DOCSLIB.ORG

Numerical Evaluation and Analysis of the Occurrence of Earth Fissures in Faulted Sedimentary Basins

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Numerical Evaluation and Analysis of the Occurrence of Earth Fissures in Faulted Sedimentary Basins Numerical Evaluation and Analysis of the Occurrence of Earth Fissures in Faulted Sedimentary Basins Martin Hernandez-Marin Dissertation submitted to the faculty of the Virginia Polytechnic Institute and State University in partial fulfillment of requirements for the degree of Doctor of Philosophy in Geosciences Committee Thomas J. Burbey, Chair Madeline E. Schreiber Mark A. Widdowson Daniel L. Gallagher November 16, 2009 Blacksburg, VA Keywords: Earth fissuring, land subsidence, finite element method, ABAQUS Copyright © Martin Hernandez-Marin Numerical Evaluation and Analysis of the Occurrence of Earth Fissures in Faulted Sedimentary Basins Martin Hernandez-Marin ABSTRACT This dissertation describes the occurrence of pumping-induced earth fissures associated with quaternary faulting using numerical simulations. The Eglington Fault located in Las Vegas valley has been selected as the prototype fault described herein. The finite-element software program ABAQUS is used for the numerical simulations. The Eglington fault area is chosen because it represents one of the best examples displaying the complex relationship between fissuring, faulting and pumping-induced stress. This fault is known to influence both the vertical and horizontal deformation patterns through the accumulation of stress in its vicinity. The result is that fissures are observed on both sides of the fault and in close proximity to the fault plane. In addition to the complex fault-fissure connection, a thick caliche-rich vadose zone with weak mechanical strength allows for the initiation and propagation of fissures. The numerical analysis a) investigates the geometrical and hydromechanical features of the zone of influence surrounding the Eglington Fault; b) identifies the zones of accumulated stress on the surface and at depth that can lead to fissuring; and c) simulates the onset and propagation of tensile-induced fissures. Three-dimensional numerical simulations of this fault indicate that a 100-meter wide fault-zone composed by sand-like material best reproduces the conditions of stress that may lead to fissuring in the vicinity of the fault. Additionally, two-dimensional models reveal that two main mechanisms promote the accumulation of stress in the vicinity of the fault zone: one is the counterclockwise rotation of the unsaturated portion of the fault zone; the other is the differential compaction caused by the difference in the accumulated thickness of compressible layers. Tensile stress is concentrated on the surface in the hanging wall, but maximum shear stress zones are simulated to occur on both sides of the fault at the contact between the saturated aquifer and the vadose zone. A final analysis of the initiation and propagation of tensile-induced fissures demonstrates that fissures commence and propagate only within the vadose zone, and that the propagation path is influenced by the mechanical properties of the medium and the location of the main load, which in this case is pumping. iii DEDICATION This dissertation and all work behind it is dedicated to two exceptional persons: My dear Norma, and loved Mother. Mother, I am sure you are always taking care of me in whatever part of heaven you are now. Norma, thanks for every little thing you do for me and for every little moment you spend with me. iv ACKNOWLEDGEMENTS I want to thank my friend and advisor Thomas Burbey. Tom, thanks for accepting me as your student in the first place and thanks for guiding me toward the completion of this degree. I owe you a lot! Thanks for everything. I also thank Dr. Madeline Schreiber for her encouraging advice. Thanks, Maddy, for all your help! I also appreciate the valuable guidance and advice of my committee