DOCSLIB.ORG

Rapid Microplate Rotations and Backarc Rifting at the Transition Between Collision and Subduction

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Rapid Microplate Rotations and Backarc Rifting at the Transition Between Collision and Subduction Rapid microplate rotations and backarc rifting at the transition between collision and subduction Laura M. Wallace Institute of Geological and Nuclear Science, Lower Hutt 6315, New Zealand Robert McCaffrey Department of Earth and Environmental Science, Rensselaer Polytechnic Institute, 110 8th Street, Troy, New York 12180, USA John Beavan Institute of Geological and Nuclear Science, Lower Hutt 6315, New Zealand Susan Ellis ABSTRACT In all regions studied, we de®ne the geometry Using global positioning system velocities from convergent plate boundaries in Papua of block boundaries (faults) based on earth- New Guinea, New Zealand, Tonga, Vanuatu, and the Marianas, we note a spatial corre- quakes and geology. To place the regional lation between rapid tectonic block rotations and the transition from subduction to col- GPS velocities into larger plate kinematic con- lision. We present a mechanism for the block rotations, in which the change from collision texts, we use GPS velocities from sites on the of a buoyant indentor to normal subduction exerts a torque on the upper-plate microplate. bounding plates (e.g., Australian, Paci®c, and This work improves our understanding of the causes of rapid vertical axis rotations, often Philippine Sea plates) given in Beavan et al. observed in paleomagnetic studies. We also show how collision-induced rotations may lead (2002) and Sella et al. (2002). to backarc rifting. Papua New Guinea Keywords: GPS, global positioning system, collision, subduction, microplate rotation, backarc Papua New Guinea forms the boundary rifting, tectonics. zone between the obliquely and rapidly (;110 mm/yr) converging Australian and Paci®c INTRODUCTION the interseismic period are hampered by the plates (Fig. 1). The southern boundary of the The fastest modern-day tectonic block ro- effects of elastic strain due to locking on faults South Bismarck microplate changes (from tations, as much as 98/m.y., occur in the fore- (particularly the subduction zone). To deal west to east) from collision between the Fin- arcs of convergent plate margins (e.g., Cal- with this problem, we simultaneously invert isterre Range and the underthrusting New mant et al., 2003; Wallace et al., 2004a). It GPS velocities, earthquake slip vector azi- Guinea Highlands to subduction of oceanic has been suggested that the bending and ro- muths, transform fault orientations, and long- crust at the New Britain trench in the Solomon tation of subduction-zone forearcs can be term geological fault slip rates (including sea- Sea. The northern boundary of the South Bis- caused by collision of buoyant features with ¯oor spreading rates) for angular velocities of marck microplate is marked by the Manus and the subduction zone (e.g., Vogt et al., 1976; tectonic blocks and the degree of coupling on New Guinea backarc rifts, which are connect- McCabe, 1984). Earlier studies of forearc faults bounding the blocks (e.g., McCaffrey, ed by left-lateral transform faults along the block rotations were based on paleomagnetic 1995, 2002). Throughout this paper we refer Bismarck Sea seismic lineation (e.g., Taylor, declination anomalies that can provide the to the point where the angular velocity inter- 1979). GPS velocities (Wallace et al., 2004a) long-term vertical axis rotation rate, but can- sects Earth's surface as the ``pole of rotation.'' show that the South Bismarck microplate ro- not constrain the full angular velocity, so that We refer to the tectonic blocks or microplates tates clockwise relative to the New Guinea the orientation of the spin axis is unknown. (often coinciding with the forearc and/or arc) Highlands microplate (the lower plate of the Using published global positioning system as ``convergent plate boundary microblocks.'' collision) at ;98/m.y. about a pole where the (GPS) velocities from ®ve convergent margins around the world, we estimate the angular ve- locities of forearc blocks to reveal an apparent Figure 1. Tectonic setting spatial relationship between the rotation of up- of Papua New Guinea and per-plate microplates and the collisions of vectors showing rotation buoyant crustal masses (e.g., oceanic plateaus, of South Bismarck plate seamount chains, or continental fragments) (SBS) relative to lower plate (see Wallace et al., with the subduction zones. We suggest that the 2004a, for details of mod- change from collision to subduction exerts a eling results). Pole of ro- torque on the upper-plate microplate, causing tation for South Bismarck the microplate to rotate rapidly (relative to the microplate relative to New Guinea Highlands subducting plate) about a point near where the (NGH) is shown by semi- collision occurs. These rotations often result circular arrow, clockwise. in backarc rifting. Our observations have im- Rates of rifting in Manus plications for the knowledge of what drives Basin (white arrows) are rapid crustal block rotations, and the causes of given in mm/yr. BSSLÐ Bismarck Sea seismic lin- backarc rifting. eation. In best-®tting x2 5 model, we obtain n KINEMATIC MODELING OF BLOCK 1.99, using 333 earth- ROTATIONS AT CONVERGENT quake slip vectors and 66 PLATE BOUNDARIES global positioning sys- tem velocities to estimate Estimates of tectonic block rotations at sub- 44 parameters. duction margins from GPS velocities during q 2005 Geological Society of America. For permission to copy, contact Copyright Permissions, GSA, or [email protected]. Geology; November 2005; v. 33; no. 11; p. 857±860; doi: 10.1130/G21834.1; 5 ®gures. 