2016-2017 USAP Field Season
Erebus volcano: Characterizing a subglacial hydrothermal system and potential effects on CO2 degassing
Dr. Tobias P Fischer
University of New Mexico
Supporting Stations: McMurdo Station
Erebus Volcano is a natural laboratory of magmatic processes and the ideal place to investigate magma degassing. Although the degassing processes from the active lava lake have been studied in detail over the past decades, comparatively little work has been done on the processes that affect flank degassing. Erebus is glaciated and is the site of ice towers and caves that are the surface expression of heat and volatiles escaping from the edifice into the atmosphere. Contrary to non-glaciated volcanoes where flank degassing is often diffuse and challenging to identify, the ice caves provide visible clues to the escape of gases and heat. Preliminary gas sampling from five of the estimated 100 ice caves shows that gas compositions are dominated by a fractionated air component, with minor amounts of carbon dioxide, methane, and dihydrogen. Significantly, the relative abundance of air-derived gases strongly suggests the presence of an aqueous phase below the surface. Into this liquid, magmatic- and air-derived gases dissolve. As the liquid moves away from the crater area, it cools, eventually freezes, and, during this process, releases the gases through the ice caves. The goal of this project is to better characterize the liquid phase in terms of temperatures, gas contents, and its effect on carbon dioxide dissolution and degassing.
Field Season Overview
Team members will deploy by helicopter to the Lower Erebus Hut (LEH) for three weeks to collect gas samples. With the assistance of an ASC mountaineer, they will collect samples from approximately 20 to 25 previously-visited caves along ice-tower ridge, in the Sauna cave region, and close to the main crater rim. They will also deploy a small portable gas sensor at the crater rim to measure the CO2 and SO2 concentration in the plume. This data, combined with SO2 flux measurements, will enable the researchers to calculate crater CO2 flux and compare it to the data they obtain from the ice caves. In the caves, they will leave each vent sampling device in situ for 24 hours, with four vent sampling instruments deployed concurrently. In the caves and in warm ground areas, they will take CO2 flux samples along a grid area. Some gas samples will be analyzed on site at LEH with a laser spectrometer; others will be transported back to the home institution for analyses.
Deploying Team Members