members Dr. Mark Widdowson and Dr. Dan Gallagher. I thank my excellent first friends of my office in Derring 3051: Isaac D. Jeng, who gave me an excellent welcome in Blacskburg along with his wonderful wife Audrey; Rachel Lauer who taught me the basics on “How to survive in the USA” along with David Rugh; I also thank my good friend Tingting from China. I will never forget the moments in class and discussion from homeworks that I spent with them, particularly with Rachel and Tingting. I thank my other old friends that left our department earlier than me: JP, Ben, Ankan, Niki and Brad, and those who continue making research: Yinka, Jeanne, Meijing, Youquan, Beth, Jonathan and Daniel. I received enormous help and friendship from them. I am very grateful to my family, specially to my lovely father and Mother. I owe them a big part of this PhD. Dear brothers, sisters and parents, thanks for all your unconditional support in whatever I decide to do in my life. The essential help on the administrative issues at Virginia Tech was provided by Connie Lowe, Mary McMurray, Linda Bland, and Carolyn Williams. I thank and congratulate all these excellent persons for doing their job very efficiently. I am especially grateful to the research group of Dr. Romesh Batra, particularly to Alireza Chadegani for spending some time giving me some crucial advice on ABAQUS. Finally, I recognize the economic support from CONACyT (National Council of Science and Technology) and our department, during most of my PhD. Also I recognize the economic help I received from the Graduate School at the end of my PhD, and I thank Dean Karen DePauw for this. v ATTRIBUTIONS This dissertation consists of three journal papers. Chapter two was published in the Hydrogeology Journal (DOI 10.1007/s10040-009-0501-8), “Hernandez-Marin, M., and Burbey. T.J., The role of faulting on surface deformation patterns from pumping-induced groundwater flow (Las Vegas Valley, USA). The concept of the project, model simulations and interpretations, writing and figure preparations were performed by M. Hernandez-Marin. T.J. Burbey clarified text and reviewed the manuscript. Chapter three was submitted for publication to the Journal of Hydrology: “Hernandez- Marin, M., and Burbey. T.J., Fault-controlled deformation and stress from pumping-induced ground-water flow in a hydrogeologic setting. The concept of the project, model simulations and interpretations, writing and figure preparations were performed by M. Hernandez-Marin. T.J. Burbey clarified text and reviewed the manuscript. Chapter four is being prepared for submission to the Hydrogeology Journal. “Hernandez- Marin, M., and Burbey. T.J., Controls on initiation and propagation of pumping-induced earth fissures: insights from numerical simulations”. The concept of the project, model simulations and interpretations, writing, and figure preparations were performed by M. Hernandez-Marin. T.J. Burbey clarified text, reviewed the manuscript and contributed with the main conclusion. vi Table of Contents Abstract……………………………………………………………………………I Dedication…………………………………………………………………………III Acknowledgments………………………………………………………………... IV Attributions……………………………………………………………………….. V Table of contents………………………………………………………………….. VI List of figures……………………………………………………………………...VIII List of tables……………………………………………………………………….X Chapter 1. Introduction…………………………………………………………… 1 Chapter 2. The role of faulting on surface deformation patterns from pumping- induced groundwater flow (Las Vegas Valley, USA)…………………………….. 3 Abstract……………………………………………………………………………4 2.1. Introduction………………………………………………………………….5 2.2. Las Vegas Valley as a prototype model……………………………………...7 2.3. Numerical modeling…………………………………………………………10 2.3.1. Conceptual models using ABAQUS……………………………………..10 2.3.2. Loads, boundary conditions and time stepping…………………………..11 2.4. Modeling results and discussion……………………………………………. 