Geology topics

S. E. Ingebritsen

Publications and source records attributed to S. E. Ingebritsen.

At least 19 recordsLinked to original sources

USGS2012

The hydrothermal system at Newberry Volcano, Oregon

Results of recent geological and geophysical studies at Newberry Volcano have been incorporated into conceptual and numerical models of a magma-based hydrothermal system. Numerical simulations begin with emplacement of a small magma body, the presumed source of silicic eruptions at Newberry that began about 10,000 B.P., into a thermal regime representing 100,000 years of cooling of a large underlying intrusion. Simulated flow patterns and thermal histories for three sets of hypothetical permeability values are compatible with data from four geothermal drill holes on the volcano. Meteoric recharge cools the caldera-fill deposits, but thermal water moving up a central conduit representing a permeable volcanic vent produces temperatures close to those observed in drill holes within the caldera. Meteoric recharge from the caldera moves down the flanks and creates a near-isothermal zone that extends several hundred meters below the water table, producing temperature profiles similar to those observed in drill holes on the flanks. The temperatures observed in drill holes on the flanks are not influenced by the postulated Holocene magma body. The elevated temperature gradients measured in the lower portions of these holes may be related to the cumulative effect of older intrusions. The models also indicate that meteoric recharge to the deep hydrothermal system probably originates within or near the caldera. Relatively low fluid velocities at depth suggest that at least a significant fraction of the thermal fluid may be very old.

Journal of Geophysical Research Solid Earth↗

USGS2012

Vapor-dominated zones within hydrothermal systems: Evolution and natural state

Three conceptual models illustrate the range of hydrothermal systems in which vapor-dominated conditions are found. The first model (model I) represents a system with an extensive near-vaporstatic vapor-dominated zone and limited liquid throughflow and is analogous to systems such as The Geysers, California. Such systems can evolve within low-permeability barriers without changes in boundary conditions or rock properties, given an adequate supply of heat. Their scarcity in nature may be due to the need for a long-lived, potent heat source and for a low-permeability aureole that remains intact for significant lengths of time. Models II and III represent systems with significant liquid throughflow and include steam-heated discharge features at higher elevations and high-chloride springs at lower elevations, connected to and fed by a single circulation system at depth. In model II, as in model I, the vapor-dominated zone has a near-vaporstatic vertical pressure gradient and is generally underpressured with respect to local hydrostatic pressure. The vapor-dominated zone in model III is quite different, in that phase separation takes place at pressures close to local hydrostatic and the overall pressure gradient is near hydrostatic. A relatively large number of high-temperature systems in regions of moderate to great topographic relief are similar to either model II or model III; however, in most cases there are insufficient data to establish a single preferred model.

Journal of Geophysical Research Solid Earth↗

USGS2011

Geology for a changing world 2010-2020-Implementing the U.S. Geological Survey science strategy

This report describes a science strategy for the geologic activities of the U.S. Geological Survey (USGS) for the years 2010-2020. It presents six goals with accompanying strategic actions and products that implement the science directions of USGS Circular 1309, 'Facing Tomorrow's Challenges-U.S. Geological Survey Science in the Decade 2007-2017.' These six goals focus on providing the geologic underpinning needed to wisely use our natural resources, understand and mitigate hazards and environmental change, and understand the relationship between humans and the environment. The goals emphasize the critical role of the USGS in providing long-term research, monitoring, and assessments for the Nation and the world. Further, they describe measures that must be undertaken to ensure geologic expertise and knowledge for the future. The natural science issues facing today's world are complex and cut across many scientific disciplines. The Earth is a system in which atmosphere, oceans, land, and life are all connected. Rocks and soils contain the answers to important questions about the origin of energy and mineral resources, the evolution of life, climate change, natural hazards, ecosystem structures and functions, and the movements of nutrients and toxicants. The science of geology has the power to help us understand the processes that link the physical and biological world so that we can model and forecast changes in the system. Ensuring the success of this strategy will require integration of geological knowledge with the other natural sciences and extensive collaboration across USGS science centers and with partners in Federal, State, and local agencies, academia, industry, nongovernmental organizations and, most importantly, the American public. The first four goals of this report describe the scientific issues facing society in the next 10 years and the actions and products needed to respond to these issues. The final two goals focus on the expertise and infrastructure needed to ensure the long-term sustainability of the geological sciences in the USGS. The ultimate goal of USGS science and of the strategy laid out in this document is to contribute to the development of a sustainable society that operates in harmony with the Earth systems that society depends upon. As we begin the second decade of the 21st century, our Nation faces growing challenges in resource availability, climate and environmental change, and natural hazards. Meeting these challenges will require strong collaboration across the natural and social sciences and extensive partnerships with both the public and private sectors. The six goals described in this document represent a mix of scientific focus areas and operational necessities that together provide a comprehensive roadmap for USGS geologic science to effectively contribute to the USGS mission, providing science for a changing world.

