DOCSLIB.ORG

Methods Used in Studying Modern Pyroclastic Deposits

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Methods Used in Studying Modern Pyroclastic Deposits APPENDIX I Methods used in studying modern pyroclastic deposits 1.1 Physical analysis The methods used to measure these, and the major uses of these measurements are set out below. Geologists who work solely on ancient volcanic rocks often have only a limited conception of the techniques 1.1.1 THICKNESS employed to study Recent unconsolidated pyroclastic deposits, and so may not fully understand how the data Maximum thickness of a pyroclastic fall deposit is are obtained or expressed. Many of the problems measured in centimetres or metres, and the measurements encountered in the study of modern pyroclastic deposits are used to construct an isopach map. In the figures are similar to those found in sedimentary rocks, where accompanying Chapter 6 there are a number of examples grainsize, grain shape, geometry of the deposit and of such maps, which in many cases, are a meaningful internal fabric must be the tools used to determine the indication of: physical processes controlling their formation and de­ (a) the vent position, position. The pioneers in this type of approach were (b) the dispersal, which can be related to the type of undoubtedly Japanese volcanologists (e.g. Kuno 1941, eruption, and Aramaki 1956, Katsui 1959, Murai 1961, Kuno et al. (c) the volume of the deposit. 1964), whereas G. P. L. Walker (e.g. 1971, 1973b) can be credited with extending and developing the approach. The following are properties that are now routinely Construction of an isopach map entails mapping out measured in the physical analysis of modern pyroclastic the deposit, sometimes over large areas. However, by deposits: mapping we do not mean tracing lithological boundaries between deposits, as these are usually so complex that no thickness attempt is made to draw them. Thus, a map of a Recent maximum grain size pyroclastic fall deposit generally shows its inferred grainsize distribution original distribution, and not its present outcrop pattern, proportions of components as between datum points the deposit could be partially or crystal content of pumice clasts completely eroded. Indeed, non-welded pyroclastic density and porosity deposits may be ephemeral (Ch. 10). In addition, outcrops may be so rapidly overgrown and badly 469 470 APPENDIX I: STUDYING MODERN DEPOSITS weathered that they cannot be used. For example, new 1.l.2 MAXIMUMGRAINSIZE roadcuts in the tropical Caribbean are sometimes completely overgrown within four or five years. Because Measuring the average maximum juvenile and lithic clast pyroclastic fall deposits can change markedly laterally, it size is an important field technique, which involves is preferable to use reasonably closely spaced datum measuring, at numerous localities, the long axis of several points. Although spacing ultimately depends on the type of the largest clasts in a deposit. In some detailed sections of eruption, for the large plinian fall deposits localities the variation in grainsize between different layers of one within 1 km of each other are favoured. Within these deposit is measured. Usually the sizes of the three or five distances correlation is more certain, and internal largest clasts are then averaged, and this would closely changes can be carefully documented. This is very approximate the coarsest one-percentile often quoted by important in correlating deposits between localities and sedimentologists. Average maximum pumice (or scoria) in understanding the eruption and its stratigraphy. and lithic sizes can be plotted up as isopleth maps (Chs The volumes of air-fall deposits have been calculated 6-8). As with isopach maps, maximum-size isopleth from isopach maps in various ways. A common method maps are important in locating the vent from which involves measuring the area enclosed by each isopach and pyroclastic fall deposits were erupted, and for comparing then to plot area against thickness