Gas chemical and isotopic compositions are reported for samples collected from 9 volcanic and geothermal areas in California: Medicine Lake Volcano, Mount Shasta, Lassen Volcanic Center, Clear Lake Volcanic Field, Mono Lake Volcanic Field, Long Valley Caldera, Mammoth Mountain, Coso Volcanic Field, and Salton Sea Geothermal Field. Beginning in 2014, gas samples were collected as part of the USGS California Volcano Observatory's newly established gas geochemical monitoring program for moderate to very-high-threat volcanoes. Data on gas samples collected prior to 2014 by this and previously published studies are also reported to provide longer-term records for some areas. Gas samples in this study were analyzed for chemical (CO2, H2S, He, H2, Ar, O2, N2, NH3, CH4, C2H6, CO, C3H8, and C4H10) and isotopic (R/RA, d13C-CO2, d13C-CH4, dD-steam, d18O-steam) compositions at USGS laboratories in Menlo Park, California, Denver, Colorado, and Reston, Virginia. The chemical and isotopic data are saved in three spreadsheets in the *.csv format.

Water and gas chemistry data from: Mariner, R.H., Presser, T.S. and Evans, W.C., 1977. Hot springs of the central Sierra Nevada, California: U.S. Geological Survey Open-File Report 77-559, 37 p., https://doi.org/10.3133/ofr77559. Water chemistry data was digitized for 21 samples. Reported attributes include: Sample name, Type, Reported location, Location description, State, County, Latitude, Longitude, Location resolution, Location error, Temperature, pH (field), Aluminum (Al), Boron (B), Calcium (Ca), Chloride (Cl), Cesium (Cs), Copper (Cu), Fluoride (F), Iron (Fe), Hydrogen sulfide (H2S), Bicarbonate (HCO3), Alkalinity as bicarbonate (HCO3), Mercury (Hg), Potassium (K), Lithium (Li), Magnesium (Mg), Manganese (Mn), Sodium (Na), Ammonium (NH4), Nickel (Ni), Rubidium (Rb), Silica (SiO2), Sulfate (SO4), Zinc (Zn), Cations, Anions, Reported total dissolved solids, Salinity, Charge balance, Isotopic composition of hydrogen (Delta 2H), Isotopic composition of oxygen in water (Delta 18O H2O), Oxygen shift, Digitizer comment. Gas chemistry data was digitized for 12 samples. Reported attributes include: Sample name, Type, State, County, Latitude, Longitude, Location resolution, Location error, Total gas, Oxygen and argon (O2 + Ar), Ethane (C2H6), Methane (CH4), Carbon dioxide (CO2), Nitrogen (N2), Author comment, Digitizer comment. Data was digitized from Tables 1, 3, 4, 5, 7, 9, and 10. The following tables were not digitized: Table 2: age and lithology of the bedrock at each thermal spring. Table 6: the mole ratios of major to minor constituents of thermal springs. Table 8: the equilibrium states of reactions in the thermal springs. Table 11: measured temperatures and estimated reservoir temperatures for the thermal springs.

Water and gas chemistry data from: Mariner, R.H., Presser, T.S. and Evans, W.C., 1977. Hot springs of the central Sierra Nevada, California: U.S. Geological Survey Open-File Report 77-559, 37 p., https://doi.org/10.3133/ofr77559. Water chemistry data was digitized for 21 samples. Reported attributes include: Sample name, Type, Reported location, Location description, State, County, Latitude, Longitude, Location resolution, Location error, Temperature, pH (field), Aluminum (Al), Boron (B), Calcium (Ca), Chloride (Cl), Cesium (Cs), Copper (Cu), Fluoride (F), Iron (Fe), Hydrogen sulfide (H2S), Bicarbonate (HCO3), Alkalinity as bicarbonate (HCO3), Mercury (Hg), Potassium (K), Lithium (Li), Magnesium (Mg), Manganese (Mn), Sodium (Na), Ammonium (NH4), Nickel (Ni), Rubidium (Rb), Silica (SiO2), Sulfate (SO4), Zinc (Zn), Cations, Anions, Reported total dissolved solids, Salinity, Charge balance, Isotopic composition of hydrogen (Delta 2H), Isotopic composition of oxygen in water (Delta 18O H2O), Oxygen shift, Digitizer comment. Gas chemistry data was digitized for 12 samples. Reported attributes include: Sample name, Type, State, County, Latitude, Longitude, Location resolution, Location error, Total gas, Oxygen and argon (O2 + Ar), Ethane (C2H6), Methane (CH4), Carbon dioxide (CO2), Nitrogen (N2), Author comment, Digitizer comment. Data was digitized from Tables 1, 3, 4, 5, 7, 9, and 10. The following tables were not digitized: Table 2: age and lithology of the bedrock at each thermal spring. Table 6: the mole ratios of major to minor constituents of thermal springs. Table 8: the equilibrium states of reactions in the thermal springs. Table 11: measured temperatures and estimated reservoir temperatures for the thermal springs.

