Pu'u Wa'awa'a Pumice and Obsidian (Hawai'i)

Guest Post by Anne Fulton


19° 48' 21.08" N 155° 50' 34.26" W (WGS84) (Google Maps)

Land Status:

Hawai'i State Forest Reserve


Pu'u Wa'awa'a is a trachyte pumice cone on the north rift zone of Hualalai, standing at 372m (1,220 ft) tall and over 1.6 km (1 mi) in diameter. It represents the oldest exposed rocks on Hualalai at ~114 ka. The cone is composed of bedded pumice and obsidian blocks, which are likely the products of volatile-rich evolved liquid at the top of the magma reservoir. The obsidian blocks are concentrated toward the bottom of the exposed unit. This is likely due to the "throat clearing" of a glassy plug at the start of the eruption. Intermittent column collapse produced repeated units with graded bedding. Some pumice lenses do not contain much or any obsidian.

Pu'u Wa'awa'a is found off of Highway 190 (turnoff at coordinates above) behind a hunting gate that is open during daylight hours. Drive past the first parking area and continue to the left to the upper parking area where there is a small structure and outhouse. From the trailhead just beyond the gate, the base of the cone is about a mile hike up a paved road. The road ends at an old quarry where the pumice layering is beautifully exposed. The largest blocks of obsidian are exposed on the left-most side (SE) of the quarry. They range from 1-30 cm. A paleosol (ancient preserved soil) and Mauna Loa lava flow cap the deposits at the base of the cone.


An Occurence of Trachyte on the Island of Hawaii, W. Cross, The Journal of Geology, 1904.

Chronology, chemistry, and origin of trachytes from Hualalai Volcano, Hawaii, B.L. Cousens et al., Geochem. Geophys. Geosys., 2003.

Hawai'i Volcano Observatory - Obsidian

Hawai'i Volcano Observatory - When Hualalai Turned Viscous

Pu'u Wa'awa'a Ahupua'a Visitor Guide

Road leading to quarry

Pumice layering with paleosol and basalt cap

Chunks of obsidian exposed in the pumice

Site visited on 7/17/2016Page created on 10/22/2017