on a log-log 'area plot' their dispersal in order to characterise the type of (Fig. 6.18). A curve, or two straight lines (Rose et al. eruption. However, for pyroclastic fall deposits, such 1973), are fitted to the data, and integration of this curve isopleth maps have certain advantages over an isopach gives the volume. Other methods include plots of volume map, because at some localities it may not be the original against thickness and plots based on theoretical isopach depositional thickness that is being measured. The top of shape (Froggatt 1982). All of these methods involve a deposit may have been eroded by either a later surge or extrapolation of isopachs to the low-thickness distal limits flow, which is sometimes common with near-vent plinian of the deposit where outcrop may be poorly eroded. This deposits, or by later local erosion or soil-forming introduces major uncertainty for larger, more widely processes. It may also have been overthickened by dispersed types of deposits, especially where secondary secondary slumping, especially if the fall was deposited thickening might have been important (Ch. 6). To try to on a steep slope. Also, some extremely widely dispersed resolve this, G. P. L. Walker (1980, 1981b, c) developed (ultraplinian) deposits may be thickest just down-wind of an independent method for estimating the total volume of the vent (Chs 6 & 8), and secondary thickening of distal plinian deposits, based on crystal concentration studies ash may occur (Ch. 6). (see below) of the Taupo ultraplinian, and Waimihia and Measurements of maximum clast size are also used to Hatepe plinian deposits. Once the total volume erupted analyse the energetics of pyroclastic fall eruptions. This is had been estimated from the proportion of free crystals especially so for large ballistic clasts; that is, those clasts relative to the magmatic ratio as represented in pumice which are so heavy that they follow ballistic trajectories clasts, a straight-line extrapolation could be made at the and are unaffected by wind drift. The distance at which low thickness end on an area plot to a selected limiting ballistics fall from the vent (that is, their range) can be thickness value, so giving the same volume as would be used to estimate initial gas thrust velocities from the vent, calculated by integration of the area curve. It was found or the muzzle velocities of the ballistics from the vent that for all three deposits extrapolations to the same lower (Ch. 6). L. Wilson (1972) presented tables of calculated limiting thickness of 1 Ilm had nearly identical slopes. ranges for particles of varying radii and density, launched Total erupted volumes of other plinian deposits can be at speeds between 10 and 1000 m S-l and various conveniently estimated on an area plot by extrapolation angular elevations. These are reproduced in Table 1.1, parallel to this slope, using the same limiting thickness of and cover most ballistic clast sizes (Ch. 6). 1 Ilm (G. P. L. Walker 1981b; Table 6.2). For plinian deposits the muzzle velocity can be Measurements of the variation in the thickness of conveniently calculated from measurements of maximum pyroclastic flow and surge deposits are less meaningful in clast size using the equation of L. Wilson (1976, 1978): terms of an indicator of vent location. This is because (8grooo) both are gravity-controlled mass flows, which therefore uij= (Ll) tend to pond in depressions. However, thickness is 3CQo important in calculation of the volumes of such deposits. where Uo is the velocity of the gas (or muzzle velocity), C is the drag coefficient (-1 for plinian velocities), Qo is the PHYSICAL ANALYSIS 471 Table 1.1 Logarithms (base 10) of the ranges of larger pyroclastic particles (after L. Wilson 1972). Velocity Density Launched at 45° radius Launched at 66° radius Launched at 37° radius (m S~l) (g cm-3) (cm) (cm) (cm) 1.0 3.0 10.0 30.0 100.0 1.0 3.0 10.0 30.0 100.0 1.0 3.0 10.0 30.0 100.0 3.5 2.9556 3.0032 30075 2.8261 2.8736 2.8786 1.9790 20211 2.0268 2.5 2.9369 3.0017 3.0070 