Volcanology Commons^™

Geochemical And Petrological Observations Of The June Lake Basalt, Eastern California, Daniel Jacob Abel

Cal Poly Humboldt theses and projects

The June Lake basalt is a monogenetic cinder cone and 11-km-long lava flow in eastern California located ~10 km NW of the Long Valley caldera. The stratigraphic position of the June Lake basalt between Tahoe and Tioga glacial deposits suggests an eruption age of only ~20-45ka. This age places the June Lake Basalt among the youngest volcanic eruptions in the Long Valley-Mono Basin region, where volcanic activity spans from the late Pliocene to the Holocene. The goal of this study is to use field observations coupled with whole-rock and crystal geochemical analyses to investigate the magma source and pre-eruption magma …

The Effects Of A Microplate On Plume-Ridge Interactions: Constraints From Comparing Easter And Juan Fernandez Microplates In The Eastern Pacific Ocean, Katherine Ames, Jennifer Georgen

OES Faculty Publications

This study investigates the nature of plume-ridge interactions near a tectonic microplate using mantle Bouguer anomaly (MBA) gravity calculations. The focus of this investigation is a comparison of the Easter and Juan Fernandez microplates, which are located in the eastern Pacific Ocean along the Pacific, Nazca, and Antarctic plate boundaries. The microplates have several similar characteristics, including general size, time of formation, and clockwise rotation within the larger bounding mid-ocean ridge systems. Unlike the Juan Fernandez microplate, however, the Easter microplate is located near a mantle plume (Easter/Salas y Gomez). Previously published geochemical data suggest that material from this plume …

An Analysis Of Volcanic Lightning And Its Controlling Factors, Nathan Stamford

Honors Theses

Volcanic lightning, first documented during the 79 AD eruption of Mount Vesuvius, includes any electrical discharge that is generated during a volcanic eruption rather than a thunderstorm. By analyzing individual eruptions and performing laboratory experiments, previous research has identified multiple controlling factors that influence the charging mechanisms and generation of volcanic lightning. While the previous research has made significant discoveries about the phenomenon, the exact relationship between many of these controlling factors and volcanic lightning generation has been poorly quantified. In this study, we investigate these controlling factors and show that they have a wide range of influence over volcanic …

Geochemistry Of The Inyo Volcanic Chain, And Evaluation Of The Portable Niton Xrf Instrument, Dylan Terry

Electronic Theses, Projects, and Dissertations

The Inyo Volcanic Chain (IVC) is a series of rhyolitic lava domes straddling the northwest rim of the Long Valley Caldera (LVC), most recently erupting ~650 years ago, producing the South Deadman, Obsidian, and Glass Creek Domes. For this study, samples were analyzed for geochemistry and petrography at six of the IVC domes. To measure geochemistry, a portable x-ray fluorescence machine (PXRF) was used, in part to test how well it performed on felsic rocks. The PXRF performed poorly with the factory calibration in detecting most elements, though detection of some elements improved with a calibration curve applied. The three …

Textural Investigation Into Rapid Welding Transitions In The Tuff Of Leslie Gulch Along Succor Creek At The Mahogany Mountain-Three Fingers Rhyolite Field, Southeastern Oregon, Alicia J. Martinez-Garling, Martin J. Streck

Student Research Symposium

The Mahogany Mountain-Three Fingers Rhyolite Field (MM-TFrf) in southeastern Oregon, associated with mid-Miocene rhyolite activity and Columbia River flood basalts, has been the subject of geological scrutiny. Previous studies proposed separate origins for the tuff of Leslie Gulch (LGT) and Spring Creek, but Benson and Mahood (2006) suggested a single ignimbrite event at 15.8 Ma, prompting a reassessment of MM-TFrf's history. This research focuses on LGT, investigating textural disparities between welded and non-welded tuff formations. Petrographic examinations delve into the transformation stages of pyroclastic tuff deposition, revealing the dynamic influences of volcanological and magmatic processes on welded and non-welded tuff …

Petrologic And Geochemical Constraints On The Pre-Eruptive Storage Conditions Of Magmas Erupted During The ~12.5 Ka Flare Up Of Medicine Lake Volcano, Ca, Regina M. Khoury

Cal Poly Humboldt theses and projects

The Medicine Lake Volcano (MLV) system in the California Cascades is composed of a large shield volcano with numerous basaltic to rhyolitic vents on and around the flanks, many of which are aligned with N-S trending normal faults. A significant portion of the post-glacial volcanic activity at MLV is comprised of the ~12.5 ka “flare up” eruptions of basalt and basaltic andesite magmas from seven discrete flank vents. Prior work documented surface areas (0.02-198 km²), volumes (0.0001-4.35 km³), and eruption styles (Hawaiian to Strombolian; Donnelly-Nolan, 2010) of the ~12.5 ka deposits. This study uses new geologic …

Rift-Induced Disruption Of Cratonic Keels Drives Kimberlite Volcanism, Thomas M. Gernon, Stephen M. Jones, Sascha Brune, Thea K. Hincks, Martin Palmer, John C. Schumacher, Rebecca M. Primiceri, Matthew Field, William L. Griffin, Suzanne Y. O'Reilly, Derek Keir, Christopher J. Spencer, Andrew S. Merdith, Anne Glerum

Geology Faculty Publications and Presentations

Kimberlites are volatile-rich, occasionally diamond-bearing magmas that have erupted explosively at Earth’s surface in the geologic past^1,2,3. These enigmatic magmas, originating from depths exceeding 150 km in Earth’s mantle¹, occur in stable cratons and in pulses broadly synchronous with supercontinent cyclicity⁴. Whether their mobilization is driven by mantle plumes⁵ or by mechanical weakening of cratonic lithosphere^4,6 remains unclear. Here we show that most kimberlites spanning the past billion years erupted about 30 million years (Myr) after continental breakup, suggesting an association with rifting processes. Our dynamical …