16 2.4.1. Distribution of vertical displacements at the land surface………………...16 2.4.2. Distribution of magnitudes of horizontal displacements at the land surface……………………………………………………………………20 2.4.3. Direction and evolution of horizontal displacements at the land surface.. 23 2.4.4. Surface zones under compression and tension…………………………...28 2.4.5. Model limitations and future work……………………………………… 32 2.5. Summary and conclusions………………………………………………….. 32 References………………......……………………………………………………34 Chapter 3. Fault-controlled deformation and stress from pumping-induced ground-water flow in a hydrogeologic setting…………………………………….37 Abstract……………………………………………………………………………38 3.1 Introduction…………………………………………………………………..39 3.2. Elasto-Plastic mechanical behavior………………………………………… 41 3.2.1 Poroelasticity theory……………………………………………………... 41 3.2.2 Elasto-plastic mechanical response……………………………………….44 3.3. Model Development…………………………………………………………48 3.4. Model scenarios…………………………………………………………….. 51 3.4.1. Scenarios I and II: Purely-elastic hydrostratigraphic layers………...…… 51 3.4.2. Scenarios III and VI: Elasto-plastic aquitards………………………...…. 51 3.5. Relevance of a cyclical groundwater pumping rate…………………………52 3.6. Simulated Vertical Displacement at the Land Surface………………………55 3.7. Simulated horizontal displacements………………..……………………… 56 3.7.1 Horizontal displacements on the surface and at the saturated/unsaturated interface…………………………………………………………………. 57 3.7.2 Vertical distribution of horizontal displacements in the vicinity of the fault……………………………………………………………………… 59 vii 3.8. Simulated stress…………………………………………………………….. 62 3.8.1 Distribution of tensile and compressive stress……………………………62 3.8.2 Distribution of shear stress………………………………………………..64 3.9. Discussion………………………………………………………………...….65 3.10. Conclusions…………………………………………………………………67 References………………….….……………….......………………………..……69 Chapter 4. Controls on Initiation and Propagation of pumping-induced
Load more

Recommended publications
  • Controls of Basement Fabric on Rift Coupling And
    1 2 3 4 5 This manuscript is currently undergoing peer-review. Please note that the manuscript is yet to be 6 formally accepted for publication. Subsequent versions of this manuscript may have slightly 7 different content. If accepted, the final version of this manuscript will be available via the ‘Peer- 8 reviewed Publication DOI’ link on the right-hand side of this webpage. Please feel free to contact 9 any of the authors. We look forward to your feedback. 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 1 30 CONTROLS OF BASEMENT FABRIC ON RIFT COUPLING AND DEVELOPMENT 31 OF NORMAL FAULT GEOMETRIES: INSIGHTS FROM THE RUKWA – NORTH 32 MALAWI RIFT 33 34 35 36 37 38 Erin Heilman1 39 Folarin Kolawole2 40 Estella A. Atekwana3* 41 Micah Mayle1 42 Mohamed G. Abdelsalam1 43 44 45 46 1Boone Pickens School of Geology 47 Oklahoma State University 48 Stillwater, Oklahoma, USA 49 50 2ConocoPhillips School of Geology & Geophysics 51 University of Oklahoma 52 Norman, Oklahoma, USA 53 54 3Department of Geological Sciences 55 College of Earth, Ocean, and Environment 56 University of Delaware 57 Newark, Delaware, USA 58 59 *Corresponding author email: [email protected] 60 61 62 63 64 65 66 67 68 69 70 71 72 August 2018 2 73 Highlights 74 • To the SW, newfound strike-slip fault links the Rukwa and North Malawi Rift (RNMRS) 75 • To the NE, RNMRS border faults, intervening faults and volcanic centers are colinear 76 • RNMRS border faults and transfer structures align with pre-existing basement fabrics 77 • Basement fabrics guide the development of normal fault geometries and rift bifurcation 78 • Basement fabrics facilitate the coupling of the RMRS border faults and transfer structures 79 80 81 ABSTRACT 82 The Rukwa Rift and North Malawi Rift Segments (RNMRS) both define a major rift-oblique 83 segment of the East African Rift System (EARS), and although the two young rifts show colinear 84 approaching geometries, they are often regarded as discrete rifts due to the presence of the 85 intervening Mbozi Block uplift located in-between.