2.8073 2.8719 2.8785 1.9614 2.0207 2.0267 10 1.0 2.8559 2.9914 30060 2.7242 2.8601 2.8770 1.8830 2.0099 2.0254 0.5 2.7579 2.9760 30043 2.6222 2.8427 2.8753 1.7846 1.9937 2.0236 3.5 3.6440 3.9315 3.9583 3.4896 3.8010 3.8290 2.6641 2.9505 2.9775 2.5 3.5719 3.9208 3.9571 3.4235 3.7897 3.8276 2.5897 2.9395 2.9762 30 1.0 3.3383 3.8680 3.9483 3.1834 3.7329 3.8180 2.3497 2.8843 2.9673 0.5 3.1364 3.7965 3.9356 2.9752 3.6544 3.8036 2.1373 2.8070 2.9540 3.5 4.0418 4.6867 4.9660 3.8644 4.5529 4.8358 3.0228 3.7156 3.9873 2.5 3.7372 4.6173 4.9514 3.7468 4.4821 4.8195 2.9034 3.6437 3.9721 100 1.0 3.6042 4.3999 4.8817 3.4194 4.2548 4.7461 2.5717 3.4116 3.9026 0.5 3.3549 4.2139 4.7912 3.1673 4.0556 4.6504 2.4068 3.2078 3.8097 3.5 4.23894.7075 5.0257 5.3861 5.6581 4.04104.5111 4.86735.23575.5274 3.1877 3.6669 4.0293 4.3988 4.6906 2.5 4.11104.58494.9177 5.2957 5.5914 3.91114.38524.75735.13685.4571 3.05683.53943.91574.30004.6212 300 1.0 3.7592 4.2319 4.6183 5.0127 5.3732 3.5575 4.0304 4.4499 4.8381 5.2261 2.69973.17703.59934.00064.3900 0.5 3.4931 3.9647 4.3891 4.7744 5.1779 3.29063.75904.21034.59205.0199 2.43022.90153.35493.75214.1815 3.5 4.29594.77445.13235.54045.9162 4.0926 4.5719 4.9631 5.3820 5.7887 3.2356 3.7238 4.1204 4.5432 4.9575 2.5 4.1652 4.6458 5.0139 5.4302 5.8157 3.9602 4.4406 4.8427 5.2624 5.6795 3.10243.59123.99644.42274.8464 600 1.0 3.8073 4.2817 4.6933 5.1087 5.5245 3.60134.07584.51554.92565.3690 2.74043.2191 3.66074.08364.5308 0.5 3.5373 4.0098 4.4526 4.8524 5.2928 3.3309 3.8005 4.2660 4.6621 5.1253 2.4679 2.9400 3.4069 3.8174 4.2831 3.5 4.34264.82755.21125.65106.1029 4.1354 4.6207 5.0348 5.4885 5.9963 3.27553.76934.18814.64825.1767 2.5 4.21004.6948 5.0861 5.5273 5.9760 4.0014 4.4857 4.9075 5.3542 5.8474 3.1407 3.6332 4.0573 4.5119 5.0191 1000 1.0 3.8477 4.32314.75175.18105.6329 3.63844.11394.56704.9921 5.4732 2.7752 3.2547 3.7089 4.1463 4.6333 0.5 3.5749 4.0479 4.5032 4.9130 5.3772 3.36543.83584.31084.71735.2033 2.5003 2.9732 3.4489 3.8687 4.3578 effective density of the volcanic gas in the vent I.1.3 GRAINSIZE DISTRIBUTION (0.25 kg m-3 for dusty gas), g is the acceleration due to gravity, ro is the radius of the average maximum clast at Mechanical or granulometric analyses are used as the vent and 00 is its density (generally taken as 2.5 g cm-3 main source of data when examining the grainsize for lithics).
Load more

Recommended publications
  • Volcanology and Mineral Deposits
    THESE TERMS GOVERN YOUR USE OF THIS DOCUMENT Your use of this Ontario Geological Survey document (the “Content”) is governed by the terms set out on this page (“Terms of Use”). By downloading this Content, you (the “User”) have accepted, and have agreed to be bound by, the Terms of Use. Content: This Content is offered by the Province of Ontario’s Ministry of Northern Development and Mines (MNDM) as a public service, on an “as-is” basis. Recommendations and statements of opinion expressed in the Content are those of the author or authors and are not to be construed as statement of government policy. You are solely responsible for your use of the Content. You should not rely on the Content for legal advice nor as authoritative in your particular circumstances. Users should verify the accuracy and applicability of any Content before acting on it. MNDM does not guarantee, or make any warranty express or implied, that the Content is current, accurate, complete or reliable. MNDM is not responsible for any damage however caused, which results, directly or indirectly, from your use of the Content. MNDM assumes no legal liability or responsibility for the Content whatsoever. Links to Other Web Sites: This Content may contain links, to Web sites that are not operated by MNDM. Linked Web sites may not be available in French. MNDM neither endorses nor assumes any responsibility for the safety, accuracy or availability of linked Web sites or the information contained on them. The linked Web sites, their operation and content are the responsibility of the person or entity for which they were created or maintained (the “Owner”).
