Volcanology Commons^™

Mafic Volcanism In The Colorado Plateau: Basin And Range Transition Zone, Hurricane, Utah, Alexander Sanchez

UNLV Theses, Dissertations, Professional Papers, and Capstones

The Hurricane volcanic field (HVF) is a small-volume (0.48 km³) mafic volcanic field in the Colorado Plateau/Basin & Range Transition Zone located in the eastern part of the St. George basin in southwestern Utah. Strombolian-Hawaiian style eruptions produced thin (10 m) a'a lava flows and cinder (scoria) cones composed of vesicular basalt, bombs and agglutinate. Radiometric dating and geologic relationships demonstrate that the HVF formed over a period of at least 100,000 years. In the upper crust, magma probably rose along joints in sedimentary rocks because chains of volcanic vents follow joint orientation maxima in sedimentary rocks.

Three …

Geochemical Evolution Of A Mid-Miocene Synextensional Volcanic Complex: The Dolan Springs Volcanic Field, Northwestern Arizona, Scott Michael Mcdaniel

UNLV Theses, Dissertations, Professional Papers, and Capstones

The Dolan Springs volcanic field (DSV), of northwestern Arizona, is dominated by andesite and basaltic-andesite flows and breccias, with minor amounts of basalt, rhyolite, and ash-flow tuff. Geochemistry is used here as a tool to evaluate the roles and contributions of the lithospheric and asthenospheric mantles to magmatism related to Miocene extension in the Colorado River extension corridor (CREC). The majority of synextensional volcanic rocks in the DSV are geochemically similar to regional trends, but rare tholeiitic basalts erupted near the end of extension. The tholeiites have trace element signatures similar to ocean island basalt (OIB), but have isotopic values …

Geology And Geochemistry Of Tertiary Volcanic Rocks In The Northern Reveille And Southern Pancake Ranges, Nye County, Nevada, Kelly Brian Rash

UNLV Theses, Dissertations, Professional Papers, and Capstones

The northern Reveille and southern Pancake Ranges, located in the south-central Great Basin, experienced a prolonged history of Tertiary volcanism. Volcanic activity in this area began with the eruption of large-volumes of ash-flow tuffs from calderas of the central Nevada caldera complex. The Reveille Range and the southernmost portion of the Pancake Range are the site of two calderas that are the sources for the tuff of Goblin Knobs and tuff of northern Reveille Range. The tuff of Goblin Knobs (70.4-75.3 wt.% SiO₂) erupted from the caldera of Goblin Knobs (25.6 Ma) and is the thickest (~1700 m) …

The Holocene Sedimentary Framework Of The Lower Columbia River Basin, Edward Breed Gates

Dissertations and Theses

The Columbia River is the largest fluvially dominated estuary in the Pacific Northwest, yet the Holocene transgressive fill of this system has not previously been studied. Nearly 1500 industry borehole and water well records in the lower Columbia River basin (LCRB) were analyzed. These records document the sedimentary infilling of the lower 120 miles of the drowned river valley that occurred during the Holocene marine transgression (10-0 ka). Of particular importance is a key stratigraphic marker horizon of volcanic tephra that has been identified throughout the LCRB. INAA was used to determine the geochemical composition of the target tephra layer. …

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 …

Mapping The Distribution Of Vesicular Textures On Silicic Lavas Using The Thermal Infrared Multispectral Scanner, Jaime Ondrusek, Philip R. Christensen, Jonathan Fink

Geology Faculty Publications and Presentations

The Thermal Infrared Multispectral Scanner (TlMS) is a potentially powerful tool for mapping detailed chemical variations in silicic lava flows which in turn could expand knowledge of pre-eruption compositional gradients and mixing processes in silicic magma bodies. However, thermal infrared image data may be greatly influenced by the range of vesicular textures which occur on silicic flows . To investigate the effect of vesicularity on TIMS imagery independent of chemical variations, we studied Little Glass Mountain at the Medicine Lake Volcano of northern California, a large rhyolitic flow of uniform composition but textural heterogeneity. The imagery was recalibrated so that …

Three-Dimensional Transport Simulations Of The Dispersal Of Volcanic Aerosol From Mount Pinatubo, T. Duncan A. Fairlie

