DOCSLIB.ORG

Did the 1999 Earthquake Swarm on Gakkel Ridge Open a Volcanic Conduit? a Detailed Teleseismic Data Analysis Carsten Riedel, Vera Schlindwein

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Did the 1999 Earthquake Swarm on Gakkel Ridge Open a Volcanic Conduit? a Detailed Teleseismic Data Analysis Carsten Riedel, Vera Schlindwein Did the 1999 earthquake swarm on Gakkel Ridge open a volcanic conduit? A detailed teleseismic data analysis Carsten Riedel, Vera Schlindwein To cite this version: Carsten Riedel, Vera Schlindwein. Did the 1999 earthquake swarm on Gakkel Ridge open a volcanic conduit? A detailed teleseismic data analysis. Journal of Seismology, Springer Verlag, 2009, 14 (3), pp.505-522. 10.1007/s10950-009-9179-6. hal-00537995 HAL Id: hal-00537995 https://hal.archives-ouvertes.fr/hal-00537995 Submitted on 20 Nov 2010 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. J Seismol (2010) 14:505–522 DOI 10.1007/s10950-009-9179-6 ORIGINAL ARTICLE Did the 1999 earthquake swarm on Gakkel Ridge open a volcanic conduit? A detailed teleseismic data analysis Carsten Riedel · Vera Schlindwein Received: 19 February 2009 / Accepted: 2 November 2009 / Published online: 20 November 2009 © Springer Science + Business Media B.V. 2009 Abstract In 1999, a seismic swarm of 237 tele- ascending toward the potential conduit during the seismically recorded events marked a submarine beginning of April 1999, indicating an opening of eruption along the Arctic Gakkel Ridge, later on the vent. also analyzed by sonar, bathymetric, hydrother- mal, and local seismic studies. We relocated the Keywords Gakkel Ridge · HYPOSAT · swarm with the global location algorithm HY- Relocation · Station residuals · Spatiotemporal POSAT and analyzed the waveforms of the sta- organization · 1999 swarm · Polar research · tions closest to the events by cross-correlation. Double difference · Cross-correlation · Magma We find event locations scattered around 85◦35 ascent · Oden volcano · Ultraslow-spreading ridge Nand85◦ E at the southern rift wall and inside the rift valley of the Gakkel Ridge. Waveforms of three highly correlating events indicate a vol- 1 Introduction umetric moment tensor component and highly precise referenced double-difference arrival times The Arctic Gakkel Ridge (Fig. 1) is one of the lead us to believe that they occur at the same slowest-spreading zones of the Earth’s lithosphere geographical position and mark the conduit lo- (Dick et al. 2003) with a full spreading rate lower cated further southeast close to a chain of recently than 1.2 cm/year. Along the rift axis, volcanic and imaged volcanic cones. This result is supported amagmatic units alternate (Michael et al. 2003). by station residual anomalies in the direction of Details of the active rifting processes are still the potential conduit. Seismicity is focused at the unknown due to the remote location of Gakkel crust–mantle boundary at 16–20 km depth, but Ridge and its cover with Arctic sea ice which only few research vessels can tackle. However, in 1999, a sequence of earthquakes of body wave C. Riedel (B) · V. Schlindwein magnitude 3.3 (International Seismological Cen- Alfred-Wegener-Institut für Polar- und tre [ISC]) and higher was recorded worldwide Meeresforschung, Am alten Hafen 26, 27568, Bremerhaven, Germany (Müller and Jokat 2000; Tolstoy et al. 2001), which e-mail: [email protected] is so far the largest teleseismically recorded earth- quake swarm at any mid-ocean ridge (MOR) vol- Present Address: canic system and occurred in the area surrounding C. Riedel ◦ ◦ KGS Rastede, WIlhelmstr. 