ASSESSING THE GLOBAL POTENTIAL FOR VOLCANO-GLACIER INTERACTIONS

We have created a database documenting the global occurrence of potentially active volcanoes and nearby glaciers from existing sources (Global Volcanism Program and GLIMS). Our analysis shows that 267 terrestrial volcanoes presently have at least one glacier within 1 km, 290 have glaciers with 2.5 km, and 318 have glaciers within 5 km. South America has the largest number of glacierized volcanoes (>72), followed by Alaska, Antarctica and Kamchatka/Asia. Our analysis also shows that 951 glaciers are within 1 km of a volcano, 1892 are within 2.5 km, and 3485 are within 5 km. Ice at any of these distances could potentially be affected by eruptions from nearby volcanoes, with important implications for hazard assessments, freshwater resources, and assessing climate change. Volcanic eruptions affect nearby glaciers in several ways. Both explosive and effusive eruptions cause damage to surrounding ice. While explosive eruptions can produce near instantaneous melting of ice from pyroclastic density currents (e.g., Mount St. Helens, 1980; Nevado del Ruiz, 1985), lava eruptions can also significantly impact surrounding ice (Eyjafjallajokull, 2010). Interactions from explosive eruptions are complex in that, while thin ash cover may increase rates of ice melting in the short term, thicker ash deposits can shield ice from annual solar-driven melting.Glacier melting during eruptions can produce short-term and long-term impacts on humans. Melt-generated lahars travel 10’s of km from their source area and cause significant loss of life and property. Many global communities in arid climates also rely on glacier-held water to support agriculture (e.g., Nevado Coropuna, Peru); damage from eruptions can be so severe that ice volumes never recover (e.g., Gigjokull glacier, Iceland). Having a global database of volcanoes in close proximity to ice is the first step towards generating individual assessments for glaciers most likely to be impacted by future volcanic activity.