Mechanical & Aerospace Engineering Theses & Dissertations

A global finite-difference model that simulates the large-scale dynamics of the Earth's stratosphere and mesosphere is combined with a global spectral transport model to investigate aspects of the initial dispersal of the volcanic aerosol plume from the Mount Pinatubo eruption in 1991. Results of the modelling study are found to compare well with observations of the volcanic plume made from satellite instruments. Dynamical quantities, diagnosed from the simulated fields are used to provide insight into the evolution of the volcanic plume. Lagrangian trajectory analysis is used to help assess the performance of the Eulerian transport model and to highlight small-scale …

Shapes Of Venusian "Pancake" Domes Imply Episodic Emplacement And Silicic Composition, Jonathan H. Fink, Nathan T. Bridges, Robert E. Grimm

Geology Faculty Publications and Presentations

The main evidence available for constraining the composition of the large circular "pancake" domes on Venus is their gross morphology. Laboratory simulations using polyethylene glycol show that the height to diameter (aspect) ratios of domes given total volume depend critically on whether their extrusion was continuous or episodic, with more episodes leading to greater cooling and taller domes. Thus without observations of their emplacement, the compositions of venusian domes cannot be uniquely constrained by their morphology. However, by considering a population of 51 venusian domes to sent a sampling of many stages during the growth of domes with comparable histories, …

The Morphology Of Lava Flows In Planetary Environments: Predictions From Analog Experiments, Ross W. Griffiths, Jonathan H. Fink

Geology Faculty Publications and Presentations

The rates of surface cooling and lateral spreading are evaluated for lava flows on the surface of Earth, Venus, Mars, the Moon, and 10. Differences between the flow morphologies expected in these environments are then predicted under the assumption that the results of recent laboratory simulations oflavas using wax extruded beneath cold water (Fink and Griffiths, 1990) can be carried over. These experiments involved the spreading of viscous liquid under gravity in the presence of a solidifying surface crust and revealed a set of four distinct surface morphologies. Transitions from one morphology to the next occurred in a well-defined sequence …

Solidification And Morphology Of Submarine Lavas: A Dependence On Extrusion Rate, Ross W. Griffiths, Jonathan H. Fink

Geology Faculty Publications and Presentations

The results of recent laboratory experiments with wax extruded beneath relatively cold water may be extrapolated to predict the surface morphology of submarine lavas as a function of the extrusion rate and melt vIscosity. The experiments with solidifying wax indicated that the surface morphology was controlled by a single parameter, the ratio of the time taken for the surface to solidify, and a time scale for lateral flow. For submarine basalts a solution of the cooling problem (which is dominated by conduction in the lava but convective heat transfer in the water) and estimates of lava viscosities place this parameter …

Textural Constraints On Effusive Silicic Volcanism: Beyond The Permeable Foam Model, Jonathan H. Fink, Steven W. Anderson, Curtis R. Manley

Geology Faculty Publications and Presentations

Transitions between explosive and effusive phases of silicic volcanic eruptions have been related either to stratification of volatiles in the source magma body or to the loss of volatiles through the permeable host rock of the conduit. One way to distinguish between these two models is to map and analyze the vesicular and glassy textures found in silicic lava flows. In this paper we present textural observations and isotopic evidence from active and Recent silicic lava flows which show thaI at least some vesiculation occurs during surface advance of extrusions, after magma has reached the earth's surface. This view is …

The Sloan Sag: A Mid-Miocene Volcanotectonic Depression, North-Central Mccullough Mountains, Southern Nevada, Hayden L. Bridwell

UNLV Theses, Dissertations, Professional Papers, and Capstones

In the Hidden Valley area of the north-central McCullough Mountains, southern Nevada, mid-Miocene andesite and dacite domes, flows and pyroclastic units (the Sloan volcanics) partially fill a sag in the underlying Hidden Valley volcanics. The 13.5 km diameter sag formed during and/or after the eruption of the Sloan volcanics. Sagging was accommodated by a combination of movement on the McCullough Wash fault system, and subsidence into evacuated chambers.

Major, trace and rare-earth element geochemistry suggests that the rocks of the Sloan volcanics belong to four groups, each of which were produced by partial melting of chemically distinct sources. With the …

Scanning Electron Microscopic Study Of Quartz Sand Surface Features, Ash Hollow Formation, Ogallala Group, Western Nebraska, Patricia E. Helland, Robert F. Diffendal Jr.