857 Figure 3. Tectonic setting of Tonga (Tong) and Va- nuatu (Van), global posi- tioning system (GPS) ve- locities (observed, black; model, red), and rotation poles of Vanuatu and Tonga tectonic blocks rel- ative to subducting plate. GPS velocity vectors shown relative to Austra- lian (Aus) plate. White vectors with rates next to them show relative mo- tion in backarc (rates are in mm/yr, predicted from block model). For best x2 5 model, we obtain n 2.13, using 952 earth- quake slip vectors, 4 spreading rates, and 83 GPS velocities to esti- mate 42 free parameters. NHTÐNew Hebrides Trench; EFTÐErromango-Futuna Trough; WTPÐWest Torres Plateau; DERÐD'Entrecasteaux Ridge; VANÐVanuatu; WNFBÐwestern North Fiji Basin; HHRÐHazel Holme Ridge; CSRÐcentral spreading ridge. velocities show that several crustal blocks in wise rotation rate of Tonga estimated from pa- the eastern North Island rotate clockwise at leomagnetic studies (Sager et al., 1994). 3.88±5.08/m.y. relative to the subducting Pa- ci®c plate (Wallace et al., 2004b). Paleomag- Vanuatu Figure 2. Rotation of New Zealand tectonic netic declinations and geological strain esti- Vanuatu straddles the Australia±Paci®c blocks relative to Paci®c plate and tectonic mates also suggest clockwise rotation of the plate boundary zone between the Tonga-Fiji setting (see Wallace et al., 2004b, for details eastern North Island (e.g., Walcott, 1984; region and New Guinea (Fig. 3). The major of modeling results). Tectonic blocks and Beanland and Haines, 1998). Backarc rifting tectonic features in this region are the New their respective poles of rotation are labeled (block names: WAIRÐWairarapa, RAUKÐ in the Taupo volcanic zone (central North Is- Hebrides Trench, where Australia subducts be- Raukumara, CHKGÐCentral Hikurangi, land) is related to eastern North Island rota- neath Vanuatu, and a complex series of rifts AXIRÐAxial Ranges). White vectors are la- tion. The poles of rotation of the eastern North and transforms in the North Fiji Basin. Sub- beled with extension rates in Taupo volcanic Island tectonic blocks relative to the subduct- duction of various buoyant features at the New zone (TVZ) and convergence rates at Hiku- ing Paci®c plate are located adjacent to where Hebrides Trench (e.g., D'Entrecasteaux Ridge; rangi Trough (rates in mm/yr). Note: arrows in TVZ are not to scale. In our best-®tting the buoyant Chatham Rise impinges upon the West Torres Plateau) has in¯uenced the recent x2 5 model, we obtain n 1.32 from 367 GPS margin (Fig. 2). deformation of the Vanuatu island chain (e.g., velocities, 10 earthquake slip vectors, and Pelletier et al., 1998; Calmant et al., 2003). 138 free parameters. Tonga Schellart et al. (2002) suggested that the North The Paci®c plate subducts westward be- Fiji Basin is produced by asymmetric opening Finisterre collision is most advanced (Fig. 1). neath the Australian plate (Fig. 3) at the Tonga about a hinge point located near 118S, 1658E, South Bismarck microplate rotation results in Trench east of the Tonga Islands. West of Ton- and that this asymmetric opening is produced rapid rifting in the Manus and New Guinea ga, some of the highest documented rates of by variation in the degree of rollback of the Basins. Paleomagnetic evidence indicates that backarc rifting in the world are in the Lau Ba- subducting Australian plate. the South Bismarck microplate has been ro- sin (e.g., Bevis et al., 1995; Taylor et al., Following Calmant et al. (2003), we divide tating clockwise at an average rate of 88/m.y. 1996). The southern limit of rifting in the Lau Vanuatu into central and southern tectonic since the Finisterre collision initiated (Weiler Basin is near 268S, adjacent to where the Lou- blocks and include the western North Fiji Ba- and Coe, 2000), consistent with the geodetic isville Seamount chain subducts, and rifting sin as a separate block (Fig. 3). The eastern rates. propagates south at ;100 mm/yr (Parson and boundaries of the southern and central blocks Wright, 1996; Taylor et al., 1996) (Fig. 3). coincide with the zone of backarc thrusting New Zealand Much of the rifting history of the eastern Lau and extension just to the east of the island The plate boundary in the North Island, Basin is linked to the 128 mm/yr southward chain. We invert GPS velocities (Calmant et New Zealand, accommodates subduction of migration of the Louisville Seamount chain± al., 2003), spreading rates (Pelletier et al., the Paci®c plate beneath the North Island at Tonga Trench intersection (Pelletier et al., 1998), and earthquake slip vectors for angular the Hikurangi Trough (Fig.