5, 85 40 N, 85 E (Fig. 1). Global centroid moment 26180 Rastede, Germany tensor solutions with large isotropic components 506 J Seismol (2010) 14:505–522 270˚ 240˚ 300˚ 210˚ 330˚ 80˚ 85 m below sea surface ˚48' 82˚ 84˚ 86˚ 0˚ 88˚ 90˚ 180˚ 85˚48' 30˚ 150˚ 85˚36' 60 ˚ ˚ 120 90˚ 85˚36' 70 60 50 85˚24' 40 85˚24' 30 km 20 0 5 10 10 85˚12' 80˚ 0 82˚ 3 4 5 6 84˚ 86˚ 85˚12' 88˚ 90˚ Fig. 1 The ISC locations of the 237 events mentioned size of the circles in the location graph is proportional to in the text have been plotted as dark gray circles on a the square values of magnitude (scale see below magnitude bathymetric map of Gakkel Ridge in the survey area on distribution) to ease the view of high-magnitude events. the left side of the figure. A scale for the bathymetry where A small white triangle (volcano) marks the position of the black is related to topographic lows and white is related to crater of Oden volcano which was discovered by Sohn topographic highs is displayed at the top. On the right side et al. (2008). All figures including this one have been the position of the swarm area is marked as a white box plotted using Generic Mapping Tools (Wessel and Smith on a plot of the high latitudinal areas of the northern hemi- 1998) sphere. Below, a histogram of magnitudes is presented. The and high b values indicated a typical volcanic (Schlindwein et al. 2005; Schlindwein and Riedel character (Müller and Jokat 2000) and sonar im- 2009) even 2 years after the major earthquake ages from the USS Hawkbill only 4 months after swarm. In 2007, the AGAVE cruise revealed thick the main activity showed areas of high backscatter blankets of volcaniclastic sediments in the area interpreted as fresh lava flows (Edwards et al. which contain Limu o Pele, i.e., very thin glassy 2001). crystallized rims of gas bubbles in magma and, During the joint AMORE 2001 cruise on the thus, clear evidence for considerable explosive USCGC Healy and RV Polarstern rock sampling, volcanism at water depths of about 4,000 m and bathymetric surveys and hydrothermal studies dis- a chain of small volcanic peaks with Oden volcano covered that the seismically active area repre- (white triangle in Fig. 1) at its easternmost loca- sents a major volcanic complex (Michael et al. tion (Sohn et al. 2008). 2003). A giant hydrothermal plume in the wa- While MOR volcanism is generally considered ter column indicated sustained volcanic activity to be effusive, the relevance of explosive erup- (Edmonds et al. 2003; Baker et al. 2004). A local tions at MORs has only recently been recognized seismic experiment with seismic arrays on ice floes (Clague et al. 2008). Understanding the seismo- recorded a swarm of sea bottom explosive signals volcanic episode at the 85◦ E volcanic complex J Seismol (2010) 14:505–522 507 at Gakkel Ridge may, therefore, yield valuable ability of data for some of the decisive events from new information on deep submarine eruption stations farther east is scarce. Thus, we have rela- processes. In this light, we intensively analyze tively huge azimuthal gaps for waveform analysis the teleseismically recorded earthquake swarm and did not try a reanalysis of moment tensor of 1999, relocating it with an advanced classical solutions. location tool, HYPOSAT, using various veloc- ity models and exploring new ways of describ- ing the dataset in terms of its spatiotemporal 3 Methods and results organization. 3.1 HYPOSAT locations of the swarm events 2 Dataset After intercomparison with several other loca- tion tools such as HYPO71 (Lee and Lahr 1975), We used all seismic events between January and HYPOCENTER (Lienert and Havskov 1995), September 1999 registered in the ISC online bul- and ISCloc (Luckett and Storchak 2001), we used letins (we downloaded them on the 6 September HYPOSAT (Schweitzer 2001) as one of the ad- 2007 from http://www.isc.ac.uk)inanareafrom vanced classical global location tools for reloca- 85◦ Nto87◦ Nand70◦ Eto95◦ E. This dataset tion of the swarm: is not completely identical to previous studies – It is classical in the way it uses the Geiger (Müller and Jokat 2000; Tolstoy