Geologic field-trip guide to the Lassen segment of the Cascades Arc, northern California

Clynne, Michael A.; Muffler, L. J. Patrick

doi:10.3133/sir20175022k2

Cited by 8 publications

(14 citation statements)

References 29 publications

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“…1A). The majority of Dome C collapsed ~350 years ago (Clynne and Muffler, 2017), leaving a semi-spherical collapse scar and an avalanche deposit called Chaos Jumbles (Fig. 1A).…”

Section: Methodsmentioning

confidence: 99%

Hydrothermal alteration can result in pore pressurization and volcano instability

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Baumann

Gilg

et al. 2021

Geology

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The collapse of a volcanic flank can be destructive and deadly. Hydrothermal alteration is common to volcanoes worldwide and is thought to promote volcano instability by decreasing rock strength. However, some laboratory studies have shown that not all alteration reduces rock strength. Our new laboratory data for altered rhyodacites from Chaos Crags (Lassen volcanic center, California, USA) show that pore- and crack-filling mineral precipitation can reduce porosity and permeability and increase strength, Young’s modulus, and cohesion. A significant reduction in permeability, by as much as four orders of magnitude, will inhibit fluid circulation and create zones of high pore fluid pressure. We explored the consequences of pore fluid pressurization on volcano stability using large-scale numerical modeling. Upscaled physical and mechanical properties for hydrothermally altered rocks were used as input parameters in our modeling. Results show that a high-pore-pressure zone within a volcano increases volcano deformation and that increasing the size of this zone increases the observed deformation. Hydrothermal alteration associated with mineral precipitation, and increases to rock strength, can therefore promote pore pressurization and volcano deformation, increasing the likelihood of volcano spreading, flank collapses, and phreatic/phreatomagmatic explosions. We conclude that porosity-decreasing alteration, explored here, and porosity-increasing alteration can both promote volcano instability and collapse, but by different mechanisms. Hydrothermal alteration should therefore be monitored at volcanoes worldwide and incorporated into hazard assessments.

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“…1A). The majority of Dome C collapsed ~350 years ago (Clynne and Muffler, 2017), leaving a semi-spherical collapse scar and an avalanche deposit called Chaos Jumbles (Fig. 1A).…”

Section: Methodsmentioning

confidence: 99%

Hydrothermal alteration can result in pore pressurization and volcano instability

Heap

Baumann

Gilg

et al. 2021

Geology

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“…Center in California, USA) was sampled from the Chaos Jumbles deposit (about 2 km from the volcano summit), a cold-rock avalanche deposit resulting from the collapse of Dome C about 350 years ago (Clynne and Muffler, 2017;Ryan et al, 2020). The rhyodacite has a porphyritic texture containing phenocrysts of predominantly plagioclase and potassium feldspar within a microcrystalline groundmass (Figure 2a; Ryan et al, 2020).…”

Section: Laboratory Samples and Experimentsmentioning

confidence: 99%

The tensile strength of volcanic rocks: Experiments and models

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Wadsworth

Heng

et al. 2021

Journal of Volcanology and Geothermal Research

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“…Geochemical groups are (1) calc-alkaline rocks or (2) low-potassium olivine tholeiite rocks. Calc-alkaline magmas, linked to arc volcanism, have high viscosity (Manga 1997;Lyle 2000;Manga 2001;Harris 2013;Muffler and Clynne 2015;Clynne and Muffler 2017; Fig. 3) and form scoria cones, steep-sided lava cones and broad shield volcanos, all with high aspect ratios and limited lateral extents (Clynne and Muffler 2010;Muffler and Clynne 2015;Clynne and Muffler 2017).…”

Section: Lava-flow Geochemistry Cooling and Geomorphic Formmentioning

confidence: 99%

“…Calc-alkaline magmas, linked to arc volcanism, have high viscosity (Manga 1997;Lyle 2000;Manga 2001;Harris 2013;Muffler and Clynne 2015;Clynne and Muffler 2017; Fig. 3) and form scoria cones, steep-sided lava cones and broad shield volcanos, all with high aspect ratios and limited lateral extents (Clynne and Muffler 2010;Muffler and Clynne 2015;Clynne and Muffler 2017). Lowpotassium olivine tholeiite magmas, associated with crustal extension, have low viscosity and produce widespread low-relief, valley-filling, sheet-flows from low, commonly inconspicuous vents (Fig.…”

Section: Lava-flow Geochemistry Cooling and Geomorphic Formmentioning

confidence: 99%

Effects of structure and volcanic stratigraphy on groundwater and surface water flow: Hat Creek basin, California, USA

et al. 2022

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Hydrogeologic systems in the southern Cascade Range in California (USA) develop in volcanic rocks where morphology, stratigraphy, extensional structures, and attendant basin geometry play a central role in groundwater flow paths, groundwater/surface-water interactions, and spring discharge locations. High-volume springs (greater than 3 m3/s) flow from basin-filling (<800 ka) volcanic rocks in the Hat Creek and Fall River tributaries and contribute approximately half of the average annual flow of the Pit River, the largest tributary to Shasta Lake. A hydrogeologic conceptual framework is constructed for the Hat Creek basin combining new geologic mapping, water-well lithologic logs, a database of active faults, LiDAR mapping of faults and volcanic landforms, streamflow measurements and airborne thermal infrared remote sensing of stream temperature. These data are used to integrate the geologic structure and the volcanic and volcaniclastic stratigraphy to create a three-dimensional interpretation of the hydrogeology in the basin. Two large streamflow gains from focused groundwater discharge near Big Spring and north of Sugarloaf Peak result from geologic barriers that restrict lateral groundwater flow and force water into Hat Creek. The inferred groundwater-flow barriers divide the aquifer system into at least three leaky compartments. The two downstream compartments lose streamflow in the upstream reaches (immediately downstream of the groundwater-flow barriers) and gain in downstream reaches with the greatest inflows immediately upstream of the barriers.

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Geologic field-trip guide to the Lassen segment of the Cascades Arc, northern California

Abstract: Cover: Photograph looking southwest from Emigrant Pass towards Lassen Peak (27±1 ka) in the center and Crescent Crater (236±1 ka) on the right.

Cited by 8 publications

References 29 publications

Hydrothermal alteration can result in pore pressurization and volcano instability

Hydrothermal alteration can result in pore pressurization and volcano instability

The tensile strength of volcanic rocks: Experiments and models

Effects of structure and volcanic stratigraphy on groundwater and surface water flow: Hat Creek basin, California, USA

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