    [Show full text]
  • Source to Surface Model of Monogenetic Volcanism: a Critical Review
    Downloaded from http://sp.lyellcollection.org/ by guest on September 28, 2021 Source to surface model of monogenetic volcanism: a critical review I. E. M. SMITH1 &K.NE´ METH2* 1School of Environment, University of Auckland, Auckland, New Zealand 2Volcanic Risk Solutions, Massey University, Palmerston North 4442, New Zealand *Correspondence: k.nemeth@massey.ac.nz Abstract: Small-scale volcanic systems are the most widespread type of volcanism on Earth and occur in all of the main tectonic settings. Most commonly, these systems erupt basaltic magmas within a wide compositional range from strongly silica undersaturated to saturated and oversatu- rated; less commonly, the spectrum includes more siliceous compositions. Small-scale volcanic systems are commonly monogenetic in the sense that they are represented at the Earth’s surface by fields of small volcanoes, each the product of a temporally restricted eruption of a composition- ally distinct batch of magma, and this is in contrast to polygenetic systems characterized by rela- tively large edifices built by multiple eruptions over longer periods of time involving magmas with diverse origins. Eruption styles of small-scale volcanoes range from pyroclastic to effusive, and are strongly controlled by the relative influence of the characteristics of the magmatic system and the surface environment. Gold Open Access: This article is published under the terms of the CC-BY 3.0 license. Small-scale basaltic magmatic systems characteris- hazards associated with eruptions, and this is tically occur at the Earth’s surface as fields of small particularly true where volcanic fields are in close monogenetic volcanoes. These volcanoes are the proximity to population centres.
    [Show full text]
  • Insight Into Subvolcanic Magma Plumbing Systems Wendy A
    Insight into subvolcanic magma plumbing systems Wendy A. Bohrson Department of Geological Sciences, Central Washington University, 400 E. University Way, Ellensburg, Washington 98926, USA The Island of Hawaii, which is among the of CO2 inclusions (Bohrson and Clague, 1988; best-studied volcanic islands on Earth, provides Roedder, 1965). Rare gabbro from layer 3 of the lush ground for debates in volcanology that oceanic crust has also been identifi ed (Clague, focus on how magmatic systems evolve in space 1987a). Thus, a likely location for the deeper and time. Hawaiian volcanoes evolve through chamber is at the base of the oceanic crust. The four eruptive stages that are characterized by relatively low magma supply associated with distinct composition, magma supply rate, and the pre-shield and rejuvenated stages appar- Shallow magma plumbing degree of mantle melting (e.g., Clague, 1987a, ently precludes any persistent crustal magma system 1987b, and references therein). The pre-shield plumbing system; spinel lherzolite and garnet (shield stage) stage, fi rst identifi ed on Loihi Seamount (Moore pyroxenite xenoliths originate in the mantle et al., 1982), erupts mostly alkalic basalt and based on geobarometry, compositional charac- Deep basanite that refl ect a small magma supply and teristics, and other constraints (e.g., Frey and magma plumbing derive from relatively small degrees of mantle Roden, 1987; Frey, 1982). system melting. During the shield stage, tholeiitic Although rare on Hawaiian volcanoes, the (shield and post-shield stage) basalt (like that currently erupted at Kilauea more evolved compositions also provide insight and Mauna Loa) dominates, and refl ects com- into plumbing system dynamics.