    [Show full text]
  • The East African Rift System in the Light of KRISP 90
    ELSEVIER Tectonophysics 236 (1994) 465-483 The East African rift system in the light of KRISP 90 G.R. Keller a, C. Prodehl b, J. Mechie b,l, K. Fuchs b, M.A. Khan ‘, P.K.H. Maguire ‘, W.D. Mooney d, U. Achauer e, P.M. Davis f, R.P. Meyer g, L.W. Braile h, 1.0. Nyambok i, G.A. Thompson J a Department of Geological Sciences, University of Texas at El Paso, El Paso, TX 79968-0555, USA b Geophysikalisches Institut, Universitdt Karlwuhe, Hertzstrasse 16, D-76187Karlsruhe, Germany ’ Department of Geology, University of Leicester, University Road, Leicester LEl 7RH, UK d U.S. Geological Survey, Office of Earthquake Research, 345 Middlefield Road, Menlo Park, CA 94025, USA ’ Institut de Physique du Globe, Universite’ de Strasbourg, 5 Rue Ret& Descartes, F-67084 Strasbourg, France ‘Department of Earth and Space Sciences, University of California at Los Angeles, Los Angeles, CA 90024, USA ’ Department of Geology and Geophysics, University of Wuconsin at Madison, Madison, WI 53706, USA h Department of Earth and Atmospheric Sciences, Purdue University, West Lafayette, IN 47907, USA i Department of Geology, University of Nairobi, P.O. Box 14576, Nairobi, Kenya ’ Department of Geophysics, Stanford University, Stanford, CA 94305, USA Received 21 September 1992; accepted 8 November 1993 Abstract On the basis of a test experiment in 1985 (KRISP 85) an integrated seismic-refraction/ teleseismic survey (KRISP 90) was undertaken to study the deep structure beneath the Kenya rift down to depths of NO-150 km. This paper summarizes the highlights of KRISP 90 as reported in this volume and discusses their broad implications as well as the structure of the Kenya rift in the general framework of other continental rifts.
    [Show full text]
  • Plate Tectonics
    PLATE TECTONICS INTRODUCTION • Plate tectonics a unifying theory for geology • Combined 2 hypotheses: Continental drift Sea-floor spreading Early Case for Continental Drift • Continental coastlines would fit together (Wegener’s work) • Rocks & fossils indicated that continents joined Pangea- supercontinent • Combined Laurasia & Gondwanaland • Late Paleozoic glaciation • Paleoclimatology indicated apparent polar wandering • Skepticism about Continental Drift Problem of forces Paleomagnetism & Revival of Continental Drift • Magnetite aligns on existing magnetic field • Dip indicates old magnetic pole position • Apparent motion of north magnetic pole through time Split in path indicates continents split apart Recent Evidence for Continental Drift • Fitting continents at continental slope rather than shoreline • Refined matches of rocks between continents • Isotopic ages support matches • Glacial evidence • Matches between Africa and South America are particularly convincing History of Continental Positions • Pangea split up 200 m.y. (early Mesozoic) • Continents in motion for at least 2 billion years SEA-FLOOR SPREADING • Sea-floor moves away from mid-oceanic ridge • Plunges beneath continent or island arc- subduction • Rate of 1 to 6 (or more) cm/year • Driving force Originally regarded as mantle convection SEA-FLOOR SPREADING • Explanations Mid-oceanic ridge • Hot mantle rock beneath ridge High heat flow Basalt eruptions • Rift valley • Shallow-focus earthquakes Explanations Oceanic trenches • Low heat flow • Negative gravity
    [Show full text]
  • Pan-African Orogeny 1
    Encyclopedia 0f Geology (2004), vol. 1, Elsevier, Amsterdam AFRICA/Pan-African Orogeny 1 Contents Pan-African Orogeny North African Phanerozoic Rift Valley Within the Pan-African domains, two broad types of Pan-African Orogeny orogenic or mobile belts can be distinguished. One type consists predominantly of Neoproterozoic supracrustal and magmatic assemblages, many of juvenile (mantle- A Kröner, Universität Mainz, Mainz, Germany R J Stern, University of Texas-Dallas, Richardson derived) origin, with structural and metamorphic his- TX, USA tories that are similar to those in Phanerozoic collision and accretion belts. These belts expose upper to middle O 2005, Elsevier Ltd. All Rights Reserved. crustal levels and contain diagnostic features such as ophiolites, subduction- or collision-related granitoids, lntroduction