Curtis and nearby Cheeseman Islands are the emergent portions of a submarine volcano along the Kermadec Ridge. The age of the small islands are considered to be Pleistocene, and rocks consist dominantly, if not entirely, of andesitic pyroclastic-flow deposits (Lloyd, 1992). Curtis Island, 500 x 800 m, contains a large fumarolically active crater whose floor is only 10 m above sea level. Reports of possible eruptions probably represent increased thermal activity. Geologic studies have documented 18 m of uplift during the past 200 years, with 7 m occurred between 1929 and 1964 (Doyle et al., 1979). An active submarine magmatic or solfataric vent is believed to exist nearby, but its activity cannot unequivocally be associated with the volcano (Lloyd, 1992).