Circular↗

USGS2010

Numerical simulation of magmatic hydrothermal systems

The dynamic behavior of magmatic hydrothermal systems entails coupled and nonlinear multiphase flow, heat and solute transport, and deformation in highly heterogeneous media. Thus, quantitative analysis of these systems depends mainly on numerical solution of coupled partial differential equations and complementary equations of state (EOS). The past 2 decades have seen steady growth of computational power and the development of numerical models that have eliminated or minimized the need for various simplifying assumptions. Considerable heuristic insight has been gained from process-oriented numerical modeling. Recent modeling efforts employing relatively complete EOS and accurate transport calculations have revealed dynamic behavior that was damped by linearized, less accurate models, including fluid property control of hydrothermal plume temperatures and three-dimensional geometries. Other recent modeling results have further elucidated the controlling role of permeability structure and revealed the potential for significant hydrothermally driven deformation. Key areas for future reSearch include incorporation of accurate EOS for the complete H2O-NaCl-CO2 system, more realistic treatment of material heterogeneity in space and time, realistic description of large-scale relative permeability behavior, and intercode benchmarking comparisons. Copyright 2010 by the American Geophysical Union.

Reviews of Geophysics↗

USGS2010

Hydrothermal heat discharge in the Cascade Range, northwestern United States

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 (>. 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. ?? 2010.

Journal of Volcanology and Geothermal Research↗

USGS2009

Numerical models of caldera deformation: Effects of multiphase and multicomponent hydrothermal fluid flow

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 2O-CO2) 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.

Journal of Geophysical Research B: Solid Earth↗

USGS2008

Permeability of continental crust influenced by internal and external forcing

The permeability of continental crust is so highly variable that it is often considered to defy systematic characterization. However, despite this variability, some order has been gleaned from globally compiled data. What accounts for the apparent coherence of mean permeability in the continental crust (and permeability–depth relations) on a very large scale? Here we argue that large‐scale crustal permeability adjusts to accommodate rates of internal and external forcing. In the deeper crust, internal forcing – fluxes induced by metamorphism, magmatism, and mantle degassing – is dominant, whereas in the shallow crust, external forcing – the vigor of the hydrologic cycle – is a primary control. Crustal petrologists have long recognized the likelihood of a causal relation between fluid flux and permeability in the deep, ductile crust, where fluid pressures are typically near‐lithostatic. It is less obvious that such a relation should pertain in the relatively cool, brittle upper crust, where near‐hydrostatic fluid pressures are the norm. We use first‐order calculations and numerical modeling to explore the hypothesis that upper‐crustal permeability is influenced by the magnitude of external fluid sources, much as lower‐crustal permeability is influenced by the magnitude of internal fluid sources. We compare model‐generated permeability structures with various observations of crustal permeability.

