, which cuts the center of Raoul Island, is about long and wide respectively. Denham caldera, formed during a major dacitic explosive eruption about 2200 years ago, truncated the western side of the island and is long and wide respectively. 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 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 by Royal Navy Captain Henry Mangles Denham in HMS Herald, who came to complete a (chart) survey of the island on 2 July 1854. His son Fleetwood James Denham (16yrs) died from a tropical fever, and was buried near the beach at the head of Denham Bay, where a number of the grass-grown graves of former settlers were. The brass plaque heading this grave has been preserved. Three small lakes, Blue Lake (, about 40% overgrown), Green Lake () and Tui Lake (, drinking water quality) are located in the northern caldera of Raoul Island. The plains surrounding the lakes are called Pumice Flats. Climate Raoul Island has a humid subtropical climate close to the border of tropical climate (Cfa). On February 12, 2022, the minimum temperature in the Raoul Island was 25.6 °C, this is the highest minimum temperature ever recorded in New Zealand. Flora and fauna The scientific categorisation of the flora and fauna of the island began in 1854 when , captained by Henry Mangles Denham, arrived to complete the charting of the island. He arrived on the 2nd and was occupied till 24 July, during which time he frequently had to move the ship on account of the rough weather experienced. William Grant Milne and John MacGillivray, naturalists on board the Herald, made a small collection of plants on Raoul. This was forwarded by Captain Denham to Sir W. Hooker, and was described by Sir Joseph Hooker in the Journal of the