School of Natural Resources: Faculty Publications

In field studies of the late Tertiary Ash Hollow Formation of the Ogallala Group in western Nebraska the alluvial deposits are composed of large volumes of sand and gravel up to large cobbles. Because the current understanding of the climate of the region at the time of deposition does not provide for a source for deposits of this character, a scanning electron microscopic study of the surface features on the quartz sand grains from these sediments was undertaken. Nine samples, collected from locations in Banner, Morrill and Keith Counties, were examined to see if they had one or more of …

Geology, Volcanology, And Petrology Of Cerro Bravo, A Young, Dactic, Stratovolcano In West-Central Colombia, David Tondl Lescinsky

LSU Historical Dissertations and Theses

The northernmost active Andean volcano, Cerro Bravo is a small, young, and very explosive stratovolcano. Cerro Bravo has produced voluminous tephra deposits, that are found> 30 km away, as well as, pumice flow deposits, block and ash flow deposits, and high-aspect lava flows, which are found proximally to the volcano. There have been eight episodes of activity during the past 6250±110 years (Herd, 1982), with the most recent <200 years ago and the present being a period of quiescence with no visible activity or thermal manifestations. Stratigraphic relationships suggest the occurrence of an initial explosive phase and a concluding effusive phase of activity during individual episodes. The products of volcanic activity at Cerro Bravo are a chemically and mineralogically monotonous suite of medium-K dacite and high-silica andesite (59.2- 67.5% SiO₂ pumices and lavas. The dominant phenocrysts present are plagioclase and hornblende (oxyhomblende in lavas) with lesser quantities of orthopyroxene, titanomagnetite, and rare augite and biotite also present. Petrology and eruption dynamics …

Taylor Instability In Ryholite Lava Flows, B. A. Baum, W. B. Krantz, Jonathan H. Fink, R. E. Dickinson

Geology Faculty Publications and Presentations

A refined Taylor instability model is developed to describe the surface morphology of rhyolite lava flows. The effect of the downslope flow of the lava on the structures resulting from the Taylor instability mechanism is considered. Squire's (1933) transformation is developed for this flow in order to extend the results to three-dimensional modes. This permits assessing why ridges thought to arise from the Taylor instability mechanism are preferentially oriented transverse to the direction of lava flow. Measured diapir and ridge spacings for the Little and Big Glass Mountain rhyolite flows in northern California are used in conjunction with the model …

The Mechanism Of Intrusion Of The Inyo Dike, Long Valley Caldera, California, Ze'ev Reches, Jonathan H. Fink

Geology Faculty Publications and Presentations

We analyze the intrusion of the 11-km-long lnyo Dike at the margins of Long Valley caldera, eastern California. The dike trends N07°W and is divided into at least three segments which are rotated by as much as 25° with respect to the main trend. The dike seems affected primarily by the regional stress field of right-lateral shear of the western United States and by the local thermal conditions of the crust; the dike seems unaffected by the preexisting caldera margins and Sierra-Nevada frontal fault system. The high heat flow in Long Valley caldera implies that crustal rocks below 3-4.5 km …

Explosion Structures In Grande Ronde Basalt Of The Columbia River Basalt Group, Near Troy, Oregon, Leonard Lee Orzol

Dissertations and Theses

Explosion structures occur in flows of Grande Ronde Basalt in the study area near Troy, Oregon. Data from nineteen stratigraphic sites indicate that the maximum number of flows that contain explosion structures at any one site is six. In the informally named Troy flow, explosion structures are widespread.