et al. 2001), which method for locating earthquakes. used a preliminary dataset available at that time. – It allows the selection of confidence levels for Our dataset contains 237 events in contrast to 252 error ellipses that we chose as 95%, the error events of Tolstoy et al. (2001) with body wave is handled as rms values as well as distance magnitudes (m ) between 3.3 and 5 (Fig. 1). b errors in all spatial directions. The original dataset was located using ISCloc – It documents the search for location solu- in the ISC standard procedures as outlined in tions far away from solutions already found Storchak (2006) using the Jeffreys–Bullen travel in previous iterations and thus documents the time tables and a complicated weighting scheme robustness of the hypocenter solution (better that delivers unrealistically small errors. The root than HYPOCENTER). mean square (rms) travel time residual for the – It uses an arbitrary regional velocity model original dataset is ∼1.14 s with only four of these and can also use a global velocity model events not fixed in depth. in farther distances from the source location For further analysis, we also inspected pub- (better than ISCloc). In our case, we used licly available waveforms of the nearest stations the IASPEI-91-model (IASP91; Kennett and that recorded the events (see Fig. 2), taking Engdahl 1991; Kennett et al. 1995)orthe care to realize an equiazimuthal coverage. This preliminary reference earth model (PREM; set of waveforms includes data from the North Dziewonski and Anderson 1981) which has Atlantic sector (Kings Bay [KBS], Spitsbergen ar- been shown to work better in marine en- ray [SPITS], Daneborg–Greenland [DAG], North vironments (Reves-Sohn, personal communi- Norway [ARCES], and Lovozero–European Rus- cation) as the global model.
Load more

Recommended publications
  • Description of Map Units Northeast Asia Geodynamics Map
    DESCRIPTION OF MAP UNITS NORTHEAST ASIA GEODYNAMICS MAP OVERLAP ASSEMBLAGES (Arranged alphabetically by map symbol) ad Adycha intermountain sedimentary basin (Miocene and Pliocene) (Yakutia) Basin forms a discontinuous chain along the foot of southwestern slope of Chersky Range in the Yana and Adycha Rivers basins. Contain Miocene and Pliocene sandstone, pebble gravel conglomerate, claystone, and minor boulder gravel conglomerate that range up to 400 m thick. REFERENCES: Grinenko and others, 1998. ag Agul (Rybinsk) molasse basin (Middle Devonian to Early Carboniferous) (Eastern Sayan) Consists of Middle Devonian through Early Carboniferous aerial and lacustrine sand-silt-mudstone, conglomerate, marl, and limestone with fauna and flora. Tuff, tuffite, and tuffaceous rock occur in Early Carboniferous sedimentary rocks. Ranges up to 2,000 m thick in southwestern margin of basin. Unconformably overlaps Early Devonian rocks of South Siberian volcanic-plutonic belt and Precambrian and early Paleozoic rocks of the Siberian Platform and surrounding fold belts. REFERENCES: Yanov, 1956; Graizer, Borovskaya, 1964. ags Argun sedimentary basin (Early Paleozoic) (Northeastern China) Occurs east of the Argun River in a discontinuously exposed, northeast-trending belt and consists of Cambrian and Ordovician marine, terrigenous detrital, and carbonate rocks. Cambrian units are composed of of feldspar- quartz sandstone, siltstone, shale and limestone and contain abundant Afaciacyathus sp., Bensocyathus sp., Robustocyathus yavorskii, Archaeocyathus yavorskii(Vologalin), Ethomophyllum hinganense Gu,o and other fossils. Ordovicain units consist of feldspar-quartz sandstone, siltstone, fine-grained sandstone and phylitic siltstone, and interlayered metamorphosed muddy siltstone and fine-grained sandstone with brachiopods, corals, and trilobites. Total thickness ranges up to 4,370 m. Basin unconformably overlies the Argunsky metamorphic terrane.
