Lava and ice interaction at stratovolcanoes: Use of characteristic features to determine past glacial extents and future volcanic hazards

Abstract

Abstract. Structures resulting from lava and ice interaction are common at glaciated stratovolcanoes. During summit eruptions at stratovolcanoes, meltwater is produced and travels freely down steep slopes and thin permeable valley glaciers, eroding the ice and enlarging preexisting glacial drainages. As a result, eruptions in this environment have produced few catastrophic floods. Lava flowing into the open channels and voids in the glaciers becomes confined and grows thicker, filling the available space and producing steepsided bodies with smooth, bulbous contact surfaces. Quenching of lava against ice or by water forms small-scale features such as tensional fractures and glass. As the amount of meltwater in contact with the lava increases, the type and abundance of smaller-scale features become similar to those produced during subglacial eruptions into meltwater lakes. Identification of large-and small-scale lava-ice contact features in the field can be used to reconstruct paleoglacial extent and, combined with geochronology of lavas, to determine past paleoclimate. An understanding of lava-ice interaction allows us to better assess the hazards posed by future eruptions at glaciated volcanoes.

Field-trip guide to mafic volcanism of the Cascade Range in Central Oregon—A volcanic, tectonic, hydrologic, and geomorphic journey

“…Hogg Rock has an age of 0.08 Ma (Hill and Priest, 1992), which is correlative with the onset of Wisconsin-age glaciation. The spectacular exposure of glassy, fine-scale columnar jointing in the Hogg Rock roadcut provides an example of ice-contact morphology, in which the columnar jointing formed by rapid cooling of the lava at the ice (water) interface (see, for example, Lescinsky and Fink, 2000).…”

Geologic field trip guide to Mount Mazama and Crater Lake Caldera, Oregon

“…Similarly, ice contact features (Lescinsky and Fink, 2000) are common in some units (for example, unit aa). The table mountain or tuya morphology and structure (Mathews, 1947) of some monogenetic volcanoes near Mount Mazama also indicate presence of ice of a specific minimum thickness at the time of eruption (units at and ab).…”

“…Platy joints may wrap onion-like around the interior of a flow so that plates are steep at flow margins. Lava erupted when ice was present displays ice-contact and water-chilling features, such as closely spaced vitric columns that are 10-20 cm in cross section (polygonal joints; Lescinsky and Fink, 2000), often in unusually great thicknesses, and that may grade up into vitric breccia (for example, unit aa on Dutton and Grayback Ridges and at Wineglass; andesite of Llao Bay, upper unit alu, near Pumice Point).…”

How will melting of ice affect volcanic hazards in the twenty-first century?

“…Historical eruptions at more than 40 volcanoes worldwide have involved disruption of ice and snow (Major & Newhall 1989), whereas numerous geological studies have enabled the recognition of interactions between volcanoes and ice or snow in ancient eruptions (e.g. Noe-Nygaard 1940;Mathews 1951;Gilbert et al 1996;Smellie 1999;Lescinsky & Fink 2000;Mee et al 2006). Volcanic deposits provide an invaluable record of palaeo-environmental change, such as fluctuations in ice thickness and extent (Smellie 2008;Smellie et al 2008;Tuffen et al in press), as well as the processes and hazards associated with various types of volcano-ice interaction (e.g.…”

“…Volcanic deposits provide an invaluable record of palaeo-environmental change, such as fluctuations in ice thickness and extent (Smellie 2008;Smellie et al 2008;Tuffen et al in press), as well as the processes and hazards associated with various types of volcano-ice interaction (e.g. Smellie & Skilling 1994;Smellie 1999;Lescinsky & Fink 2000;Carrivick 2007;Tuffen & Castro 2009). …”