Biogeochemical Responses to Mixing of Glacial Meltwater and Hot Spring Discharge in the Mount St. Helens Crater

Abstract

The mixing of geothermal waters and glacier meltwater is a widespread phenomenon but its chemical and microbiological effects on water quality are not fully understood. Approximately one fifth of the 1,443 known subaerial Holocene volcanic centers are glaciated or have permanent snowfields (Curtis & Kyle, 2017). These glaciated volcanoes occur on every continent and are particularly prominent in plate boundary and hotspot volcanic regions including, for example, the Cascades of the American northwest, Alaska, the Andes, Iceland, and the Kamchatka peninsula of Russia (Curtis & Kyle, 2017). Furthermore, subglacial volcanoes and geothermal heat are renowned for producing large quantities of meltwater that can result in glacial outburst floods, as is commonly observed in Iceland (Björnsson, 2002;Tomasson, 1996) and other regions around the world (Major & Newhall, 1989;Pierson et al., 1990). Volcanoes and geothermal sites are widespread in the heavily glaciated region of Antarctica, including at high elevations and along the margins of the continent in ice-free terrain (Fraser et al., 2014), as well as beneath the West Antarctic Ice Sheet, where 138 volcanoes have been identified (De Vries et al., 2018). Similar systems may also exist on other planetary bodies. For example, volcanism and glaciation have been dominant