    [Show full text]
  • Effusive and Explosive Volcanism on the Ultraslow-Spreading Gakkel Ridge, 85E
    Article Volume 13, Number 10 6 October 2012 Q10005, doi:10.1029/2012GC004187 ISSN: 1525-2027 Effusive and explosive volcanism on the ultraslow-spreading Gakkel Ridge, 85E Claire W. Pontbriand MIT-WHOI Joint Program in Oceanography, 266 Woods Hole Road, MS 24, Woods Hole, Massachusetts 02543, USA ([email protected]) S. Adam Soule, Robert A. Sohn, Susan E. Humphris, Clayton Kunz, and Hanumant Singh Woods Hole Oceanographic Institution, 266 Woods Hole Road, MS 24, Woods Hole, Massachusetts 02543, USA ([email protected]; [email protected]; [email protected]; [email protected]; [email protected]) Ko-ichi Nakamura Institute of Geology and Geoinformation, National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba 305-8567, Japan ([email protected]) Martin Jakobsson Department of Geological Sciences, Stockholm University, SE-10691 Stockholm, Sweden ([email protected]) Timothy Shank Woods Hole Oceanographic Institution, 266 Woods Hole Road, MS 24, Woods Hole, Massachusetts 02543, USA ([email protected]) [1] We use high-definition seafloor digital imagery and multibeam bathymetric data acquired during the 2007 Arctic Gakkel Vents Expedition (AGAVE) to evaluate the volcanic characteristics of the 85E seg- ment of the ultraslow spreading Gakkel Ridge (9 mm yrÀ1 full rate). Our seafloor imagery reveals that the axial valley is covered by numerous, small-volume (order 1000 m3) lava flows displaying a range of ages and morphologies as well as unconsolidated volcaniclastic deposits with thicknesses up to 10 cm. The valley floor contains two prominent volcanic lineaments made up of axis-parallel ridges and small, cra- tered volcanic cones.
    [Show full text]
  • Quaternary Stratigraphy of the Northwind Ridge, Arctic Ocean
    Quaternary Stratigraphy of the Northwind Ridge, Arctic Ocean THESIS Presented in Partial Fulfillment of the Requirements for the Degree Master of Science in the Graduate School of The Ohio State University By Kevin Allen Crawford B.S. Graduate Program in Geological Sciences The Ohio State University 2010 Master's Examination Committee: Peter-Noel Webb, Advisor Leonid Polyak Lawrence A. Krissek Copyright by Kevin A Crawford 2010 Abstract The Arctic Ocean plays an important role in modulating the world‘s climate. Changes in sea-ice albedo and the export of freshwater into the North Atlantic could have serious repercussions to the climate patterns far beyond the Arctic. To understand fully the impacts of the retreating sea-ice cover and the warming Arctic Ocean we need to look into the past for clues. Paleoenvironments of the Arctic Ocean can be reconstructed by using sea-floor sediment constituents, such as paleobiological and mineral components as well as chemical and paleomagnetic parameters. Three cores raised from the Northwind Ridge, north of the Alaskan continental margin, were chosen to investigate sedimentary patterns and related paleoenvironments in the western Arctic Ocean across a time frame from the Holocene to estimated early Pleistocene. These cores show a range of sedimentation rates decreasing from south to north, thus allowing a development of a relatively high-resolution Upper Quaternary stratigraphy at the southern part of the ridge and a lower-resolution, yet longer stratigraphy for its northern part. In addition to this long stratigraphic coverage, the northern core has well-preserved calcareous microfauna, which provides new insights into paleoceanographic environments.
