Fall 2019 (Pdf)
Total Page:16
File Type:pdf, Size:1020Kb

Load more
Recommended publications
-
38. Effect of Axial Magma Chambers Beneath Spreading Centers on the Compositions of Basaltic Rocks
38. EFFECT OF AXIAL MAGMA CHAMBERS BENEATH SPREADING CENTERS ON THE COMPOSITIONS OF BASALTIC ROCKS James H. Natland, Scripps Institution of Oceanography, La Jolla, California ABSTRACT Ferrobasalts are among a range of basalt types erupted over large, shallow, axial magma chambers beneath the East Pacific Rise crest near 9°N, and the Galapagos Rift near 86°W. Geological and geo- chemical evidence indicates that they evolve in small, isolated magma bodies either in conduit systems over the chambers, or in the solidify- ing walls of the magma chamber flanks away from the loci of fissure eruptions. The chambers act mainly as buffers in which efficient mix- ing ensures that a uniform average, moderately fractionated parent is supplied to the range of magma types erupted at the sea floor. For- mation of ferrobasalts in isolated magma bodies prevents them from mixing directly with primitive olivine tholeiite supplied to the base of the East Pacific Rise magma chamber at 9°N. Rises with abundant ferrobasalts may have magma chambers with broad, flat tops over which eruptions occur in wide, probably struc- turally unstable rift zones. Rises without ferrobasalts may have magma chambers with tapered tops which persistently constrain eruptions to narrow fissure zones, preventing formation of isolated shallow magma bodies where ferrobasalts can evolve. Formation of a flat-topped, rather than a tapered, magma chamber may reflect a high rate of magma supply relative to spreading rate. Steady-state compositions can be approached in magma cham- bers, probably approximating the least-fractionated typical lavas erupted above them. On this basis, the bulk magma composition in the chamber beneath the Galapagos Rift has become more iron-rich through time, a consequence of magma migration eastward down the rift as it shoaled to the west under the influence of the Galapagos Island hot spot. -
2007 Medals & Awards Rip Rapp Archaeological Geology Award
2007 MEDALS & AWARDS RIP RAPP the many sources of ancient white marble There have now been eight international in the Mediterranean, Norm worked to find ASMOSIA conferences bringing together ARCHAEOLOGICAL an analytical technique that was at one end a truly interdisciplinary group of scholars GEOLOGY AWARD objective and at another end required very including geochemists, geologists, chemists, little sample. Norm found that technique by physicists, statisticians, archaeologists, Presented to Norman Herz delving into the measurement of carbon and museum curators, art historians and others oxygen stable isotopes. From the late 1970s who share research interests and perspectives through the 1980s, Norm went on “arduous” on ancient stone. By maintaining a single expeditions to collect multiple samples from session format the ASMOSIA meetings the important ancient marble quarries in promote a true interdisciplinary exchange Turkey, Greece and Italy. Working alongside of ideas and research between scholars from archaeologists and art historians, Norm was diverse academic backgrounds. Since that able to show that many quarries had unique first meeting of 53 participants, ASMOSIA’s stable isotope signatures. Norm was able to membership has grown to over 300 from assign provenance to many marble artifacts over 23 countries. The continued success and address important questions regarding of the biennial ASMOSIA conferences is the use, trade and quarrying of this important an excellent testament to Norm’s vision ancient resource. Norm has consulted on and leadership in fostering interdisciplinary numerous projects including studying the research. Norm saw the need for true marble sources of various temples and collaboration across academic fields long monuments at sites such as ancient Olympia, before multidisciplinary and interdisciplinary Bassai, the Athenian Agora, and Delos. -
Geochemistry and Origin of Middle Miocene Volcanic Rocks from Santa Cruz and Anacapa Islands, Southern California Borderland Peter W