Uas-Based Tracking Of The Santiaguito Lava Dome, Guatemala, Edgar U. Zorn, Thomas R. Walter, Jeffrey B. Johnson, René Mania

Geosciences Faculty Publications and Presentations

Imaging growing lava domes has remained a great challenge in volcanology due to their inaccessibility and the severe hazard of collapse or explosion. Changes in surface movement, temperature, or lava viscosity are considered crucial data for hazard assessments at active lava domes and thus valuable study targets. Here, we present results from a series of repeated survey flights with both optical and thermal cameras at the Caliente lava dome, part of the Santiaguito complex at Santa Maria volcano, Guatemala, using an Unoccupied Aircraft System (UAS) to create topography data and orthophotos of the lava dome. This enabled us to track …

Pumice Compositions And Mineral Chemistry From Lascar Volcano, Chile, Madelaine M. Stearn

Graduate Theses/Dissertations

Lascar volcano is one the most active volcano in the Central Volcanic Zone of the Andean Cordillera, with 36 Holocene eruptions including a VEI 4 eruption in April 1993. Activity has not been consistent throughout time, and therefore, the processes behind it are poorly understood. Lascar volcano has cyclic behavior and has had four stages of activity, each of which had a unique eruptive style and product composition. Stage I (<43 >ka) had primarily mafic andesite lavas erupted effusively from a stratocone. Stage II initiated with dome building events ESE of the original vent and culminated in the 26.45 ka …

Geochemical Analysis Of The Chinchín Formation In Southern Ecuador, Katherine Ludwig

Celebration of Learning

The subduction of the Nazca Plate under the South American Plate has led to the uplift of the majority of the Andes Mountains, but in Ecuador, the Nazca Plate subducts underneath the North Andes Plate, which then collides with the South American Plate. This tectonic setting has formed two parallel mountain chains as well as a complex series of basins between them. However, the formations that make up these basins are poorly understood. This study focuses on the Chinchín Formation, an ~3.5 km thick, volcanic formation that serves as the bedrock of the Quingeo Basin in southern Ecuador. This study …

Evolution Of A Flood Basalt Crustal Magmatic System: In Situ Mineral Data And Computational Modeling Of The Steens Basalt, Megan Graubard

All Master's Theses

Flood basalts are gigantic basaltic eruptions that modify the mass of the crust via intrusion of mantle-derived magma, and change its composition through interaction between magma and crust. The Steens Basalt, located in southeast Oregon, erupted approximately 16.8 million years ago, and is the oldest member of the Columbia River Basalt Group, the youngest and best-exposed flood basalt province on Earth. The Steens Basalt has an eruption volume of approximately 31,800 km³ and the duration of eruption is estimated to be between ~50,000 and 300,000 years. Major- and trace element whole rock data from 111 stratigraphically controlled samples from …

Geochemical And Petrological Characterization Of The Back Forty Volcanogenic Massive Sulfide Deposit, Anthony Robert Boxleiter

Masters Theses

The Back Forty Zn-Au deposit is the eastern-most Volcanogenic Massive Sulfide (VMS) deposit in the Penokean Volcanic Belt (PVB). It is the only VMS deposit found in Michigan, and is located along the east side of the Menominee River in Menominee County (45°26'57.5"N, 87°49'43.2"W). The Back Forty is the most zinc-enriched, copper depleted deposit among the major VMS deposits within the PVB that include Flambeau, Crandon, Bend, and Lynne. This work constitutes the first sulfur isotope study on the Back Forty VMS deposit.

The Back Forty is characterized by massive, semi-massive, disseminated and stringer sulfide mineralization hosted within felsic-dominated volcanic …

Interpretation Of Late Cretaceous Volcanic Mounds And Surrounding Gulfian Series Formations Using 3d Seismic Data In Zavala County, Texas, Laura Claire Bennett

Graduate Theses and Dissertations

The Late Cretaceous Gulfian series is a prominent and important series across the State of Texas that has been extensively studied since the nineteenth century. It is composed of series of southeast-dipping shelf carbonates and clastics deposited on the northwest margin of the Gulf of Mexico Basin. In south Texas, the Gulfian series was deposited in the Rio Grande Embayment and Maverick Basin and is comprised of the Eagle Ford Group, Austin Group, Anacacho Limestone, San Miguel Formation, Olmos Formation, and Escondido Formation that crop out and continue basinward in the subsurface. Late Cretaceous volcanism formed volcanic mounds composed of …

The Geology Of The Tuff Of Bridge Spring: Southern Nevada And Northwestern Arizona, Shirley Ann Morikawa

UNLV Theses, Dissertations, Professional Papers, and Capstones

The Tuff of Bridge Spring (TBS) is a regionally-widespread, andesite to rhyolite (59.50 to 74.91 wt. %) ash-flow tuff of mid-Miocene age (ca. 15.2 Ma) that is exposed in the northern Colorado River extensional corridor of southern Nevada and northwestern Arizona. Determination of the areal distribution, geochronology, lithology, geochemistry, and internal stratigraphy of the TBS is important for its establishment as a reliable stratigraphic reference horizon for tectonic reconstructions of the extensional corridor during the middle Miocene. Based on reoccurring patterns of major and trace element variation, the TBS is divided into constant Cr/variable SiO₂ and variable Cr/variable SiO …