Each flow that contains explosion structures can be divided into two cooling units. The first cooling units occupy troughs in the pre-eruption topography and are up to 10 meters thick. The second cooling units contain the explosion structures and are up to 100 meters thick. The thickness of flows that contain explosion …

Petrology Of The Kula Volcanic Field, Western Turkey, Julie M. Dyer

Geology Theses and Dissertations

The Kula volcanics are a small Pleistocene to Recent volcanic field located on the north shoulder of the Gediz graben, approximately 120 km east of Izmir. The field consists of a mixture of flows, small cones and pyroclastic deposits erupted during three periods of volcanic activity beginning about one million years ago. The volcanics range in composition from basanites to trachybasalts, commonly porphyritic with abundant clinopyroxene, olivine and amphibole phenocrysts. The lavas also host a wide variety of megacrysts, crustal xenoliths and hydrous mantle-derived nodules. These volcanics unconformably overlie Neogene lacustrine sedimentary rocks and the metamorphic basement rocks of the …

Identification Of Endmembers For Magma Mixing In Little Sitkin Volcano, Alaska, Douglas A. Wolf

Geology Theses and Dissertations

Little Sitkin island is an Aleutian calc-alkalic volcanic center that has erupted a suite of lavas ranging from andesite through rhyodacite. Whole-rock chemistry of these lavas indicates contrasting evolutionary processes; major-oxide silica variation diagrams exhibit linear trends that are suggestive of magma-mixing while trace-element trends are largely controlled by accessory-phase fractionation.
Plagioclase, the dominant phenocryst phase in all lavas, commonly occurs in two distinct populations with markedly different compositions and textures. Both normal and reverse zonation is noted in the plagioclase and clinopyroxene of several samples. In addition, clinopyroxene is found as rims on orthopyroxene grains and as cores with …

Fracture Detection In A Volcanic Oil Reservoir Using Discriminant Analysis Of Well Log Data, Joseph William Cross

OES Theses and Dissertations

A new method of detecting fractures using well logs is presented. The technique uses discriminant analysis to distinguish fractured from unfractured reservoir rock and was developed for the volcanic pay zone of Jatibarang oilfield, West Java, Indonesia.

The a priori information required to derive the discriminant function was provided by 22 wells known to penetrate intervals of either fractured or unfractured volcanics. The samples consisted of these 22 intervals digitized in one-meter increments (1256 meters total thickness). The discriminating variables were the petrophysical measurements made by 10 different types of well logs.

Discriminant analysis correctly classified 94.2% of the total …

Tephrostratigraphy Of The Middle Eocene Chumstick Formation, Cascade Range, Douglas County, Washington, Matthew John Mcclincy

Dissertations and Theses

This study outlines the ash (tuff) bed stratigraphy (tephrostratigraphy) in the middle Eocene Chumstick Formation of central Washington. The tuff beds provide local marker beds enabling interpretation of the stratigraphy and structure of the formation. The chemical signature of these units provides the basis on which the units can be traced over broad areas in the basin of deposition. Correlations of tuff beds were obtained over distances of 41 km.

The tephrostratigraphy of the Chumstick Formation consists of nineteen tuff marker beds. Seventeen of these units are chemically characterized in this study. Ten elements were used to fingerprint these tuff …

Tiltmeter Analysis Of Mount St. Helens, Skamania County, Washington, Edward Charles Brown

Dissertations and Theses

Mount St. Helens returned to an active eruptive state March 20, 1980. Since then explosive and dome building eruptions have caused major topographic changes to the mountain and surrounding drainages. Monitoring of the southern side of the mountain by six tiltmeters at distances between 6 km and 12 km was conducted during the period of July 1, 1980 to December 31, 1980. Records obtained from the tiltmeters were analyzed and compared to data from precision geodetic surveys.

Igneous Dikes At Long Valley, Ca: Emplacement Mechanisms And Associated Geologic Structures, David D. Pollard, Jonathan H. Fink, Paul T. Delaney

Geology Faculty Publications and Presentations

Two hypotheses for dike emplacement are: (1) magma flows into and dilates pre-existing fractures; or (2) magma flows into and dilates self-generated fractures. In the first case dikes should be parallel to an element of the rock fabric; in the second, they should be perpendicular to the least compressive stress. The two hypotheses suggest different dike intrusion and fissure eruption mechanisms and therefore different strategies for monitoring igneous events at Long Valley. We derive a method to distinguish the two mechanisms, a priori, from in-situ stress measurements and estimates of magma pressure. Estimates of relative dilation and slip across a …

Quaternary Volcanology Of The West Crater-Soda Peaks Area, Southern Washington Cascade Range, David R. Polivka

Dissertations and Theses

The West Crater-Soda Peaks area covering about 100 km is located 35 km southeast of Mount St. Helens in southern Washington State. It is one of several Quaternary monogenetic High Cascade volcanic centers overlying the Ohaaapecosh Formation of the Western Cascade Group and interstratified glacial till.These volcanic centers are the most westerly of the range.

