Brief Overview of Lassen Volcanic National Park

      The Lassen volcanic center in north central California is the southernmost active volcanic system in the Cascade Range.  Lassen Peak, which formed 27,000 years ago in a large eruptive event, reawakened in May 1914 and continued erupting intermittently for a period of four years.  Silicic volcanism at Lassen over the past 300,000 years has greatly altered the surrounding landscape and created the thermal features that today are characteristic of LVNP.  Roaring fumaroles, mudpots, boiling pools, and steaming ground are present in various locations throughout the LVNP vicinity.  Within the park boundaries are several high-elevation, acid-sulfate, low chloride springs characteristic of vapor-dominated hydrothermal systems (12). These thermal acidic features represent some of the most extreme life-supporting environments on earth with temperatures ranging from 50 C-115 C, and pH from 0-3.  Only a small number of studies have examined biology in the acidic, thermal features at Lassen Volcanic National Park (9, 29), and these have focused on narrow taxonomic groups.

      Throughout the past several years, U.S. Geological Survey volcanologists have undertaken detailed investigations of geothermal features in LVNP(12, 16, 25, 26). Previous geochemical data from various sites within LVNP indicate that geochemical composition of springs varied widely even among features in similar regions of the park with similar temperatures and pH values (26). Previous gas analyses (mid 1990’s) of features in several locations within LVNP indicate the volcanic gases emitted from different thermal features vary significantly among different thermal regions within LVNP; however, most features analyzed within a given region have similar gas compositions (C. Janik, U. S. Geological Survey, unpublished results). The Upper Sulfur Works (USW) and Lower Sulfur Works (LSW) sites were the lowest in average mole percent H2S, CH4, and H2 (0.41, 0.0025, and 0.047, respectively) when compared to features in Bumpass Hell (BH) (6.31, 0.079, and 0.90, respectively), Devil’s Kitchen (DK) (3.56, 0.109, and 0.4, respectively), and the Boiling Springs Lake thermal area (BSLTA) (6.95, 0.072, and 0.275, respectively) (Table 2).  As is common for gases emitted from geothermal features, the mole percent dry weight CO2 was high in all sites [averages of 89.9 (BH), 98.7 (SW), 92.33 (DK), and 88.7 (BSLTA)]. We have recently extended these analyses to obtain geochemical composition of waters associated with several features that we are characterizing biologically