island-arc or passive continental margin assemblages as well as exotic terranes that permit reconstruction of The term 'Pan-African' was coined by WQ Kennedy in their evolution in Phanerozoic-style plate tectonic scen- 1964 on the basis of an assessment of available Rb-Sr arios. Such belts include the Arabian-Nubian shield of and K-Ar ages in Africa. The Pan-African was inter- Arabia and north-east Africa (Figure 2), the Damara- preted as a tectono-thermal event, some 500 Ma ago, Kaoko-Gariep Belt and Lufilian Arc of south-central during which a number of mobile belts formed, sur- and south-western Africa, the West Congo Belt of rounding older cratons. The concept was then extended Angola and Congo Republic, the Trans-Sahara Belt of to the Gondwana continents (Figure 1) although West Africa, and the Rokelide and Mauretanian belts regional names were proposed such as Brasiliano along the western Part of the West African Craton for South America, Adelaidean for Australia, and (Figure 1).
    [Show full text]
  • Historical Background: Early Exploration in the East African Rift--The Gregory Rift Valley
    Downloaded from http://sp.lyellcollection.org/ by guest on September 26, 2021 SIR PETER KENT Historical background: Early exploration in the East African Rift--The Gregory Rift Valley In relation to modern lines of communication it seems surprising that the Gregory Rift Valley was the last part of the system to become known. Much of the earlier exploration had however been centred on the problem of the sources of the Nile, and in consequence the Western or Albertine Rift was explored by Samuel Baker as early as 1862/63 (Baker 1866). Additionally there was a strong tendency to use the convenient base at Zanzibar Island for journeys inland by the Arab slave trading routes from Pangani and Bagamoyo; these led to the Tanganyika Rift and Nyasaland rather than to the area of modern Kenya. The first penetrations into the Gregory Rift area were in I883; Joseph Thomson made an extensive journey into Central Kenya which he described in his book of 1887, 'Through Masai Land' which had as a subtitle, 'a journey of exploration among the snowclad volcanic mountains and strange tribes of Eastern Equatorial Africa--being the narrative of the Royal Geographical Society's Expedition to Mount Kenya and Lake Victoria Nyanza i883-84'. In his classic journey Thomson practically encircled the lower slopes of Mount Kilimanjaro and reached the Gregory Rift wall near the Ngong Hills. He then went north to Lake Baringo and westwards to Lake Victoria, before returning to his starting point at Mombasa. His observations on the geology were of good standard for the time.
    [Show full text]
  • The Great Rift Valley the Great Rift Valley Stretches from the Floor of the Valley Becomes the Bottom Southwest Asia Through Africa
    --------t---------------Date _____ Class _____ Africa South of the Sahara Environmental Case Study The Great Rift Valley The Great Rift Valley stretches from the floor of the valley becomes the bottom Southwest Asia through Africa. The valley of a new sea. is a long, narrow trench: 4,000 miles (6,400 The Great Rift Valley is the most km) long but only 30-40 miles (48-64 km) extensive rift on the Earth's surface. For wide. It begins in Southwest Asia, where 30 million years, enormous plates under­ it is occupied by the Jordan River and neath Africa have been pulling apart. the Dead Sea. It widens to form the basin Large earthquakes have rumbled across of the Red Sea. In Africa, it splits into an the land, causing huge chunks of the eastern and western branch. The Eastern Earth's crust to collapse. Rift extends all the way to the shores of Year after year, the crack that is the the Indian Ocean in Mozambique. Great Rift Valley widens a bit. The change is small and slow-just a few centimeters A Crack in the Ea rth Most valleys are carved by rivers, but the Great Rift Valley per year. Scientists believe that eventually is different. Violent forces in the Earth the continent will rip open at the Indian caused this valley. The rift is actually Ocean. Seawater will pour into the rift, an enormous crack in the Earth's crust. flooding it all the way north to the Red Along the crack, Africa is slowly but surely splitting in two.