Geochemistry and Origin of Middle Miocene Volcanic Rocks from Santa Cruz and Anacapa Islands, Southern California Borderland Peter W. Weigand Department of Geological Sciences California State University Northridge, CA 91330 Cenozoic volcanism that began in the eastern Abstract - Major-oxide and trace-element Mojave Desert about 30 m.y. ago and swept compositions of middle Miocene volcanic rocks irregularly west and north. This extensive from north Santa Cruz and Anacapa Islands are extrusive activity was related closely to complex very similar. In contrast, they are geochemically tectonic activity that included subduction of the distinct from the volcanic clasts from the Blanca Farallon plate whose subduction angle was Formation, of similar age but located south of steepening, and interaction of the Pacific and the Santa Cruz Island fault, which implies North American plates along a lengthening significant strike-slip movement on this fault. transform boundary; this activity additionally The island lavas are also compositionally involved rotation and possible northward distinct from the Conejo Volcanics located translation of crustal blocks. onshore in the Santa Monica Mountains. The The origin of the volcanic rocks in this area island lavas are part of a larger group of about has been variously ascribed to subduction of the 12 similar-aged volcanic suites from the Farallon plate (Weigand 1982; Crowe et al. California Borderland and onshore southern 1976; Higgins 1976), subduction of the Pacific- California that all belong to the calc-alkaline -
Deep-Tow Studies of the Structure of the Mid-Atlantic Ridge Crest Near Lat 37°N
Deep-tow studies of the structure of the Mid-Atlantic Ridge crest near lat 37°N KEN C. MACDONALD* Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, La Jolla, California 92093 BRUCE P. LUYENDYK Department of Geological Sciences, University of California, Santa Barbara, California 93106 This article is one of a series appearing in the April and May issues of the Geological Society of America Bulletin on the scientific results of Project FAMOUS. These studies were undertaken in the axial area of the Mid-Atlantic Ridge between approximately 36°30' and 37°N latitudes. ABSTRACT large faulted blocks toward nearby fracture Le Pichon, 1974). We discuss here the de- zones suggests that spreading-center tec- tailed structure and evolution of the rift val- A detailed study of the structure of the tonics is affected by fracture-zone tectonics leys between fracture zones A and B (rift Mid-Atlantic Ridge median valley and rift throughout the length of the rift in the valley 2) and B and C (rift valley 3) and the mountains near lat 37°N (FAMOUS) was FAMOUS area. Both the crustal accretion rift mountains in these areas. Fine-scale conducted using a deep-tow instrument zone and transform fault zone are narrow, deep-tow studies of the inner floor of rift package. The median valley may have either only 1 to 2 km wide, over short periods of valley 2 are discussed by Luyendyk and a very narrow inner floor (1 to 4 km) and time. In the course of millions of years, how- Macdonald (1977). -
Ocean-Bottom Seismograph Observations on the Mid-Atlantic Ridge Near Lat 37°N
Ocean-bottom seismograph observations on the Mid-Atlantic Ridge near lat 37°N T.J.G. FRANCIS* Cooperative Institute for Research in Environmental Sciences, University of ColoradolNOAA, Boulder, Col- orado 80309 I. T. PORTER Institute of Oceanographic Sciences, Blacknest, Brimpton, Reading, RG7 4TJ England J. R. McGRATH U.S. Naval Research Laboratory, Washington, D.C. 20390 This article is one of a series appearing in the April and May issues of the Geological Society of America Bulletin on the scientific results of Project FAMOUS. These studies were undertaken in the axial area of the Mid-Atlantic Ridge between approximately 36°30' and 37°N latitudes. ABSTRACT 200 Hz. The tape speed of the recording system used by the ocean-bottom seismographs set an upper limit of about 40 Hz to Ocean-bottom seismographs were deployed twice in the FA- the frequencies recorded. It was decided to retain the original hyd- MOUS area in 1973. Few earthquakes were observed on the first rophones of the seismographs as well to be able to compare the per- occasion, but 515 were recorded on the second with magnitudes formance of the two systems. Since only four data channels can be ranging from 0 to 2.5. These occurred both in the median valley recorded in each ocean-bottom seismograph, the H-58 hydrophone and in the fracture zone adjacent to the instruments. The latter was substituted for one of the horizontal seismometers. Thus dur- events have been interpreted as activity along a single Riedel frac- ing the October 1973 deployment, each instrument recorded the ture cutting obliquely across the trend of the fracture zone. -
