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Title: Puu Mahana Near South Point in Hawaii Is a Primary Surtseyan Ash Ring, Not a Sandhills-type Littoral Cone 
Author: Walker, George PL
Date: 1992-01
Publisher: University of Hawai'i Press
Citation: Walker GPL. 1992. Puu Mahana near South Point in Hawaii is a primary Surtseyan ash ring, not a sandhills-type littoral cone. Pac Sci 46(1): 1-10.
Abstract: Puu Mahana has previously been interpreted to be a littoral cone,
formed at a secondary rootless vent where lava flowed from land into the ocean,
but a number of lines of evidence point to it being a remnant of a Surtseyan tuff
ring built on a primary vent. The differences between it and littoral cones are
highlighted by a comparison of Puu Mahana with the undoubted littoral cone
of the Sandhills that was observed to form in the 1840 flank eruption of Kilauea
Volcano. Puu Mahana contains abundant lithic debris and accretionary lapilli,
absent in the Sandhills deposit. Compared with the Sandhills, the Puu Mahana
pyroclastic deposit is finer grained and more poorly sorted, and its juvenile
component is less dense and more highly vesiculated. Puu Mahana lies 3 to 4 km
offMauna Loa's southwest rift zone. Identification of it as a primary vent implies
that the lower rift zones of Hawaiian volcanoes can be much wider and more
diffuse or more mobile than is currently acknowledged. The olivine grains that
compose the well-known green-sand beach at Puu Mahana are likely derived
from the ash, strongly concentrated and somewhat abraded by wave action.
ISSN: 0030-8870
URI: http://hdl.handle.net/10125/1669

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