    [Show full text]
  • Drilling the Crust at Mid-Ocean Ridges
    or collective redistirbution of any portion of this article by photocopy machine, reposting, or other means is permitted only with the approval of Th e Oceanography Society. Send all correspondence to: [email protected] or Th eOceanography PO Box 1931, Rockville, USA.Society, MD 20849-1931, or e to: [email protected] Oceanography correspondence all Society. Send of Th approval portionthe ofwith any articlepermitted only photocopy by is of machine, reposting, this means or collective or other redistirbution articleis has been published in Th SPECIAL ISSUE FEATURE Oceanography Drilling the Crust Threproduction, Republication, systemmatic research. for this and teaching article copy to use in reserved. e is rights granted All OceanographyPermission Society. by 2007 eCopyright Oceanography Society. journal of Th 20, Number 1, a quarterly , Volume at Mid-Ocean Ridges An “in Depth” perspective BY BENOÎT ILDEFONSE, PETER A. RONA, AND DONNA BLACKMAN In April 1961, 13.5 m of basalts were drilled off Guadalupe In the early 1970s, almost 15 years after the fi rst Mohole Island about 240 km west of Mexico’s Baja California, to- attempt, attendees of a Penrose fi eld conference (Confer- gether with a few hundred meters of Miocene sediments, in ence Participants, 1972) formulated the concept of a layered about 3500 m of water. This fi rst-time exploit, reported by oceanic crust composed of lavas, underlain by sheeted dikes, John Steinbeck for Life magazine, aimed to be the test phase then gabbros (corresponding to the seismic layers 2A, 2B, for the considerably more ambitious Mohole project, whose and 3, respectively), which themselves overlay mantle perido- objective was to drill through the oceanic crust down to tites.
    [Show full text]
  • Discovery of a Black Smoker Vent Field and Vent Fauna at the Arctic Mid-Ocean Ridge
    ARTICLE Received 17 May 2010 | Accepted 27 Oct 2010 | Published 23 Nov 2010 DOI: 10.1038/ncomms1124 Discovery of a black smoker vent field and vent fauna at the Arctic Mid-Ocean Ridge Rolf B. Pedersen1,2, Hans Tore Rapp1,3, Ingunn H. Thorseth1,2, Marvin D. Lilley4, Fernando J.A.S. Barriga5, Tamara Baumberger6, Kristin Flesland1,2, Rita Fonseca5,7, Gretchen L. Früh-Green7 & Steffen L. Jorgensen1,3 The Arctic Mid-Ocean Ridge (AMOR) represents one of the most slow-spreading ridge systems on Earth. Previous attempts to locate hydrothermal vent fields and unravel the nature of venting, as well as the provenance of vent fauna at this northern and insular termination of the global ridge system, have been unsuccessful. Here, we report the first discovery of a black smoker vent field at the AMOR. The field is located on the crest of an axial volcanic ridge (AVR) and is associated with an unusually large hydrothermal deposit, which documents that extensive venting and long-lived hydrothermal systems exist at ultraslow-spreading ridges, despite their strongly reduced volcanic activity. The vent field hosts a distinct vent fauna that differs from the fauna to the south along the Mid-Atlantic Ridge. The novel vent fauna seems to have developed by local specialization and by migration of fauna from cold seeps and the Pacific. 1 Centre for Geobiology, University of Bergen, 5007 Bergen, Norway. 2 Department of Earth Science, University of Bergen, 5007 Bergen, Norway. 3 Department of Biology, University of Bergen, 5007 Bergen, Norway. 4 School of Oceanography, University of Washington, Seattle, 98195-7940 Washington, USA.