Geofluids↗

USGS2008

A quantitative analysis of the Lassen hydrothermal system, north central California

Our conceptual model of the Lassen system is termed a liquid-dominated hydrothermal system with a parasitic vapor-dominated zone. The essential feature of this model is that steam and steam-heated discharge at relatively high altitudes in Lassen Volcanic National Park (LVNP) and liquid discharge with high chloride concentrations at relatively low altitudes outside LVNP are both fed by an upflow of high-enthalpy two-phase fluid within the Park. Liquid flows laterally away from the upflow area toward the areas of high-chloride discharge, and steam rises through a vapor-dominated zone to feed the steam and steam-heated features. Numerical simulations show that several conditions are necessary for the development of this type of system, including (1) large-scale topographic relief; (2) an initial period of convective heating within an upflow zone followed by (3) a change in hydrologic or geologic conditions that initiates drainage of liquid from portions of the upflow zone; and (4) low-permeability barriers that inhibit the movement of cold water into the vapor zone. Simulations of thermal fluid withdrawal south of LVNP, carried out in order to determine the effects of such withdrawal on portions of the hydrothermal system within the Park, generally showed decreases in pressure and liquid saturation beneath the vapor zone which resulted in temporary increases and subsequent decreases in the rate of upflow of steam. A generalized production-injection scenario that could mitigate the effects of development on both the high-chloride and steam-fed features was identified.

California↗

USGS2005

Seasonal seismicity at western United States volcanic centers

We examine 20-yr data sets of seismic activity from 10 volcanic areas in the western United States for annual periodic signals (seasonality), focusing on large calderas (Long Valley caldera and Yellowstone) and stratovolcanoes (Cascade Range). We apply several statistical methods to test for seasonality in the seismic catalogs. In 4 of the 10 regions, statistically significant seasonal modulation of seismicity (> 90% probability) occurs, such that there is an increase in the monthly seismicity during a given portion of the year. In five regions, seasonal seismicity is significant in the upper 3 km of the crust. Peak seismicity occurs in the summer and autumn in Mt. St. Helens, Hebgen Lake/Madison Valley, Yellowstone Lake, and Mammoth Mountain. In the eastern south moat of Long Valley caldera (LVC) peak seismicity occurs in the winter and spring. We quantify the possible external forcing mechanisms that could modulate seasonal seismicity. Both snow unloading and groundwater recharge can generate large stress changes of > 5 kPa at seismogenic depths and may thus contribute to seasonality. ?? 2005 Elsevier B.V. All rights reserved.

Earth and Planetary Science Letters↗

USGS2005

Ongoing hydrothermal heat loss from the 1912 ash-flow sheet, Valley of Ten Thousand Smokes, Alaska

The June 1912 eruption of Novarupta filled nearby glacial valleys on the Alaska Peninsula with ash-flow tuff (ignimbrite), and post-eruption observations of thousands of steaming fumaroles led to the name ‘Valley of Ten Thousand Smokes’ (VTTS). By the late 1980s most fumarolic activity had ceased, but the discovery of thermal springs in mid-valley in 1987 suggested continued cooling of the ash-flow sheet. Data collected at the mid-valley springs between 1987 and 2001 show a statistically significant correlation between maximum observed chloride (Cl) concentration and temperature. These data also show a statistically significant decline in the maximum Cl concentration. The observed variation in stream chemistry across the sheet strongly implies that most solutes, including Cl, originate within the area of the VTTS occupied by the 1912 deposits. Numerous measurements of Cl flux in the Ukak River just below the ash-flow sheet suggest an ongoing heat loss of ∼250 MW. This represents one of the largest hydrothermal heat discharges in North America. Other hydrothermal discharges of comparable magnitude are related to heat obtained from silicic magma bodies at depth, and are quasi-steady on a multidecadal time scale. However, the VTTS hydrothermal flux is not obviously related to a magma body and is clearly declining. Available data provide reasonable boundary and initial conditions for simple transient modeling. Both an analytical, conduction-only model and a numerical model predict large rates of heat loss from the sheet 90 years after deposition.

Alaska↗

USGS2004

Magmatic intrusion west of Three Sisters, central Oregon, USA: The perspective from spring geochemistry

A geochemical investigation of springs near Three Sisters volcanoes was conducted in response to the detection of crustal uplift west of the peaks. Dilute, low-temperature springs near the center of uplift show 3 He/ 4 He ratios ≥7 R A ( R A is the ratio in air), and transport in total ∼16 MW of heat and ∼180 g/s of magmatic carbon (as CO 2 ). These anomalous conditions clearly reflect the influence of magma, but they seemingly predate the onset of the present uplift and derive from a previous event. Episodes of intrusion may thus be more common in this area than the age of eruptive vents would imply.

