UH Hilo Center for Maunakea Stewardship - Research Library

Pleistocene subglacial eruptions on Mauna Kea

Author:
Porter, Stephen C.
Title:
Pleistocene subglacial eruptions on Mauna Kea
Periodical:
Volcanism in Hawaii, U.S. Geological Survey Professional Paper 1350
Year:
1987
Pages:
p.587-598
Subject:
Glaciation Mauna Kea volcano
Summary:
A distinctive assemblage of pyroclastic cones and lava flows inside the limit of Pleistocene glaciation on the upper slopes of Mauna Kea Volcano is attributed to subglacial eruptions during two intervals when an ice cap mantled the summit of the mountain. During the Waihu glaciation, when an ice cap of about 140 km (super 2) formed, eruptions built two pyroclastic cones composed of hyaloclastite tuff capped by subaerially erupted bomb-bearing cinder deposits. Associated lava flows have steep embayed margins and glassy surfaces, and are locally palagonitized. A bouldery conglomerate on the southwestern flank of the volcano is inferred to have resulted from floods caused by failure of glacier-impounded lakes that formed over the erupting vents. A younger group of cones and lava flows was erupted during the Makanaka glaciation, when a smaller ice cap (70 km (super 2) ) mantled the summit. A seismic discontinuity in one of these cones may mark a boundary between a hyaloclastite core and overlying hydrothermally altered cinders that are exposed locally. Associated lavas are characterized by steep margins, pillows, glassy surfaces, spiracles, and palagonitized zones. The morphology of flow margins suggests that ice was thin along rift zones but thickened away from them. Stratigraphic relations and radiometric ages show that the Waihu-age eruptions occurred during marine isotope stage 6, and the Makanaka-age eruptions took place either during stage 3 or near the end of stage 4. Although firm evidence of subglacial eruptions earlier than the Waihu glaciation is lacking, such events are likely to have occurred during the Pohakuloa glaciation (isotope stage 8) at the close of the tholeiitic shield-building phase of Mauna Kea's growth.
URL:
http://pubs.usgs.gov/pp/1987/1350/
Collection:
Monographs