    [Show full text]
  • Oceanographyra Spocietyhy
    OceThe OfficiaaL MaganZineog of the Oceanographyra Spocietyhy CITATION Rubin, K.H., S.A. Soule, W.W. Chadwick Jr., D.J. Fornari, D.A. Clague, R.W. Embley, E.T. Baker, M.R. Perfit, D.W. Caress, and R.P. Dziak. 2012. Volcanic eruptions in the deep sea. Oceanography 25(1):142–157, http://dx.doi.org/10.5670/oceanog.2012.12. DOI http://dx.doi.org/10.5670/oceanog.2012.12 COPYRIGHT This article has been published inOceanography , Volume 25, Number 1, a quarterly journal of The Oceanography Society. Copyright 2012 by The Oceanography Society. All rights reserved. USAGE Permission is granted to copy this article for use in teaching and research. Republication, systematic reproduction, or collective redistribution of any portion of this article by photocopy machine, reposting, or other means is permitted only with the approval of The Oceanography Society. Send all correspondence to: [email protected] or The Oceanography Society, PO Box 1931, Rockville, MD 20849-1931, USA. downLoaded from http://www.tos.org/oceanography OCEANIC SPREADING CENTER PROCESSES | Ridge 2000 PROGRAM RESEARCH Volcanic Eruptions in the Deep Sea BY KEnnETH H. RUBIN, S. ADAM SOULE, WILLIAM W. CHADWICK JR., DANIEL J. FORNARI, DAVID A. CLAGUE, RobERT W. EMBLEY, EDWARD T. BAKER, MICHAEL R. PERFIT, DAVID W. CAREss, AND RobERT P. DZIAK Eruption of molten lapilli, ash, and sulfur-rich fumes at Hades vent, West Mata Volcano. 142 Oceanography | Vol. 25, No. 1 AbsTRACT. Volcanic eruptions are important events in Earth’s cycle of magma eruptions, we also discuss submarine generation and crustal construction. Over durations of hours to years, eruptions eruptions in other settings because produce new deposits of lava and/or fragmentary ejecta, transfer heat and magmatic volcanism is a continuum of conditions volatiles from Earth’s interior to the overlying air or seawater, and significantly and processes across the full range of modify the landscape and perturb local ecosystems.
    [Show full text]
  • Seismic Character of Volcanic Activity at the Ultraslow-Spreading Gakkel Ridge
    Seismic character of volcanic activity at the ultraslow-spreading Gakkel Ridge M. Tolstoy Lamont-Doherty Earth Observatory, 61 Route 9W, Palisades, New York 10964, USA D.R. Bohnenstiehl M.H. Edwards Hawaii Institute of Geophysics and Planetology, University of Hawaii at Manoa, 1680 East-West Road, Honolulu, Hawaii 96822, USA G.J. Kurras School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, 1680 East-West Road, Honolulu, Hawaii 96822, USA ABSTRACT area on May 6, 1999, directly following the period of intense activity Never before has a volcanic eruption on a slow- or ultraslow- and still within the period of continued lesser activity. Sidescan sonar spreading mid-ocean ridge been both observed seismically and con- images and bathymetric data show a large area (;40 km2) of unfaulted ®rmed on the sea¯oor. During the ®rst half of 1999, a long-lived ¯ows, centered in the area of intense seismic activity (Edwards et al., volcanic-spreading event occurred on the ultraslow-spreading Gak- 2001). Thus, we are presented with our ®rst opportunity to characterize kel Ridge in the Arctic Ocean. The seismicity associated with this the seismicity associated with an eruption on an ultraslow-spreading event was unprecedented in duration and magnitude for a sea¯oor ridge and consider the implications. eruption. Sonar images from the U.S.S. Hawkbill, which passed over the area within four months of the start of activity, are con- sistent with the presence of a large, recently erupted ¯ow and a ERUPTION SCALE volcanic peak directly in the area of seismic activity.