    [Show full text]
  • Anatomy of a Volcanic Eruption: Case Study: Mt. St. Helens
    Anatomy of a Volcanic Eruption: Case Study: Mt. St. Helens Materials Included in this Box: • Teacher Background Information • 3-D models of Mt. St. Helens (before and after eruption) • Examples of stratovolcano rock products: Tuff (pyroclastic flow), pumice, rhyolite/dacite, ash • Sandbox crater formation exercise • Laminated photos/diagrams Teacher Background There are several shapes and types of volcanoes around the world. Some volcanoes occur on the edges of tectonic plates, such as those along the ‘ring of fire’. But there are also volcanoes that occur in the middle of tectonic plates like the Yellowstone volcano and Kilauea volcano in Hawaii. When asked to draw a volcano most people will draw a steeply sided, conical mountain that has a depression (crater) at the top. This image of a 'typical' volcano is called a stratovolcano (a.k.a. composite volcano). While this is the often visualized image of a volcano, there are actually many different shapes volcanoes can be. A volcano's shape is mostly determined by the type of magma/lava that is created underneath it. Stratovolcanoes get their shape because of the thick, sticky (viscous) magma that forms at subduction zones. This magma/lava is layered between ash, pumice, and rock fragments. These layers of ash and magma will build into high elevation, steeply sided, conical shaped mountains and form a 'typical' volcano shape. Stratovolcanoes are also known for their explosive and destructive eruptions. Eruptions can cause clouds of gas, ash, dust, and rock fragments to eject into the atmosphere. These clouds of ash can become so dense and heavy that they quickly fall down the side of the volcanoes as a pyroclastic flow.
    [Show full text]
  • Ignimbrites to Batholiths Ignimbrites to Batholiths: Integrating Perspectives from Geological, Geophysical, and Geochronological Data
    Ignimbrites to batholiths Ignimbrites to batholiths: Integrating perspectives from geological, geophysical, and geochronological data Peter W. Lipman1,* and Olivier Bachmann2 1U.S. Geological Survey, Mail Stop 910, Menlo Park, California 94028, USA 2Institute of Geochemistry and Petrology, ETH Zurich, CH-8092 Zürich, Switzerland ABSTRACT related intrusions cooled and solidified soon shorter. Magma-supply estimates (from ages after zircon crystallization, as magma sup- and volcano-plutonic volumes) yield focused Multistage histories of incremental accu- ply waned. Some researchers interpret these intrusion-assembly rates sufficient to gener- mulation, fractionation, and solidification results as recording pluton assembly in small ate ignimbrite-scale volumes of eruptible during construction of large subvolcanic increments that crystallized rapidly, leading magma, based on published thermal models. magma bodies that remained sufficiently to temporal disconnects between ignimbrite Mid-Tertiary processes of batholith assembly liquid to erupt are recorded by Tertiary eruption and intrusion growth. Alternatively, associated with the SRMVF caused drastic ignimbrites, source calderas, and granitoid crystallization ages of the granitic rocks chemical and physical reconstruction of the intrusions associated with large gravity lows are here inferred to record late solidifica- entire lithosphere, probably accompanied by at the Southern Rocky Mountain volcanic tion, after protracted open-system evolution asthenospheric input. field (SRMVF). Geophysical
    [Show full text]
  • Pyroclastic Flow Hazards
    Pyroclastic Flow Hazards Lecture Objectives -definition and characteristics -generation of pyroclastic flows -impacts and hazards What are pyroclastic flows? Pyroclastic flows are high- density mixtures of hot, dry rock fragments and hot gases that move away from the vent that erupted them at high speeds. Generation Mechanisms: -explosive eruption of molten or solid rock fragments, or both. -non-explosive eruption of lava when parts of dome or a thick lava flow collapses down a steep slope. Most pyroclastic flows consist of two parts: a basal flow of coarse fragments that moves along the ground, and a turbulent cloud of ash that rises above the basal flow. Ash may fall from this cloud over a wide area downwind from the pyroclastic flow. Mt. St. Helens Effects of pyroclastic flows A pyroclastic flow will destroy nearly everything in its path. With rock fragments ranging in size from ash to boulders traveling across the ground at speeds typically greater than 80 km per hour, pyroclastic flows knock down, shatter, bury or carry away nearly all objects and structures in their way. The extreme temperatures of rocks and gas inside pyroclastic flows, generally between 200°C and 700°C, can cause combustible material to burn, especially petroleum products, wood, vegetation, and houses. Pyroclastic flows vary considerably in size and speed, but even relatively small flows that move <5 km from a volcano can destroy buildings, forests, and farmland. On the margins of pyroclastic flows, death and serious injury to people and animals may result from burns and inhalation of hot ash and gases. Pyroclastic flows generally follow valleys or other low-lying areas and, depending on the volume of rock debris carried by the flow, they can deposit layers of loose rock fragments to depths ranging from less than one meter to more than 200 m.