Results from Camera Tows Along the Southern Juan De Fuca Ridge
UNITED STATES DEPARTMENT OF THE INTERIOR GEOLOGICALSURVEY Results From Camera Tows Along the Southern Juan de Fuca Ridge: A2-84-WF Ellen S. Kappel1 ' 2 and William R. Normark1 Open-File Report 88-371 This report is preliminary and has not been reviewed for conformity with U. S. Geological Survey editorial standards and stratigraphic nomenclature. Any use of trade names is for descriptive purposes only and does not imply endorsement by the USGS. 1 U. S. Geological Survey, Menlo Park, California 2 Now at Joint Oceanographic Institutions Incorporated, Washington, D. C. ABSTRACT Nine camera tows carried out along the southern Juan de Fuca Ridge during the summer of 1984 extended photographic and video coverage north of the main USGS study area. These data, together with one camera tow conducted outside of the axial valley, provide ground-truth data for Sea MARC I and II acoustic images of the ridge axial zone. In addition, four new hydrothermal vents were discovered within the axial valley between latitudes 44°43'N and 44°54'N. INTRODUCTION The Juan de Fuca Ridge (JdFR) is a medium-rate (full spreading rate of 6 cm/yr) oceanic spreading center located approximately 500 km off the coasts of Oregon and Washington in the northeast Pacific Ocean (Figure 1). The ridge extends for nearly 500 km between the Blanco and Sovanco transform faults and separates the Pacific Plate from the Juan de Fuca Plate. Discoveries of high temperature hydrothermal venting, associated sulfide deposits, and unusual biota along the neovolcanic zones of medium-rate Pacific spreading centers ,such as the Galapagos Spreading Center (Ballard and others, 1982) and the East Pacific Rise at 21 °N (CYAMEX Scientific Team, 1979; RISE Project Group, 1980), prompted scientists from the U.S. -
When the Earth Moves Seafloor Spreading and Plate Tectonics
This article was published in 1999 and has not been updated or revised. BEYONDBEYOND DISCOVERYDISCOVERYTM THE PATH FROM RESEARCH TO HUMAN BENEFIT WHEN THE EARTH MOVES SEAFLOOR SPREADING AND PLATE TECTONICS arly on the morning of Wednesday, April 18, the fault had moved, spanning nearly 300 miles, from 1906, people in a 700-mile stretch of the West San Juan Bautista in San Benito County to the south E Coast of the United States—from Coos Bay, of San Francisco to the Upper Mattole River in Oregon, to Los Angeles, California—were wakened by Humboldt County to the north, as well as westward the ground shaking. But in San Francisco the ground some distance out to sea. The scale of this movement did more than shake. A police officer on patrol in the was unheard of. The explanation would take some six city’s produce district heard a low rumble and saw the decades to emerge, coming only with the advent of the street undulate in front of him, “as if the waves of the theory of plate tectonics. ocean were coming toward me, billowing as they came.” One of the great achievements of modern science, Although the Richter Scale of magnitude was not plate tectonics describes the surface of Earth as being devised until 1935, scientists have since estimated that divided into huge plates whose slow movements carry the the 1906 San Francisco earthquake would have had a continents on a slow drift around the globe. Where the 7.8 Richter reading. Later that morning the disaster plates come in contact with one another, they may cause of crushed and crumbled buildings was compounded by catastrophic events, such as volcanic eruptions and earth- fires that broke out all over the shattered city. -
Spatial and Temporal Distribution of Seismicity Along the Northern Mid-Atlantic Ridge (15°–35°N) Deborah K
JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 108, NO. B3, 2167, doi:10.1029/2002JB001964, 2003 Spatial and temporal distribution of seismicity along the northern Mid-Atlantic Ridge (15°–35°N) Deborah K. Smith,1 Javier Escartin,2 Mathilde Cannat,2 Maya Tolstoy,3 Christopher G. Fox,4 DelWayne R. Bohnenstiehl,3 and Sara Bazin2 Received 8 May 2002; revised 16 September 2002; accepted 8 November 2002; published 25 March 2003. [1] A detailed investigation of the relationship between the spatial and temporal patterns of the seismic activity recorded by six autonomous hydrophones and the structure of the northern Mid-Atlantic Ridge between 15° and 35°N is presented. Two years of monitoring yielded a total of 3485 hydroacoustically detected events within the array recorded by four or more hydrophones. The seismically active zone extends 20 km to either side of the ridge axis, consistent with earlier results from studies of fault morphology. Along the axis, hydrophone-recorded activity shows important variations. Areas with intense and persistent seismic activity (stripes) stand in sharp contrast to areas that lack seismicity (gaps). The regions of persistent activity are a new observation at mid-ocean ridges. In general, the patterns of seismically active/inactive regions are also recognized in the 28-year teleseismic record, implying that these patterns are maintained at timescales between a few years and a few decades. We find no simple relationship between individual segment variables (e.g., length or trend of the segment, maximum offset of discontinuities, or along-axis change in mantle Bouguer anomaly (MBA) and water depths) and number of hydrophone-recorded events. -
WOODS HOLE OCEANOGRAPHIC INSTITUTION Deep-Diving
NEWSLETTER WOODS HOLE OCEANOGRAPHIC INSTITUTION AUGUST-SEPTEMBER 1995 Deep-Diving Submersible ALVIN WHOI Names Paul Clemente Sets Another Dive Record Chief Financial Officer The nation's first research submarine, the Deep Submergence Paul CI~mente, Jr., a resident of Hingham Vehicle (DSV) Alvin. passed another milestone in its long career and former Associate Vice President for September 20 when it made its 3,OOOth dive to the ocean floor, a Financial Affairs at Boston University, as· record no other deep-diving sub has achieved. Alvin is one of only sumed his duties as Associate Director for seven deep-diving (10,000 feet or more) manned submersibles in the Finance and Administration at WHOI on world and is considered by far the most active of the group, making October 2. between 150 and 200 dives to depths up to nearly 15,000 feet each In his new position Clemente is respon· year for scientific and engineering research . sible for directing all business and financial The 23-1001, three-person submersible has been operated by operations of the Institution, with specifIC Woods Hole Oceanographic Institution since 1964 for the U.S. ocean resp:>nsibility for accounting and finance, research community. It is owned by the OffICe of Naval Research facilities, human resources, commercial and supported by the Navy. the National Science Foundation and the affairs and procurement operations. WHOI, National Oceanic and Atmospheric Administration (NOAA). Alvin the largest private non· profit marine research and its support vessel, the 21 0-100t Research Vessel Atlantis II, are organization in the U.S., has an annual on an extended voyage in the Pacific which began in January 1995 operating budget of nearly $90 million and a with departure from Woods Hole. -
The North American Cordillera from Tanya Atwater to Karin Sigloch Paul F
Document generated on 09/29/2021 4:27 a.m. Geoscience Canada The Tooth of Time: The North American Cordillera from Tanya Atwater to Karin Sigloch Paul F. Hoffman Volume 40, Number 2, 2013 URI: https://id.erudit.org/iderudit/geocan40_2col01 See table of contents Publisher(s) The Geological Association of Canada ISSN 0315-0941 (print) 1911-4850 (digital) Explore this journal Cite this document Hoffman, P. F. (2013). The Tooth of Time:: The North American Cordillera from Tanya Atwater to Karin Sigloch. Geoscience Canada, 40(2), 71–93. All rights reserved © The Geological Association of Canada, 2013 This document is protected by copyright law. Use of the services of Érudit (including reproduction) is subject to its terms and