This dataset contains 8 data tables provided in .csv format that contain sample location data, whole-rock geochemical data, argon-argon geochronologic data, sulfur, oxygen, and hydrogen isotope data, and mineralogical data from shortwave infrared spectrography (SWIR) and X-ray diffraction (XRD) analyses collected from igneous rocks on Brokeoff and Maidu volcanoes, northeastern California, USA. The data table files are Sample_Location_Data.csv, Argon_Data.csv, Geochemistry_Data.csv, SWIR_Data.csv, Whole_Rock_XRD.csv, Clay_XRD.csv, Sulfur_Isotope.csv, and Oxygen_Hydrogen_Data.csv. Fields in the data tables are defined in 8 corresponding data dictionaries, Sample_Location_Data_Dictionary.csv, Argon_Data_Dictionary.csv, Geochemistry_Data_Dictionary.csv, Whole_Rock_XRD_Dictionary.csv, Clay_XRD_Data_Dicitonary.csv, Sulfur_Isotope_Data_Dictionary.csv, Oxygen_Hydrogen_Isotope_Data_Dictionary.csv, and SWIR_Data Dictionary.csv. Analytical techniques are described in AnalyticalTechniques.txt.

This dataset contains 8 data tables provided in .csv format that contain sample location data, whole-rock geochemical data, argon-argon geochronologic data, sulfur, oxygen, and hydrogen isotope data, and mineralogical data from shortwave infrared spectrography (SWIR) and X-ray diffraction (XRD) analyses collected from igneous rocks on Brokeoff and Maidu volcanoes, northeastern California, USA. The data table files are Sample_Location_Data.csv, Argon_Data.csv, Geochemistry_Data.csv, SWIR_Data.csv, Whole_Rock_XRD.csv, Clay_XRD.csv, Sulfur_Isotope.csv, and Oxygen_Hydrogen_Data.csv. Fields in the data tables are defined in 8 corresponding data dictionaries, Sample_Location_Data_Dictionary.csv, Argon_Data_Dictionary.csv, Geochemistry_Data_Dictionary.csv, Whole_Rock_XRD_Dictionary.csv, Clay_XRD_Data_Dicitonary.csv, Sulfur_Isotope_Data_Dictionary.csv, Oxygen_Hydrogen_Isotope_Data_Dictionary.csv, and SWIR_Data Dictionary.csv. Analytical techniques are described in AnalyticalTechniques.txt.

Surface water, springs and wells in Pinnacles National Park (San Benito and Monterey Counties, CA) were sampled in the Fall of 2016 and Spring of 2017. Field parameters such as in situ pH, TDS/conductivity, and temperature were assessed. GPS coordinates for all samples were taken. Comprehensive groundwater chemistry, including major and minor elements, alkalinity, nutrients (and other parameters), Sr isotopes and REE concentrations, was analyzed at the National Water Quality Lab, USGS, Denver CO; and in USGS labs in Menlo Park, CA. One field visit on 8/20/2017 was made to obtain rock samples from the volcanic and sedimentary rocks in and around the park, which were digested and analyzed for whole rock chemistry (XRF, OES, ICP MS) by the Analytical Chemistry Lab (Mineral Resources Program, USGS, Denver CO). Sr isotopes for these samples were analyzed in the Menlo Park Metal Isotope Lab at the USGS. Precipitation was collected in a bulk collector during the winter of 2016-2017 and the chemistry and Sr isotopes of bulk samples was analyzed by ICP-MS or TIMS at the USGS Metal Isotope Lab in Menlo Park, CA.

Surface water, springs and wells in Pinnacles National Park (San Benito and Monterey Counties, CA) were sampled in the Fall of 2016 and Spring of 2017. Field parameters such as in situ pH, TDS/conductivity, and temperature were assessed. GPS coordinates for all samples were taken. Comprehensive groundwater chemistry, including major and minor elements, alkalinity, nutrients (and other parameters), Sr isotopes and REE concentrations, was analyzed at the National Water Quality Lab, USGS, Denver CO; and in USGS labs in Menlo Park, CA. One field visit on 8/20/2017 was made to obtain rock samples from the volcanic and sedimentary rocks in and around the park, which were digested and analyzed for whole rock chemistry (XRF, OES, ICP MS) by the Analytical Chemistry Lab (Mineral Resources Program, USGS, Denver CO). Sr isotopes for these samples were analyzed in the Menlo Park Metal Isotope Lab at the USGS. Precipitation was collected in a bulk collector during the winter of 2016-2017 and the chemistry and Sr isotopes of bulk samples was analyzed by ICP-MS or TIMS at the USGS Metal Isotope Lab in Menlo Park, CA.