    [Show full text]
  • 4. Deep-Tow Observations at the East Pacific Rise, 8°45N, and Some Interpretations
    4. DEEP-TOW OBSERVATIONS AT THE EAST PACIFIC RISE, 8°45N, AND SOME INTERPRETATIONS Peter Lonsdale and F. N. Spiess, University of California, San Diego, Marine Physical Laboratory, Scripps Institution of Oceanography, La Jolla, California ABSTRACT A near-bottom survey of a 24-km length of the East Pacific Rise (EPR) crest near the Leg 54 drill sites has established that the axial ridge is a 12- to 15-km-wide lava plateau, bounded by steep 300-meter-high slopes that in places are large outward-facing fault scarps. The plateau is bisected asymmetrically by a 1- to 2-km-wide crestal rift zone, with summit grabens, pillow walls, and axial peaks, which is the locus of dike injection and fissure eruption. About 900 sets of bottom photos of this rift zone and adjacent parts of the plateau show that the upper oceanic crust is composed of several dif- ferent types of pillow and sheet lava. Sheet lava is more abundant at this rise crest than on slow-spreading ridges or on some other fast- spreading rises. Beyond 2 km from the axis, most of the plateau has a patchy veneer of sediment, and its surface is increasingly broken by extensional faults and fissures. At the plateau's margins, secondary volcanism builds subcircular peaks and partly buries the fault scarps formed on the plateau and at its boundaries. Another deep-tow survey of a patch of young abyssal hills 20 to 30 km east of the spreading axis mapped a highly lineated terrain of inactive horsts and grabens. They were created by extension on inward- and outward- facing normal faults, in a zone 12 to 20 km from the axis.
    [Show full text]
  • Glacial-Interglacial Trench Supply Variation, Spreading-Ridge
    Glacial-interglacial trench supply variation, spreading-ridge subduction, and feedback controls on the Andean margin development at the Chile triple junction area (45-48°S) Jacques Bourgois, Christèle Guivel, Yves Lagabrielle, Thierry Calmus, Jacques Boulègue, Valérie Daux To cite this version: Jacques Bourgois, Christèle Guivel, Yves Lagabrielle, Thierry Calmus, Jacques Boulègue, et al.. Glacial-interglacial trench supply variation, spreading-ridge subduction, and feedback controls on the Andean margin development at the Chile triple junction area (45-48°S). Journal of Geo- physical Research : Solid Earth, American Geophysical Union, 2000, 105 (B4), pp.8355-8386. 10.1029/1999JB900400. hal-02497069 HAL Id: hal-02497069 https://hal.archives-ouvertes.fr/hal-02497069 Submitted on 17 Sep 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. JOURNALOF GEOPHYSICALRESEARCH, VOL. 105,NO. B4,PAGES 8355-8386, APRIL 10,2000 Glacial-interglacial trench supply variation, spreading-ridge subduction, and feedback controls on the Andean margin developmentat the Chile triple junction area (45-48øS) JacquesBourgois,• Christhie Guivel,2 Yves Lagabrielle,3Thierry Calmus,4 JacquesBoulbgue,S and Valerie Daux6 Abstract. Duringthe Chile triple junction (CTJ) cruise (March-April 1997), EM12 bathymetry andseismic reflection data were collected in thevicinity of theChile triple junction (45-48øS), wherean activespreading ridge is beingsubducted beneath the Andean continental margin.