    [Show full text]
  • 31 a Preliminary Study Of
    31 A PRELIMINARY STUDY OF THE: TERTIARY VOLCANIC AND SEDIMENTARY ROCKS, GÜMELE, ESKİŞEHİR Eskişehir, Gümele Çevresindeki Tersiyer Volkanik ve Sedimanter Kayaçlarda Bir Ön Çalışma Taylan Lünel Middle East Technical University, Department of Geological Engineering Ankara ÖZ. — Seyitgazi-Eskişehir antiklinoriumu'nun çok fazla deforme olmuş ve metamorfizmaya uğramış kayaçlarının kuzey-kuzeybatısında bulunan sedimanter ve volkanik kayaçlar incelenmiştir. Karasal ve gölsel fasiyesde meydana gelen Tersi- yer sedimanter kayaçlar Güney Eskişehir küvetinde olunmuşlardır. Karasal fasiye- si meydana getiren kayaç birimlerini kaba kumtaşları, kumtaşları, bitki kalıntıları ihtiva eden kil ve marnlar ve serpantinit blokları taşıyan bazal konglomerası teşkil etmektedir. Gölsel fasiyes ise genellikle killi ve tüflü kalkerler, kalkerler, marnlar, kon- glomeralar ve tüflerden meydana gelmiştir. Küvetteki en eski sedimanlar ve piroklas- tikler Alt Miosen'de oluşmuşlardır. Yataya yakın konumlanmış bazik-intermediyar lav akıntıları Pliosen yaşlı olup Altüst Neojen sedimantasyon kesikliğinde meyda- na gelmiştir. Üst Neojen sedimanter kayaçları intermediyar-basaltik volkaniklerin üzerinde ince bandlar şeklinde bulunurlar. Bu birim marn ve kalkerlerden meyda- na gelmiştir. Alt Miosen’de asid volkanik faaliyetler neticesinde meydana gelen sil- lar (unweldd tuffs) oligomikt konglomeralardan evvel teşekkül etmiştir. Bu volkanik aktitivite muhtemelen kesikli ve kısıtlı olarak devam etmiş ve tüflü kalkerleri mey- dana getirmiştir. Pliosen yaşlı bazik-intermediyar
    [Show full text]
  • Hawaiian Volcanoes: from Source to Surface Site Waikolao, Hawaii 20 - 24 August 2012
    AGU Chapman Conference on Hawaiian Volcanoes: From Source to Surface Site Waikolao, Hawaii 20 - 24 August 2012 Conveners Michael Poland, USGS – Hawaiian Volcano Observatory, USA Paul Okubo, USGS – Hawaiian Volcano Observatory, USA Ken Hon, University of Hawai'i at Hilo, USA Program Committee Rebecca Carey, University of California, Berkeley, USA Simon Carn, Michigan Technological University, USA Valerie Cayol, Obs. de Physique du Globe de Clermont-Ferrand Helge Gonnermann, Rice University, USA Scott Rowland, SOEST, University of Hawai'i at M noa, USA Financial Support 2 AGU Chapman Conference on Hawaiian Volcanoes: From Source to Surface Site Meeting At A Glance Sunday, 19 August 2012 1600h – 1700h Welcome Reception 1700h – 1800h Introduction and Highlights of Kilauea’s Recent Eruption Activity Monday, 20 August 2012 0830h – 0900h Welcome and Logistics 0900h – 0945h Introduction – Hawaiian Volcano Observatory: Its First 100 Years of Advancing Volcanism 0945h – 1215h Magma Origin and Ascent I 1030h – 1045h Coffee Break 1215h – 1330h Lunch on Your Own 1330h – 1430h Magma Origin and Ascent II 1430h – 1445h Coffee Break 1445h – 1600h Magma Origin and Ascent Breakout Sessions I, II, III, IV, and V 1600h – 1645h Magma Origin and Ascent III 1645h – 1900h Poster Session Tuesday, 21 August 2012 0900h – 1215h Magma Storage and Island Evolution I 1215h – 1330h Lunch on Your Own 1330h – 1445h Magma Storage and Island Evolution II 1445h – 1600h Magma Storage and Island Evolution Breakout Sessions I, II, III, IV, and V 1600h – 1645h Magma Storage
    [Show full text]
  • Structure of the Yegua-Jackson Aquifer of the Texas Gulf Coastal Plain Report
