Reviews of Geophysics - 2014 - Hurwitz - Dynamics of the Yellowstone hydrothermal system

Dynamics of the Yellowstone Hydrothermal System

Abstract

• Yellowstone Plateau Volcanic Field (YPVF) features extensive seismicity, uplift, subsidence, and over 10,000 hydrothermal features (geyser, fumaroles, mud pots).

• Thermal waters' compositions come from mantle, crustal, meteoric sources, and water-gas-rock interactions.

• Hydrothermal system hosts diverse life forms utilizing inorganic energy sources.

• Historical research in Yellowstone dates back to the 1870s, with significant advancements over the past 25 years, enhancing our understanding of magmatic and hydrothermal processes.

Advances and Research Focus

• Refined geophysical imaging of magmatic systems.

• Characterized fluid sources and interactions, quantified heat and volatile fluxes.

• Role of thermophiles identified in geochemical cycles and linkages between hydrothermal activity and geological changes.

• Hydrothermal activity extended to Yellowstone Lake.

Introduction

• YPVF has produced three significant eruptions in the last 2.1 million years due to a mantle hot spot.

• Last eruption around 0.64 Ma formed the Yellowstone Caldera.

• Caldera characterized by uplift, subsidence, and significant thermal activity.

• Thermal waters vary in pH (1.5–10.0), chemistry influenced by underlying geology and external factors.

• Hydrothermal activity influences seismicity and deformation across various timescales.

Key Points

• State and knowledge of Yellowstone’s magma-hydrothermal system assessed.

• Advances stem from modern technology applications in research.

Research Motivations

Assessing Hazards

• Understanding hazards linked to hydrothermal activity is crucial.

Preservation of Unique Features

• Research aims at preservation by understanding variability in hydrothermal systems.

Uniqueness of Yellowstone

• Protected from geothermal energy exploration allows comprehensive undisturbed study.

• Characterization hampered by vast thermal features and seasonal access limitations due to snow/ice.

Major Questions Driving Research

• How do magmatic volatile emissions inform depth magma state?

• How are earthquake swarms linked to hydrothermal/magmatic activities?

• What are the control factors on geyser eruption behaviors?

• How do geochemical processes relate to microbial community interactions?

Advances and Research Directions

• Identifying links between hydrothermal systems and interactions with climate and tectonics.

• Establishing feedback loops in geothermal, magmatic, and tectonic processes is an ongoing research challenge.

Volcanic History and Magmatic System State

Formation of YPVF

• Formed from three significant eruptive cycles affecting Precambrian and Tertiary geological formations.

• Dominated by rhyolitic rock formations from explosive eruptions.

• Formation of large calderas and subsequent uplift observed, impacting hydrothermal feature distributions.

Characteristics of Yellowstone Caldera

• Covers an area of ~80 x 50 km filled with post-caldera rhyolitic lava.

• Active uplift and downward motion provides insights into the dynamics of surface deformation.

Seismicity and Deformation

Earthquake Patterns

• Thousands of small earthquakes occur annually in and near the Yellowstone Caldera.

• Clustered in swarms, primarily in relation to caldera inflation and associated geological changes.

• Historical data indicates migration patterns evolving with sea level changes.

Measuring Ground Surface Elevation

• Changes analyzed via leveling and GPS techniques since 1923 confirm repetitive deformation episodes.

• Differential uplift and subsidence documented using data across decades.

• Models suggest magma chamber dynamics beneath the caldera are critical to observed seismicity.

Hydrothermal Dynamics

Heat and Mass Transport

• Nearly all heat and much of the gas emerge from the underlying magmatic system through hydrothermal processes.

• Information on heat transport inferred mainly through geophysical and geochemical observations, indicating complex subsurface flow behavior.

The Chemical Dynamics of Hydrothermal Systems

• Hydrothermal fluids undergo transitions in mineralogy due to temperature and pressure changes.

• Interactions with surrounding geological features crucially shape thermal water chemistry.

Hydrothermal Activity Variance

Temporal Influences

• Seasonal changes in hydrology significantly contribute to variability in hydrothermal activity.

• External events (earthquakes, climate shifts) modulate system responses.

Geyser and Explosive Activity

• Geysers – critical to understanding hydrothermal dynamics due to their rarity and intricate functionalities.

• Notable historical eruptions and explosive events demonstrate the danger and scientific importance of monitoring hydrothermal dynamics.

• Research into geyser eruptive sequences provides insight into subsurface geology and hydrothermal stability.

Suggestions for Future Research

1. Enhance multidisciplinary studies for better process understanding.

2. Improve remote sensing technologies for monitoring hydrothermal changes.

3. Assess interactions between hydrothermal fluids and microbial actions.

4. Investigate the relationship between temperature and magmatic gas emissions.

5. Predict hydrothermal explosions through refined monitoring techniques.

Concluding Remarks

• The review outlines significant advancements over the past 25 years, emphasizing how modern technologies have amplified understanding of Yellowstone's dynamic hydrothermal system.

• Future research trajectories will rely on refined methods to elucidate the complex interplay between Yellowstone's geological processes.