Geology↗

USGS2003

Variability in geyser eruptive timing and its causes: Yellowstone National Park

Field data from Upper Geyser Basin, Yellowstone, indicate that geyser frequency is less sensitive to elastic deformation than might be surmised from a review of the literature. Earth-tide influences are not identifiable in any of the geysers we monitored. Though atmospheric-pressure influences are observed, only long-period variations on the order of 5 mBars or greater seem to influence geyser frequency. Long-distance interconnections between geysers are common and add to the difficulty of identifying strain influences. Additional variations in geyser periodicity may be governed by the internal dynamics of the geysers rather than external influences.

Geophysical Research Letters↗

USGS2003

Implications of crustal permeability for fluid movement between terrestrial fluid reservoirs

A classic paper by Rubey [Geol. Soc. Amer. Bull 62 (1951) 1111] examined various hypotheses regarding the origin of sea water and concluded that the most likely hypothesis was volcanic outgassing, a view that was generally accepted by Earth scientists for the next several decades. More recent work suggests that the rate of subduction of water is much larger than the volcanic outgassing rate, lending support to hypotheses that either ocean volume has decreased with time, or that the imbalance is offset by continuous replenishment of water by cometary impacts. These alternatives are required in the absence of additional mechanisms for the return of water from subducting lithosphere to the Earth's surface. Our recent work on crustal permeability suggests a large capacity for water upflow through tectonically active continental crust, resulting in a heretofore-unrecognized degassing pathway that can accommodate the water-subduction rate. Escape of recycled water via delivery from the mantle through zones of active metamorphism eliminates the mass-balance argument for the loss of ocean volume or extraterrestrial sources. ?? 2003 Elsevier Science B.V. All rights reserved.

Conference Paper↗

USGS2003

Groundwater flow, heat transport, and water table position within volcanic edifices: Implications for volcanic processes in the Cascade Range

The position of the water table within a volcanic edifice has significant implications for volcano hazards, geothermal energy, and epithermal mineralization. We have modified the HYDROTHERM numerical simulator to allow for a free-surface (water table) upper boundary condition and a wide range of recharge rates, heat input rates, and thermodynamic conditions representative of continental volcano-hydrothermal systems. An extensive set of simulations was performed on a hypothetical stratovolcano system with unconfined groundwater flow. Simulation results suggest that the permeability structure of the volcanic edifice and underlying material is the dominant control on water table elevation and the distribution of pressures, temperatures, and fluid phases at depth. When permeabilities are isotropic, water table elevation decreases with increasing heat flux and increases with increasing recharge, but when permeabilities are anisotropic, these effects can be much less pronounced. Several conditions facilitate the ascent of a hydrothermal plume into a volcanic edifice: a sufficient source of heat and magmatic volatiles at depth, strong buoyancy forces, and a relatively weak topography-driven flow system. Further, the plume must be connected to a deep heat source through a pathway with a time-averaged effective permeability ???1 ?? 10-16 m2, which may be maintained by frequent seismicity. Topography-driven flow may be retarded by low permeability in the edifice and/or the lack of precipitation recharge; in the latter case, the water table may be relatively deep. Simulation results were compared with observations from the Quaternary stratovolcanoes along the Cascade Range of the western United States to infer hydrothermal processes within the edifices. Extensive ice caps on many Cascade Range stratovolcanoes may restrict recharge on the summits and uppermost flanks. Both the simulation results and limited observational data allow for the possibility that the water table beneath the stratovolcanoes is relatively deep.

