Pleistocene snowlines and glaciation of the Hawaiian Islands

High volcanoes on two of the southeastern Hawaiian Islands experienced Pleistocene ice-cap glaciations. Drifts of three glaciations on the upper slopes of Mauna Kea (4206 m) are interstratified with lavas. During marine isotope stage (MIS) 2, an ice cap (70.5 km2) formed when the snowline fell ca. 930 m to an altitude of ca. 3785 m. Drifts of MIS 4 and 6 age, largely buried by hawaiite lavas, record a snowline about 100 m lower. Holocene lavas bury the upper slopes of Mauna Loa (4169 m), the summit of which likely intersected the snowline during the last glaciation. The reconstructed history of snowline variations and glaciation on Maui's Haleakala (3055 m) relies on evidence of the island's growth, isostatic subsidence, and tilting. The snowline may first have intersected Haleakala about 800,000 years ago; ice caps waxed and waned during the next ca. 400,000 years (MIS 22-12) until subsidence and diminishing eruptive activity brought the summit below the snowline. Erosional morphology and thick diamictons indicative of subglacial eruptions are consistent with repeated summit glaciations. Whereas Haleakala's glacial history has ended, ice caps likely will regenerate on Mauna Kea ca. 60,000 and 100,000 years in the future, after which the summit will subside below the glacial-age snowline.