    [Show full text]
  • Gravity Evidence of Very Thin Crust at the Gakkel Ridge (Arctic Ocean)
    EPSL ELSEVIER Earth and Planetary Science Letters 162 (1998) 81±95 Gravity evidence of very thin crust at the Gakkel Ridge (Arctic Ocean) BernardJ.CoakleyŁ, James R. Cochran Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY 10964, USA Received 9 February 1998; accepted 29 June 1998 Abstract Gakkel Ridge, the active spreading center in the Arctic Ocean, is the slowest spreading portion of the global mid-ocean ridge system. Total spreading rates range from 0.6 cm=yr in the east where the ridge disappears beneath the Laptev shelf to 1.3 cm=yr in the west near Greenland. Bathymetry and gravity surveys of four sections of the Gakkel Ridge were carried out in 1996 by the U.S. Navy nuclear submarine USS POGY as part of SCICEX 96 in order to sample variations in sea¯oor morphology and gravity anomalies as a function of spreading rate. The ridge axis throughout the survey area is characterized by a continuous axial rift valley similar to that observed at other slow spreading ridges. The continuous rift axis suggests that well-organized sea¯oor spreading is occurring at total spreading rates of less than 1 cm=yr. In three faster spreading (1.13±1.24 cm=yr) western survey areas located between 7ëE and 54ëE, the Gakkel Ridge is deep compared with other ridge axes. Axial depths range between 4600 and 5100 m and ridge ¯anks at about 3200 m. The ridge ¯ank morphology is very blocky and is characterized by large scarps and deep fault-bounded troughs. Very large amplitude free-water anomalies with peak-to-trough amplitudes of 85±150 mGal are observed centered on the axis of the Gakkel Ridge.
    [Show full text]
  • An Ultraslow-Spreading Class of Ocean Ridge
    articles An ultraslow-spreading class of ocean ridge Henry J. B. Dick, Jian Lin & Hans Schouten Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, USA ........................................................................................................................................................................................................................... New investigations of the Southwest Indian and Arctic ridges reveal an ultraslow-spreading class of ocean ridge that is characterized by intermittent volcanism and a lack of transform faults. We find that the mantle beneath such ridges is emplaced continuously to the seafloor over large regions. The differences between ultraslow- and slow-spreading ridges are as great as those between slow- and fast-spreading ridges. The ultraslow-spreading ridges usually form at full spreading rates less than about 12 mm yr21, though their characteristics are commonly found at rates up to approximately 20 mm yr21. The ultraslow-spreading ridges consist of linked magmatic and amagmatic accretionary ridge segments. The amagmatic segments are a previously unrecognized class of accretionary plate boundary structure and can assume any orientation, with angles relative to the spreading direction ranging from orthogonal to acute. These amagmatic segments sometimes coexist with magmatic ridge segments for millions of years to form stable plate boundaries, or may displace or be displaced by transforms and magmatic ridge segments as spreading rate, mantle thermal structure and ridge
    [Show full text]
  • Constraints from Alkaline Volcanism in the Chersky Belt (Yakutia)
    Lithos 125 (2011) 825–835 Contents lists available at ScienceDirect Lithos journal homepage: www.elsevier.com/locate/lithos Magmatism at the Eurasian–North American modern plate boundary: Constraints from alkaline volcanism in the Chersky Belt (Yakutia) Cornelius Tschegg a,⁎, Michael Bizimis b, David Schneider c, Vyacheslav V. Akinin d, Theodoros Ntaflos a a Department of Lithospheric Research, University of Vienna, Vienna, Austria b Department of Earth and Ocean Sciences, University of South Carolina, Columbia, SC, United States c Department of Earth Sciences, University of Ottawa, Ottawa, Canada d North East Interdisciplinary Scientific Research Institute, Russian Academy of Science, Magadan, Russia article info abstract Article history: The Chersky seismic belt (NE-Russia) forms the modern plate boundary of the Eurasian−North American Received 3 March 2011 continental plate. The geodynamic evolution of this continent−continent setting is highly complex and remains a Accepted 30 April 2011 matter of debate, as the extent and influence of the Mid-Arctic Ocean spreading center on the North Asian Available online 7 May 2011 continent since the Eocene remains unclear. The progression from a tensional stress regime to a modern day transpressional one in the Chersky seismic belt, makes the understanding even more complicated. The alkaline Keywords: volcanism that has erupted along the Chersky range from Eocene through to the Recent can provide constraints Alkaline volcanism Chersky seismic belt on the geodynamic evolution of this continental boundary, however, the source and petrogenetic evolution of Eurasian–North American plate boundary these volcanic rocks and their initiating mechanisms are poorly understood. Arctic Ocean spreading We studied basanites of the central Chersky belt, which are thought to represent the first alkaline volcanic Asthenospheric adiabatic decompression activity in the area, after initial opening of the Arctic Ocean basin.