conditions, which can be viewed online. https://apropos.erudit.org/en/users/policy-on-use/ This article is disseminated and preserved by Érudit. Érudit is a non-profit inter-university consortium of the Université de Montréal, Université Laval, and the Université du Québec à Montréal. Its mission is to promote and disseminate research. https://www.erudit.org/en/ GEOSCIENCE CANADA Volume 40 2013 71 COLUMN The Tooth of Time: batholith; R.V. Fisher and Bill Wise, Not long after, he became legendary the Cenozoic volcanic fields; and Pres for a different reason. As a Richfield The North American Cloud, the Death Valley area. Yet all Oil Corporation geologist, Natland Cordillera from Tanya the trips had one thing in common: proposed that detonating up to 100 Atwater to Karin Sigloch sooner or later, at every stop, the talk underground nuclear devices (atomic would turn to Tanya. -
Petrogenetic Study of the Porcupine Lake Mafic Intrusive Complex, Trinity Terrane, Northern California
UNLV Retrospective Theses & Dissertations 1-1-2000 Petrogenetic study of the Porcupine Lake mafic intrusive complex, Trinity terrane, northern California Edward Robert Muller University of Nevada, Las Vegas Follow this and additional works at: https://digitalscholarship.unlv.edu/rtds Repository Citation Muller, Edward Robert, "Petrogenetic study of the Porcupine Lake mafic intrusive complex, Trinity terrane, northern California" (2000). UNLV Retrospective Theses & Dissertations. 1171. http://dx.doi.org/10.25669/tnq4-ppc2 This Thesis is protected by copyright and/or related rights. It has been brought to you by Digital Scholarship@UNLV with permission from the rights-holder(s). You are free to use this Thesis in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s) directly, unless additional rights are indicated by a Creative Commons license in the record and/ or on the work itself. This Thesis has been accepted for inclusion in UNLV Retrospective Theses & Dissertations by an authorized administrator of Digital Scholarship@UNLV. For more information, please contact [email protected]. INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter ^ ce , while others may be from any type of computer printer. The quality of this reproduction is dependent upon the quality of the copy subm itted. Broken or irxlistnct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. -
Renowned Researcher Discusses Plate Tectonics
University of Montana ScholarWorks at University of Montana University of Montana News Releases, 1928, 1956-present University Relations 3-21-2005 Renowned researcher discusses plate tectonics University of Montana--Missoula. Office of University Relations Follow this and additional works at: https://scholarworks.umt.edu/newsreleases Let us know how access to this document benefits ou.y Recommended Citation University of Montana--Missoula. Office of University Relations, "Renowned researcher discusses plate tectonics" (2005). University of Montana News Releases, 1928, 1956-present. 19075. https://scholarworks.umt.edu/newsreleases/19075 This News Article is brought to you for free and open access by the University Relations at ScholarWorks at University of Montana. It has been accepted for inclusion in University of Montana News Releases, 1928, 1956-present by an authorized administrator of ScholarWorks at University of Montana. For more information, please contact [email protected]. <^v m ^ The University of W M ontana UNIVERSITY RELATIONS • MISSOULA, MT 59812 • 406-243-2522 • FAX: 406-243-4520 March 21, 2005 Contact: UM Assistant Professor Emmanuel Gabet, Department of Geology, (406) 243-4024. RENOWNED RESEARCHER DISCUSSES PLATE TECTONICS MISSOULA- Tanya Atwater, tectonics professor at the University of California, Santa Barbara, will discuss the tectonic evolution of western North America when she visits The University of Montana Tuesday, March 29. Her lecture, “Plate Tectonic Evolution of Western North America,” will take place at 4 p.m. in Science Complex Room 131 and features slides and computer animation. The event is free and open to the public. Atwater has been instrumental in advancing the concept of plate tectonics and has spent the past several years developing computer animations to illustrate tectonic processes.