CONTINUOUS MONITORING OF THE HYDROTHERMAL SYSTEM AT LASSEN VOLCANIC NATIONAL PARK, CALIFORNIA

This work reports on a new protocol to monitor short term changes within the geothermal system of Lassen Volcanic National Park (LVNP). Newly implemented techniques are founded on the idea that as magmatic activity of the system changes, the temperature of the lake will also vary. Two sites have been targeted at LVNP, Sulfur Works and Boiling Springs Lake. By monitoring temperature variations of the lake and fumaroles, we will accumulate background data for the hydrothermal system at LVNP to better characterize the magmatic system. Temperature data have been collected continuously since June 2007, as well as surface water pH and CO2 at both sites. Each system has high acidity (average pH less than 2.2), requiring careful consideration in the installation of data collection probes. Water temperature data are collected by a stainless steel Hobo data logger housed in PVC tubing, submerged in the water bodies. In one day, data can be downloaded and collection restarted for nearly uninterrupted measurements. Sulfur Works fumaroles range in temperature from 68-78 C and temperatures at Boiling Springs Lake range from 44-57 C. Temperature variations are not on diurnal cycles, and do not correlate consistently between sites, nor with air temperatures. Data are recorded at 15-30 minute intervals over the course of 1-3 month installation periods. CO2 measurements are also completed during site visits, but are not yet continuously recorded. GPS mapping (sub-meter accuracy) of hydrothermal areas provides graphic detail and visual descriptions of monitoring sites, such as locations and data collected for various fumaroles and mud pots. Results of this work will provide continuous monitoring at LVNP, but are also part of an effort to develop potentially long term monitoring programs for volcanoes with crater lakes that are less accessible such as those in Costa Rica.