Three Compliance Instruments for Axial Volcano to Observe Long Term Evolution of the Magma Chamber and in Support of OOI Observations
Despite decades of observations, how magma migrates and is stored within volcanoes remains poorly understood because there are few means to continuously monitor changes within magma chambers beneath volcanoes. Such measurements are needed to understand when and how the gradual emplacement of magma finally triggers an eruption. The instrumentation developed will provide the potential to monitor changes in the magma content continuously beneath undersea volcanoes and thereby provide a better understanding of volcano processes that can also be applied to volcanos on land that pose a major hazard to millions of people.
Axial Volcano, a large, very active undersea volcano offshore the US West Coast is currently monitored using sensors that transmit data through the NSF supported Ocean Observatories Initiative cable to shore. Sensors on these cables measured changes in the compliance of seafloor preceding and following an eruption in 2015 associated with changes in the magma chamber, but the noise level of these sensors limited the sensitivity of the observations and the observation period to the winter months when the compliance signal was larger. New compliance sensors with better sensitivity and a lower noise level will be constructed using more optimal sensors and placed on the seafloor beneath large shields that protect the sensors from noise from ocean currents. Compliance, a measure the deformation of the seafloor under the loading of long period ocean waves, depends on the elastic properties of the underlying Earth and thereby to the fraction of magma within the magma chamber. The current shielding developed will also have applicability for reducing the noise levels for the horizontal components of broadband seismometers installed on the seafloor. Ocean bottom seismometers are critical to understanding many Earth processes, but the high noise levels due to ocean floor currents limits the types and quality of observations that can be made.