Results from discrete multi-GAS surveys are compiled herein. Gas composition data were obtained using portable multi-GAS instruments that record H2O, CO2, SO2, and H2S gas mixing ratios, GPS coordinates, and pressure and temperature data at 1Hz. Initial surveys were completed in 2017 at East Lake hot springs and Paulina hot springs. In response to reports of anomalous degassing in the summer of 2020 more extensive multi-GAS surveys were completed around Newberry caldera. In 2020 the instruments' CO2, SO2, and H2S sensor responses were verified in the field with portable gas standards; in 2017 the instrument was lab-calibrated only. The collection and processing of multi-GAS data have been discussed in Gunawan et al. (2017) and Lewicki et al. (2017). Definitions of monitored features and any abbreviations are provided in the "Definitions" file found on the parent directory of this release. References Gunawan, H., Caudron, C., Pallister, J., Primulyana, S., Christenson, B., Mccausland, W., Van Hinsberg, V., Lewicki, J., Rouwet, D., Kelly, P., Kern, C., Werner, C., Johnson, J.B., Utami, S.B., Syahbana, D.K., Saing, U., Suparjan, Purwanto, B.H., Sealing, C., Cruz, M.M., Maryanto, S., Bani, P., Laurin, A., Schmid, A., Bradley, K., Agung Nandaka, I.G.M., Hendrasto, M., 2017. New insights into Kawah Ijen’s volcanic system from the wet volcano workshop experiment, Geological Society Special Publication. https://doi.org/10.1144/SP437.7 Lewicki, J.L., Kelly, P.J., Bergfeld, D., Vaughan, R.G., Lowenstern, J.B., 2017. Monitoring gas and heat emissions at Norris Geyser Basin, Yellowstone National Park, USA based on a combined eddy covariance and Multi-GAS approach. J. Volcanol. Geotherm. Res. https://doi.org/10.1016/j.jvolgeores.2017.10.001

Results from discrete multi-GAS surveys are compiled herein. Gas composition data were obtained using portable multi-GAS instruments that record H2O, CO2, SO2, and H2S gas mixing ratios, GPS coordinates, and pressure and temperature data at 1Hz. Initial surveys were completed in 2017 at East Lake hot springs and Paulina hot springs. In response to reports of anomalous degassing in the summer of 2020 more extensive multi-GAS surveys were completed around Newberry caldera. In 2020 the instruments' CO2, SO2, and H2S sensor responses were verified in the field with portable gas standards; in 2017 the instrument was lab-calibrated only. The collection and processing of multi-GAS data have been discussed in Gunawan et al. (2017) and Lewicki et al. (2017). Definitions of monitored features and any abbreviations are provided in the "Definitions" file found on the parent directory of this release. References Gunawan, H., Caudron, C., Pallister, J., Primulyana, S., Christenson, B., Mccausland, W., Van Hinsberg, V., Lewicki, J., Rouwet, D., Kelly, P., Kern, C., Werner, C., Johnson, J.B., Utami, S.B., Syahbana, D.K., Saing, U., Suparjan, Purwanto, B.H., Sealing, C., Cruz, M.M., Maryanto, S., Bani, P., Laurin, A., Schmid, A., Bradley, K., Agung Nandaka, I.G.M., Hendrasto, M., 2017. New insights into Kawah Ijen’s volcanic system from the wet volcano workshop experiment, Geological Society Special Publication. https://doi.org/10.1144/SP437.7 Lewicki, J.L., Kelly, P.J., Bergfeld, D., Vaughan, R.G., Lowenstern, J.B., 2017. Monitoring gas and heat emissions at Norris Geyser Basin, Yellowstone National Park, USA based on a combined eddy covariance and Multi-GAS approach. J. Volcanol. Geotherm. Res. https://doi.org/10.1016/j.jvolgeores.2017.10.001

Bulk organic geochemistry data were determined on one to five cm subsamples of sediment push cores collected from the Escanaba Trough during May to June 2022. These data include percent total organic carbon (percent TOC ), total nitrogen (percent TN), carbon to nitrogen ratios (C/N), stable carbon isotope ratios (d13C), stable nitrogen isotope ratios (d15N), radiocarbon values (D14C), and grain size (mean phi). Location information (for example , latitude, longitude, and depth) is also reported.