    [Show full text]
  • Observations on Normal-Fault Scarp Morphology and Fault System Evolution of the Bishop Tuff in the Volcanic Tableland, Owens Valley, California, U.S.A
    Observations on normal-fault scarp morphology and fault system evolution of the Bishop Tuff in the Volcanic Tableland, Owens Valley, California, U.S.A. David A. Ferrill, Alan P. Morris, Ronald N. McGinnis, Kevin J. Smart, Morgan J Watson-Morris, and Sarah S. Wigginton DEPARTMENT OF EARTH, MATERIAL, AND PLANETARY SCIENCES, SOUTHWEST RESEARCH INSTITUTE®, 6220 CULEBRA ROAD, SAN ANTONIO, TEXAS 78238, USA ABSTRACT Mapping of normal faults cutting the Bishop Tuff in the Volcanic Tableland, northern Owens Valley, California, using side-looking airborne radar data, low-altitude aerial photographs, airborne light detection and ranging (LiDAR) data, and standard field mapping yields insights into fault scarp development, fault system evolution, and timing. Fault zones are characterized by multiple linked fault segments, tilting of the welded ignimbrite surface, dilation of polygonal cooling joints, and toppling of joint-bounded blocks. Maximum fault zone width is governed by (i) lateral spacing of cooperating fault segments and (ii) widths of fault tip monoclines. Large-displacement faults interact over larger rock volumes than small-displacement faults and generate larger relay ramps, which, when breached, form the widest portions of fault zones. Locally intense faulting within a breached relay ramp results from a combination of distributed east-west extension, and within- ramp bending and stretching to accommodate displacement gradients on bounding faults. One prominent fluvial channel is offset by both east- and west-dipping normal faults such that the channel is no longer in an active flowing configuration, indicating that channel incision began before development of significant fault-related geomorphic features. The channel thalweg is “hanging” with respect to modern (Q1) and previous (Q2) Owens River terraces, is incised through the pre-Tahoe age terrace level (Q4, 131–463 ka), and is at grade with the Tahoe age (Q3, 53–119 ka) terrace.
    [Show full text]
  • Rift-Valley-1.Pdf
    R E S O U R C E L I B R A R Y E N C Y C L O P E D I C E N T RY Rift Valley A rift valley is a lowland region that forms where Earth’s tectonic plates move apart, or rift. G R A D E S 6 - 12+ S U B J E C T S Earth Science, Geology, Geography, Physical Geography C O N T E N T S 9 Images For the complete encyclopedic entry with media resources, visit: http://www.nationalgeographic.org/encyclopedia/rift-valley/ A rift valley is a lowland region that forms where Earth’s tectonic plates move apart, or rift. Rift valleys are found both on land and at the bottom of the ocean, where they are created by the process of seafloor spreading. Rift valleys differ from river valleys and glacial valleys in that they are created by tectonic activity and not the process of erosion. Tectonic plates are huge, rocky slabs of Earth's lithosphere—its crust and upper mantle. Tectonic plates are constantly in motion—shifting against each other in fault zones, falling beneath one another in a process called subduction, crashing against one another at convergent plate boundaries, and tearing apart from each other at divergent plate boundaries. Many rift valleys are part of “triple junctions,” a type of divergent boundary where three tectonic plates meet at about 120° angles. Two arms of the triple junction can split to form an entire ocean. The third, “failed rift” or aulacogen, may become a rift valley.
