Burrell Lapilli eruptives, Mount Egmont, New Zealand

Abstract

The Burrell Lapilli was erupted in 1655 A.D. over the ESE sector of Mount Egmont. Contour maps of Mø values, and the percentages of lapilli grade sizes > 16 mm and 16–8 mm, show lobes to the NE, SE, and ESE. The SE and ESE lobes coincide with lapilli positions on the isopach map but the NE lobe is not reflected in the thickness contours. The lower part of the lapilli deposit was distributed by winds blowing SE, the middle part by stronger winds blowing ESE, and the upper part by winds blowing NE. With increasing distance elongation axes of lobes for the isornedian and isopach maps rotate northwards indicating that during the main phases of eruption low level winds were WNW, while higher level winds were S or SW.