S. Ingebritsen - Academia.edu (original) (raw)

Papers by S. Ingebritsen

ABSTRACT A unique opportunity for studying carbon exchange between the deep earth and the surface... more ABSTRACT A unique opportunity for studying carbon exchange between the deep earth and the surface exists at Mammoth Mountain in eastern California, where mantle-derived carbon dioxide has leaked through soils, springs, and fumaroles for decades, if not centuries. An estimated 3.5 × 10E9 kg of CO2 has escaped in the past 20 years. A long-term program of geochemical monitoring of gas at numerous sites reveals a consistent chemical and isotopic signature indicative of a large, well-mixed, CO2-rich gas reservoir residing within a few kilometers of the surface. Leakage of CO2 increases when the low-permeability seal capping the gas reservoir fails due to critical build-up of fluid-pressure, magma intrusion, and/or tectonic earthquakes. The high CO2 efflux at Mammoth Mountain has caused human fatalities, ecosystem disturbance, acidification of local water supplies, and raises the specter of CO2-rich gas explosions. The USGS Volcano Hazards Program recently launched an integrated geochemical, geophysical, hydrologic, and biologic research project aimed at holistic understanding of the origin, transport, and impact of magmatic carbon dioxide, with Mammoth Mountain as a natural, outdoor laboratory. Key elements of the project include: (I) Lithosphere Studies: Experimental investigation of deep, CO2-rich degassing of basaltic magmas, spatial-temporal analysis of fluid-driven earthquakes, and modeling of dynamic permeability provide insight into the origin and transport of CO2-rich fluids. (II) Hydrosphere/Atmosphere Studies: Tracking the concentration and geochemistry of surface exhalations through fumarole and spring sampling, soil efflux measurements, and 14C depletion in tree cores provide characteristics of the shallow gas reservoir and a time-series record of total CO2 efflux. (III) Biosphere Studies: Field-based studies and greenhouse experiments investigate the effect of elevated CO2 on biogeochemical cycles, soil nutrient levels, and changes in vegetation and microbial communities. We expect discipline-specific results from (I, II) to advance our understanding of the dynamics of restless volcanoes and deep crustal magma systems, and from (II, III) to help predict ecosystem stress induced by global climate change, CO2 sequestration, and enhanced geothermal production. Ultimately, results from (III) may circle back into advances in (I) whereby past episodes of magma intrusion and volcanic gas release are recognized by ecosystem disturbance, independent of traditional monitoring data.

2014 AGU Fall Meeting, Dec 17, 2014

AGU Fall Meeting Abstracts, Dec 1, 2019

Journal of Geophysical Research, 2009

Ground surface displacement (GSD) in large calderas is often interpreted as resulting from magma ... more Ground surface displacement (GSD) in large calderas is often interpreted as resulting from magma intrusion at depth. Recent advances in geodetic measurements of GSD, notably interferometric synthetic aperture radar, reveal complex and multifaceted deformation patterns that often require complex source models to explain the observed GSD. Although hydrothermal fluids have been discussed as a possible deformation agent, very few quantitative studies addressing the effects of multiphase flow on crustal mechanics have been attempted. Recent increases in the power and availability of computing resources allow robust quantitative assessment of the complex time-variant thermal interplay between aqueous fluid flow and crustal deformation. We carry out numerical simulations of multiphase (liquid-gas), multicomponent (H 2 O-CO 2) hydrothermal fluid flow and poroelastic deformation using a range of realistic physical parameters and processes. Hydrothermal fluid injection, circulation, and gas formation can generate complex, temporally and spatially varying patterns of GSD, with deformation rates, magnitudes, and geometries (including subsidence) similar to those observed in several large calderas. The potential for both rapid and gradual deformation resulting from magma-derived fluids suggests that hydrothermal fluid circulation may help explain deformation episodes at calderas that have not culminated in magmatic eruption.