    Structure of the Yegua-Jackson Aquifer of the Texas Gulf Coastal Plain Report ## by Legend Paul R. Knox, P.G. State Line Shelf Edge Yegua-Jackson outcrop Van A. Kelley, P.G. County Boundaries Well Locations Astrid Vreugdenhil Sediment Input Axis (Size Relative to Sed. Vol.) Facies Neil Deeds, P.E. Deltaic/Delta Front/Strandplain Wave-Dominated Delta Steven Seni, Ph.D., P.G. Delta Margin < 100' Fluvial Floodplain Slope 020406010 Miles Shelf-Edge Delta Shelf/Slope Sand > 100' Texas Water Development Board P.O. Box 13231, Capitol Station Austin, Texas 7871-3231 September 2007 TWDB Report ##: Structure of the Yegua-Jackson Aquifer of the Texas Gulf Coastal Plain Texas Water Development Board Report ## Structure of the Yegua-Jackson Aquifer of the Texas Gulf Coastal Plain by Van A. Kelley, P.G. Astrid Vreugdenhil Neil Deeds, P.E. INTERA Incorporated Paul R. Knox, P.G. Baer Engineering and Environmental Consulting, Incorporated Steven Seni, Ph.D., P.G. Consulting Geologist September 2007 This page is intentionally blank. ii This page is intentionally blank. iv TWDB Report ##: Structure of the Yegua-Jackson Aquifer of the Texas Gulf Coastal Plain Table of Contents Executive Summary......................................................................................................................E-i 1. Introduction......................................................................................................................... 1-1 2. Study Area and Geologic Setting.......................................................................................
    [Show full text]
  • VOLCANIC INFLUENCE OVER FLUVIAL SEDIMENTATION in the CRETACEOUS Mcdermott MEMBER, ANIMAS FORMATION, SOUTHWESTERN COLORADO
    VOLCANIC INFLUENCE OVER FLUVIAL SEDIMENTATION IN THE CRETACEOUS McDERMOTT MEMBER, ANIMAS FORMATION, SOUTHWESTERN COLORADO Colleen O’Shea A Thesis Submitted to the Graduate College of Bowling Green State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE August: 2009 Committee: James Evans, advisor Kurt Panter, co-advisor John Farver ii Abstract James Evans, advisor Volcanic processes during and after an eruption can impact adjacent fluvial systems by high influx rates of volcaniclastic sediment, drainage disruption, formation and failure of natural dams, changes in channel geometry and changes in channel pattern. Depending on the magnitude and frequency of disruptive events, the fluvial system might “recover” over a period of years or might change to some other morphology. The goal of this study is to evaluate the preservation potential of volcanic features in the fluvial environment and assess fluvial system recovery in a probable ancient analog of a fluvial-volcanic system. The McDermott Member is the lower member of the Late Cretaceous - Tertiary Animas Formation in SW Colorado. Field studies were based on a southwest-northeast transect of six measured sections near Durango, Colorado. In the field, 13 lithofacies have been identified including various types of sandstones, conglomerates, and mudrocks interbedded with lahars, mildly reworked tuff, and primary pyroclastic units. Subsequent microfacies analysis suggests the lahar lithofacies can be subdivided into three types based on clast composition and matrix color, this might indicate different volcanic sources or sequential changes in the volcanic center. In addition, microfacies analysis of the primary pyroclastic units suggests both surge and block-and-ash types are present.