    [Show full text]
  • Surficial-Geologic Reconnaissance and Scarp Profiling on The
    Surficial-Geologic Reconnaissance and Scarp Profiling on the Collinston and Clarkston Mountain Segments of the Wasatch Fault Zone, Box Elder County, Utah – Paleoseismic Inferences, Implications for Adjacent Segments, and Issues for Diffusion-Equation Scarp-Age Modeling Paleoseismology of Utah, Volume 15 By Michael D. Hylland SPECIAL STUDY 121 UTAH GEOLOGICAL SURVEY a division of Utah Department of Natural Resources 2007 Surficial-Geologic Reconnaissance and Scarp Profiling on the Collinston and Clarkston Mountain Segments of the Wasatch Fault Zone, Box Elder County, Utah – Paleoseismic Inferences, Implications for Adjacent Segments, and Issues for Diffusion-Equation Scarp-Age Modeling Paleoseismology of Utah, Volume 15 By Michael D. Hylland ISBN 1-55791-763-9 SPECIAL STUDY 121 UTAH GEOLOGICAL SURVEY a division of Utah Department of Natural Resources 2007 STATE OF UTAH Jon Huntsman, Jr., Governor DEPARTMENT OF NATURAL RESOURCES Michael Styler, Executive Director UTAH GEOLOGICAL SURVEY Richard G. Allis, Director PUBLICATIONS contact Natural Resources Map/Bookstore 1594 W. North Temple Salt Lake City, UT 84116 telephone: 801-537-3320 toll-free: 1-888-UTAH MAP Web site: http://mapstore.utah.gov email: [email protected] THE UTAH GEOLOGICAL SURVEY contact 1594 W. North Temple, Suite 3110 Salt Lake City, UT 84116 telephone: 801-537-3300 fax: 801-537-3400 Web site: http://geology.utah.gov Although this product represents the work of professional scientists, the Utah Department of Natural Resources, Utah Geological Survey, makes no war- ranty, expressed or implied, regarding its suitability for a particular use. The Utah Department of Natural Resources, Utah Geological Survey, shall not be liable under any circumstances for any direct, indirect, special, incidental, or consequential damages with respect to claims by users of this product.
    [Show full text]
  • Anatomy of Rifting: Tectonics and Magmatism in Continental Rifts, Oceanic Spreading Centers, and Transforms GEOSPHERE; V
    Research Note THEMED DownloadedISSUE: Anatomy from of geosphere.gsapubs.org Rifting: Tectonics and Magmatism on January in 13, Continental 2016 Rifts, Oceanic Spreading Centers, and Transforms GEOSPHERE Introduction: Anatomy of rifting: Tectonics and magmatism in continental rifts, oceanic spreading centers, and transforms GEOSPHERE; v. 11, no. 5 Carolina Pagli1, Francesco Mazzarini2, Derek Keir3, Eleonora Rivalta4, and Tyrone O. Rooney5 1Dipartimento di Scienze della Terra, Università di Pisa, Via S. Maria 53, 56126 Pisa, Italy doi:10.1130/GES01082.1 2Istituto Nazionale di Geofisica e Vulcanologia, Sezione di Pisa, Via della Faggiola 32, 56100, Pisa, Italy 3National Oceanography Centre Southampton, University of Southampton, Waterfront Campus, European Way, Southampton, Hampshire SO14 3ZH, UK 2 figures 4Helmholtz-Zentrum Potsdam Deutsches GeoForschungsZentrum (GFZ), Telegrafenberg, 14473 Potsdam, Germany 5Department of Geological Sciences, Michigan State University, 288 Farm Lane, East Lansing, Michigan 48824, USA CORRESPONDENCE: [email protected] ABSTRACT 2001). Magma intrusions thermally weaken the plate (Daniels et al., 2014), while CITATION: Pagli, C. Mazzarini, F., Keir, D., Rivalta, magma overpressure alters the stress field, facilitating extension at relatively E., and Rooney, T.O., 2015, Introduction: Anatomy of rifting: Tectonics and magmatism in continental Research at continental rifts, mid-ocean ridges, and transforms has shown low forces (Bialas et al., 2010). At most mid-ocean ridges, magma intrusions rifts, oceanic spreading centers, and transforms: that new plates are created by extensional tectonics, magma intrusion, and accommodate the majority of extension (Delaney et al., 1998; Sigmundsson, Geosphere, v. 11, no. 5, p. 1256–1261, doi: 10 .1130 volcanism. Studies of a wide variety of extensional processes ranging from 2006; Wright et al., 2012); however, mechanical faulting remains an important /GES01082.1.
    [Show full text]