Journal of Geophysical Research B: Solid Earth↗

USGS2002

Episodic thermal perturbations associated with groundwater flow: An example from Kilauea Volcano, Hawaii

Temperature measurements in deep drill holes on volcano summits or upper flanks allow a quantitative analysis of groundwater induced heat transport within the edifice. We present a new temperature-depth profile from a deep well on the summit of Kilauea Volcano, Hawaii, and analyze it in conjunction with a temperature profile measured 26 years earlier. We propose two groundwater flow models to interpret the complex temperature profiles. The first is a modified confined lateral flow model (CLFM) with a continuous flux of hydrothermal fluid. In the second, transient flow model (TFM), slow conductive cooling follows a brief, advective heating event. We carry out numerical simulations to examine the timescales associated with each of the models. Results for both models are sensitive to the initial conditions, and with realistic initial conditions it takes between 750 and 1000 simulation years for either model to match the measured temperature profiles. With somewhat hotter initial conditions, results are consistent with onset of a hydrothermal plume ∼550 years ago, coincident with initiation of caldera subsidence. We show that the TFM is consistent with other data from hydrothermal systems and laboratory experiments and perhaps is more appropriate for this highly dynamic environment. The TFM implies that volcano-hydrothermal systems may be dominated by episodic events and that thermal perturbations may persist for several thousand years after hydrothermal flow has ceased.

Hawaii↗

USGS2002

Diffuse fluid flux through orogenic belts: Implications for the world ocean

Fifty years ago a classic paper by W. W. Rubey [(1951) Geol. Soc. Am. Bull. 62, 1111-1148] examined various hypotheses regarding the origin of sea water and concluded that the most likely hypothesis was volcanic outgassing, a view that was generally accepted by earth scientists for the next several decades. More recent work suggests that the rate of subduction of water is much larger than the volcanic outgassing rate, lending support to hypotheses that either ocean volume has decreased with time, or that the imbalance is offset by continuous replenishment of water by cometary impacts. These alternatives are required in the absence of additional mechanisms for the return of water from subducting lithosphere to the Earth's surface. Our recent work on crustal permebility suggests a large capacity for water upflow through tectonically active continental crust, resulting in a heretofore unrecognized degassing pathway that can accommodate the waer subduction rate. Escape of recycled water via delivery from the mantle through zones of active metamorphism eliminates the mass-balance argument for the loss of ocean volume or extraterestrial sources.

Proceedings of the National Academy of Sciences of↗

USGS2001

Time-variation of hydrothermal discharge at selected sites in the Western United States: Implications for monitoring

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 driven by mandates to collect environmental-baseline data in acticipation of geothermal development. The time series average 19 years in length and some of the Yellowstone sites have been monitored intermittently for over 30 years. Many sites show strong seasonality but few show clear long-term trends, and at most sites statistically significant decadal-scale trends are absent. Thus, the data provide robust estimates of advective heat flow ranging from ~130 MW in the north-central Oregon Cascades to ~6100 MW in the Yellowstone region, and also document Yellowstone hydrothermal chloride and arsenic fluxes of 1740 and 15-20 g/s, respectively. The discharge time series show little sensitivity to regional tectonic events such as earthquakes or inflation/deflation cycles. Most long-term monitoring to date has focused on high-chloride springs and low-temperature fumaroles. The relative stability of these features suggests that discharge measurements done as part of volcano-monitoring programs should focus instead on high-temperature fumaroles, which may be more immediately linked to the magmatic heat source.

Journal of Volcanology and Geothermal Research↗

USGS2000

Delta subsidence in California: The sinking heart of the state

The Sacramento-San Joaquin River Delta of California once was a great tidal freshwater marsh blanketed by peat and peaty alluvium. Beginning in the late 1800s, levees were built along the stream channels, and the land thus protected from flooding was drained, cleared, and planted. Although the Delta is now an exceptionally rich agricultural area (over a $500 million crop value in 1993), its unique value is as a source of freshwater for the rest of the State. It is the heart of a massive north-to-south waterdelivery system. Much of this water is pumped southward for use in the San Joaquin Valley and elsewhere in central and southern California. The leveed tracts and islands help to protect water-export facilities in the southern Delta from saltwater intrusion by displacing water and maintaining favorable freshwater gradients. However, ongoing subsidence behind the levees reduces levee stability and, thus, threatens to degrade water quality in the massive north-to-south water-transfer system.

California↗