Economic Geology, 2012

Hydrothermal ore deposits represent a convergence of fluid flow, thermal energy, and solute flux ... more Hydrothermal ore deposits represent a convergence of fluid flow, thermal energy, and solute flux that is hydrogeologically unusual. From the hydrogeologic perspective, hydrothermal ore deposition represents a complex coupled-flow problem-sufficiently complex that physically rigorous description of the coupled thermal (T), hydraulic (H), mechanical (M), and chemical (C) processes (THMC modeling) continues to challenge our computational ability. Though research into these coupled behaviors has found only a limited subset to be quantitatively tractable, it has yielded valuable insights into the workings of hydrothermal systems in a wide range of geologic environments including sedimentary, metamorphic, and magmatic. Examples of these insights include the quantification of likely driving mechanisms, rates and paths of fluid flow, ore-mineral precipitation mechanisms, longevity of hydrothermal systems, mechanisms by which hydrothermal fluids acquire their temperature and composition, and the controlling influence of permeability and other rock properties on hydrothermal fluid behavior. In this communication we review some of the fundamental theory needed to characterize the physical hydrogeology of hydrothermal systems and discuss how this theory has been applied in studies of Mississippi Valley-type, tabular uranium, porphyry, epithermal, and mid-ocean ridge ore-forming systems. A key limitation in the computational state-of-the-art is the inability to describe fluid flow and transport fully in the many ore systems that show evidence of repeated shear or tensional failure with associated dynamic variations in permeability. However, we discuss global-scale compilations that suggest some numerical constraints on both mean and dynamically enhanced crustal permeability. Principles of physical hydrogeology can be powerful tools for investigating hydrothermal ore formation and are becoming increasingly accessible with ongoing advances in modeling software.

Earth and Planetary Science Letters, 2005

In the upper crust, where hydraulic gradients are typically Ͻ1 MPa km Ϫ1 , advective heat transpo... more In the upper crust, where hydraulic gradients are typically Ͻ1 MPa km Ϫ1 , advective heat transport is often effective for permeabilities k Ն 10 Ϫ16 m 2 and advective mass (solute) transport for k Ն 10 Ϫ20 m 2. Regional-scale analyses of coupled groundwater flow and heat transport in the upper crust typically infer permeabilities in the range of 10 Ϫ17 to 10 Ϫ14 m 2 , so that heat advection is sometimes significant and solute advection should nearly always be significant. Analyses of metamorphic systems suggest that a geochemically significant level of permeability can exist to the base of the crust. In active metamorphic systems in the mid to lower crust, where vertical hydraulic gradients are likely Ͼ10 MPa km Ϫ1 , the mean permeabilities required to accommodate the estimated metamorphic fluid fluxes decrease from ϳ10 Ϫ16 m 2 to ϳ10 Ϫ18 m 2 between 5-and 12-km depth. Below ϳ12 km, which broadly corresponds to the brittle-plastic transition, mean k is effectively independent of depth at ϳ10 Ϫ18.5Ϯ1 m 2. Consideration of the permeability values inferred from thermal modeling and metamorphic fluxes suggests a quasi-exponential decay of permeability with depth of log k Ϸ Ϫ3.2 log z Ϫ 14, where k is in meters squared and z is in kilometers. At mid to lower crustal depths this curve lies just below the threshold value for significant advection of heat. Such conditions may represent an optimum for metamorphism, allowing the maximum transport of fluid and solute mass that is possible without advective cooling.

Water Resources Research, 1996

Isotope tracer methods were used to determine flow paths, recharge areas, and relative age for gr... more Isotope tracer methods were used to determine flow paths, recharge areas, and relative age for groundwater in the Kilauea volcano area of the Island of Hawaii. A network of up to 66 precipitation collectors was emplaced in the study area and sampled twice yearly for a 3-year period. Stable isotopes in rainfall show three distinct isotopic gradients with elevation, which are correlated with trade wind, rain shadow, and highelevation climatological patterns. Temporal variations in precipitation isotopes are controlled more by the frequency of storms than by seasonal temperature fluctuations. Results from this study suggest that (1) sampling network design must take into account areal variations in rainfall patterns on islands and in continental coastal areas and (2) isotope/elevation gradients on other tropical islands may be predictable on the basis of similar climatology. Groundwater was sampled yearly in coastal springs, wells, and a few high-elevation springs. Areal contrasts in groundwater stable isotopes and tritium indicate that the volcanic rift zones compartmentalize the regional groundwater system, isolating the groundwater south of Kilauea's summit and rift zones.