    [Show full text]
  • Geology of the South-Central Pueblo Mountains, Oregon-Nevada
    AN ABSTRACT OF THE THESIS OF WINTHROP ALLEN ROWE for the MASTER OF SCIENCE (Name) (Degree) in GEOLOGY presented on lurd IL 1q4() Major) (Sate) Title: GEOLOGY OF THE SOUTH-CENTRAL PUEBLO MOUNTAINS, OREGON-NEVADA Abstract approved: Redacted for Privacy Dr. Harold E. En lows The thesis area consists of 33 square miles in the south-central Pueblo Mountains of Humboldt County, Nevada and Harney County, Oregon.The Pueblo Mountains are tilted fault block mountains found in the extreme northwestern part of the Basin and Range province and were produced during Early Tertiary Basin and Range orogeny. Northwest and northeast trending faults of Late Tertiary time have since cut the entire stratigraphic sequence. The oldest rocks exposed are metamorphosed Permian to Triassic eugeosynclinal sedimentary rocks.The metamorphic sequence is intruded by several granitic plutons of Late Jurassic to Middle Cretaceous age. A thick sequence of Miocene basalt flows unconformably overlies the pre- Tertiary rocks. A slight angular unconformity separates the basalt sequence from overlying Miocene tuffaceous sedimentary rocks, sillar flows, and welded tuffs. Unconsolidated deposits of Quaternary alluvium include alluvial fan and lacustrine sediments. Mineralization within the area includes several gold prospects, a mercury prospect, and a possible copper deposit.The copper prospect consists of a large gossan (6, 000 feet by 3, 000 feet). Mineralization and alteration from a Cretaceous porphyritic quartz monzonite intrusion has produced potassic and quartz sericite
    [Show full text]
  • Insights Into the Recurrent Energetic Eruptions That Drive Awu Among the Deadliest Volcanoes on Earth
    Insights into the recurrent energetic eruptions that drive Awu among the deadliest volcanoes on earth Philipson Bani1, Kristianto2, Syegi Kunrat2, Devy Kamil Syahbana2 5 1- Laboratoire Magmas et Volcans, Université Blaise Pascal - CNRS -IRD, OPGC, Aubière, France. 2- Center for Volcanology and Geological Hazard Mitigation (CVGHM), Jl. Diponegoro No. 57, Bandung, Indonesia Correspondence to: Philipson Bani (philipson.bani@ird.fr) 10 Abstract The little known Awu volcano (Sangihe island, Indonesia) is among the deadliest with a cumulative death toll of 11048. In less than 4 centuries, 18 eruptions were recorded, including two VEI-4 and three VEI-3 eruptions with worldwide impacts. The regional geodynamic setting is controlled by a divergent-double-subduction and an arc-arc collision. In that context, the slab stalls in the mantle, undergoes an increase of temperature and becomes prone to 15 melting, a process that sustained the magmatic supply. Awu also has the particularity to host alternatively and simultaneously a lava dome and a crater lake throughout its activity. The lava dome passively erupted through the crater lake and induced strong water evaporation from the crater. A conduit plug associated with this dome emplacement subsequently channeled the gas emission to the crater wall. However, with the lava dome cooling, the high annual rainfall eventually reconstituted the crater lake and created a hazardous situation on Awu. Indeed with a new magma 20 injection, rapid pressure buildup may pulverize the conduit plug and the lava dome, allowing lake water injection and subsequent explosive water-magma interaction. The past vigorous eruptions are likely induced by these phenomena, a possible scenario for the future events.
    [Show full text]