    [Show full text]
  • Earth's Complex Complexion
    http://oceanusmag.whoi.edu/v42n2/dick.html Earth’s Complex Complexion Expeditions to remote oceans expose new variations in ocean crust By Henry J.B. Dick, Senior Scientist, The creation and cooling of oceanic gold and silver. So how Earth’s crust forms Geology and Geophysics Department, crust is the primary means by which heat is more than just an academic question. Woods Hole Oceanographic Institution escapes from Earth’s interior. In this dy- namic planet-scale crucible, heat, chemi- The seafloor layer cake ven as you read this, Earth’s crust is cals and minerals are transported from Several generations of scientists have Econtinually being reborn and recycled Earth’s interior to its surface. dredged rock samples from the seafloor, in a dynamic process that fundamentally Over the long haul, the process ulti- employed submarines and robots to study shapes our planet. We’re not generally mately determines Earth’s chemical make- it, and even drilled into it to learn a aware of all this action because most of it up. It affects the amount of carbon dioxide considerable amount about the shallow occurs at the seafloor, under a formidable and water in the crust, oceans, and atmo- oceanic crust. We’ve analyzed seismic watery shroud, and often in remote re- sphere, and it produces zinc, copper, and waves that penetrate and reflect off rock gions of the oceans. other mineral deposits, including some layers deep in the crust in an effort to Working in the ice-covered Arctic Ocean in 2001, scientists and crew aboard the maiden voyage of the U.S.
    [Show full text]
  • Plate Boundaries in the Far East Region of Russia (From GPS Measurement, Seismic- Prospecting, and Seismological Data)
    See discussions, stats, and author profiles for this publication at: https://www.researchgate.net/publication/257480457 Plate boundaries in the Far East region of Russia (from GPS measurement, seismic- prospecting, and seismological data) Article in Russian Geology and Geophysics · April 2012 DOI: 10.1016/j.rgg.2012.03.002 CITATIONS READS 5 258 9 authors, including: D. G. Ardyukov Nikolay V. Shestakov A.A. Trofimuk Institute of Petroleum Geology … Far Eastern Federal University 23 PUBLICATIONS 87 CITATIONS 30 PUBLICATIONS 100 CITATIONS SEE PROFILE SEE PROFILE A.V. Timofeev A.A. Trofimuk Institute of Petroleum Geology … 9 PUBLICATIONS 28 CITATIONS SEE PROFILE Some of the authors of this publication are also working on these related projects: Ionospheric effects of meteorite falls View project All content following this page was uploaded by Nikolay V. Shestakov on 02 December 2014. The user has requested enhancement of the downloaded file. All in-text references underlined in blue are added to the original document and are linked to publications on ResearchGate, letting you access and read them immediately. Available online at www.sciencedirect.com Russian Geology and Geophysics 53 (2012) 376–391 www.elsevier.com/locate/rgg Plate boundaries in the Far East region of Russia (from GPS measurement, seismic-prospecting, and seismological data) V.Yu. Timofeev a,*, D.G. Ardyukov a, V.M. Solov’ev b, S.V. Shibaev c, A.F. Petrov c, P.Yu. Gornov d, N.V. Shestakov e,f, E.V. Boiko a, A.V. Timofeev a a A.A. Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences, pr.
    [Show full text]