Water Science and Technology Library, 2003

Water Resources Research, 1998

Interferometric synthetic aperture radar (InSAR) has great potential to detect and quantify land ... more Interferometric synthetic aperture radar (InSAR) has great potential to detect and quantify land subsidence caused by aquifer system compaction. InSAR maps with high spatial detail and resolution of range displacement (Ϯ10 mm in change of land surface elevation) were developed for a groundwater basin (ϳ10 3 km 2) in Antelope Valley, California, using radar data collected from the ERS-1 satellite. These data allow comprehensive comparison between recent (1993-1995) subsidence patterns and those detected historically (1926-1992) by more traditional methods. The changed subsidence patterns are generally compatible with recent shifts in land and water use. The InSARdetected patterns are generally consistent with predictions based on a coupled model of groundwater flow and aquifer system compaction. The minor inconsistencies may reflect our imperfect knowledge of the distribution and properties of compressible sediments. When used in conjunction with coincident measurements of groundwater levels and other geologic information, InSAR data may be useful for constraining parameter estimates in simulations of aquifer system compaction.

Remote Sensing of Environment, 1986

Our goal is to exhibit multispectral time-difference data in factored form so as to emphasize sig... more Our goal is to exhibit multispectral time-difference data in factored form so as to emphasize signal differences, assumed to be spatially structured, and isolate noise, which is assumed to be spatially unstructured. The method we use is a variant of the MAF procedure (Min/Max ...

Journal of Volcanology and Geothermal Research, 2010

Hydrothermal heat discharge in the Cascade Range includes the heat discharged by thermal springs,... more Hydrothermal heat discharge in the Cascade Range includes the heat discharged by thermal springs, by "slightly thermal" springs that are only a few degrees warmer than ambient temperature, and by fumaroles. Thermal-spring heat discharge is calculated on the basis of chloride-flux measurements and geothermometer temperatures and totals~240 MW in the U.S. part of the Cascade Range, excluding the transient post-1980 discharge at Mount St. Helens (~80 MW as of 2004-5). Heat discharge from "slightly thermal" springs is based on the degree of geothermal warming (after correction for gravitational potential energy effects) and totals~660 MW. Fumarolic heat discharge is calculated by a variety of indirect and direct methods and totals~160 MW, excluding the transient mid-1970s discharge at Mount Baker (~80 MW) and transient post-1980 discharge at Mount St. Helens (N 230 MW as of 2005). Other than the pronounced transients at Mount St. Helens and Mount Baker, hydrothermal heat discharge in the Cascade Range appears to be fairly steady over a~25-year period of measurement. Of the total of~1050 MW of "steady" hydrothermal heat discharge identified in the U.S. part of the Cascade Range, less than 50 MW occurs north of latitude 45°15′ N (~0.1 MW per km arc length from 45°15′ to 49°N). Much greater rates of hydrothermal heat discharge south of 45°15′N (~1.7 MW per km arc length from 40°to 45°15′N) may reflect the influence of Basin and Range-style extensional tectonics (faulting) that impinges on the Cascades as far north as Mount Jefferson but is not evident farther north.

Journal of Volcanology and Geothermal Research, 2001

We compiled time series of hydrothermal discharge consisting of 3593 chloride- or heat-flux measu... more We compiled time series of hydrothermal discharge consisting of 3593 chloride- or heat-flux measurements from 24 sites in the Yellowstone region, the northern Oregon Cascades, Lassen Volcanic National Park and vicinity, and Long Valley, California. At all of these sites the hydrothermal phenomena are believed to be as yet unaffected by human activity, though much of the data collection was