Geology And Hydrothermal Alteration, Glass Buttes, Southeast Oregon, Dulcy Annette Berri

Dissertations and Theses

The Glass Buttes volcanic complex consists of many domes and individual vents that erupted both rhyolitic and basaltic lavas during the late Miocene to early Pliocene. The east half of the complex, in the vicinity of Little Glass Butte, contains interfingering, finely flow-banded rhyolite and black obsidian flows. The youngest unit, an obsidian, has been dated at 4.9 m.y. East of Little Glass Butte lie two northwest-trending ridges, Antelope and Cascade Ridges, composed of two or more overlapping exogenous domes that formed along northwest-trending faults.

Geology Of A Volcanic Complex On The South Flank Of Mount Jefferson, Oregon, Brian Lee Gannon

Dissertations and Theses

The volcanic stratigraphy and petrography is described for a 46 km² area on the southern flank of Mount Jefferson in the north-central part of the Oregon High Cascades. Here, volcanic processes have been active throughout Quaternary time, resulting in complex stratigraphic relationships. In addition, three formerly recognized glaciations and a two-phase period of neoglaciation have eroded the terrain, depositing tills in contact or interstratified with the volcanic units. Collectively, these processes and the resulting deposits are characteristic of High Cascades development.

Rheological Properties Of Mudflows Associated With The May 1980 Eruptions Of Mount St. Helens Volcano, Washington, Jonathan H. Fink, Michael C. Malin, Richard E. D'Alli, Ronald Greeley

Geology Faculty Publications and Presentations

Rheological properties of three recent mudflows at Mount St. Helens were estimated using techniques developed for determining the properties of debris flows based on the geometry of their deposits. Calculated yield strengths of 1100, 1000, and 400 Pa, maximum flow velocities of 10 to 31 m/s, volumetric flow rates of 300 to 3400 m³/s, and plastic viscosities of 20 to 320 Pa-s all compare favorably with measured and estimated values cited in the literature. A method for determining likely sites of future mudflow initiation based on these data is outlined.

Emission Rates Of Co2 From Plume Measurements., D. M. Harris, M. Sato, T. J. Casadevall, William I. Rose, T. J. Bornhorst

Michigan Tech Publications, Part 1

Most of the CO2 that emanated from Mount St. Helens became part of the gas plume as it moved away from the volcano. An airborne technique was developed for continuous sampling and infrared analysis for CO2 in the plume. The CO2-emission rates were determined by measuring the area, the horizontal velocity, and the CO2 concentration anomaly in vertical cross sections of the plume The emission rate varied from 2100 t/day to about 22 000 t/day.-from Author

Radar Observations Of Ash Eruptions, D. M. Harris, William I. Rose, R. Roe, M. R. Thompson

Michigan Tech Publications, Part 1

Radar systems located at Portland, Oreg., Seattle, Wash., and near Spokane, Wash., have been used extensively for observations of ash clouds from explosive volcanic eruptions at Mount St. Helens during 1980. Eruption clouds are composed of silicate particles and are therefore detectable by radar. Radar observations can be made at night and in overcast weather when conventional observations of eruptions are difficult.-from Authors

Chemical Trends In The Ice Springs Basalt, Black Rock Desert, Utah, W. C. Lynch, W. P. Nash

All U.S. Government Documents (Utah Regional Depository)

The Holocene Ice Springs volcanic field of west-central Utah consists of 0.53 km3 of tholeitic basalts erupted as a sequence of nested cinder cones and associated lava flows. Whole rock x-ray fluorescence and atomic absorption analysis of ninety-six samples of known relative age document statistically significant inter- and intra- eruption chemical variations. Elemental trends include increases in Ti, Fe, Ca, P, and Sr and decreases in Si, K, Rb, Ni, Cr, and Zr with decreasing age. Microprobe analyses of microphenocrysts of olivine, plagioclase, and Fe-Ti oxides and of groundmass olivine, plagioclase, and clinopyroxene indicate limited chemical variation between mineral assemblages …