Load more

Recommended publications
  • 0 Master's Thesis the Department of Geosciences And
    Master’s thesis The Department of Geosciences and Geography Physical Geography South American subduction zone processes: Visualizing the spatial relation of earthquakes and volcanism at the subduction zone Nelli Metiäinen May 2019 Thesis instructors: David Whipp Janne Soininen HELSINGIN YLIOPISTO MATEMAATTIS-LUONNONTIETEELLINEN TIEDEKUNTA GEOTIETEIDEN JA MAANTIETEEN LAITOS MAANTIEDE PL 64 (Gustaf Hällströmin katu 2) 00014 Helsingin yliopisto 0 Tiedekunta/Osasto – Fakultet/Sektion – Faculty Laitos – Institution – Department Faculty of Science The Department of Geosciences and Geography Tekijä – Författare – Author Nelli Metiäinen Työn nimi – Arbetets titel – Title South American subduction zone processes: Visualizing the spatial relation of earthquakes and volcanism at the subduction zone Oppiaine – Läroämne – Subject Physical Geography Työn laji – Arbetets art – Level Aika – Datum – Month and year Sivumäärä – Sidoantal – Number of pages Master’s thesis May 2019 82 + appencides Tiivistelmä – Referat – Abstract The South American subduction zone is the best example of an ocean-continent convergent plate margin. It is divided into segments that display different styles of subduction, varying from normal subduction to flat-slab subduction. This difference also effects the distribution of active volcanism. Visualizations are a fast way of transferring large amounts of information to an audience, often in an interest-provoking and easily understandable form. Sharing information as visualizations on the internet and on social media plays a significant role in the transfer of information in modern society. That is why in this study the focus is on producing visualizations of the South American subduction zone and the seismic events and volcanic activities occurring there. By examining the South American subduction zone it may be possible to get new insights about subduction zone processes.
    [Show full text]
  • Dynamic Subsidence of Eastern Australia During the Cretaceous
    Gondwana Research 19 (2011) 372–383 Contents lists available at ScienceDirect Gondwana Research journal homepage: www.elsevier.com/locate/gr Dynamic subsidence of Eastern Australia during the Cretaceous Kara J. Matthews a,⁎, Alina J. Hale a, Michael Gurnis b, R. Dietmar Müller a, Lydia DiCaprio a,c a EarthByte Group, School of Geosciences, The University of Sydney, NSW 2006, Australia b Seismological Laboratory, California Institute of Technology, Pasadena, CA 91125, USA c Now at: ExxonMobil Exploration Company, Houston, TX, USA article info abstract Article history: During the Early Cretaceous Australia's eastward passage over sinking subducted slabs induced widespread Received 16 February 2010 dynamic subsidence and formation of a large epeiric sea in the eastern interior. Despite evidence for Received in revised form 25 June 2010 convergence between Australia and the paleo-Pacific, the subduction zone location has been poorly Accepted 28 June 2010 constrained. Using coupled plate tectonic–mantle convection models, we test two end-member scenarios, Available online 13 July 2010 one with subduction directly east of Australia's reconstructed continental margin, and a second with subduction translated ~1000 km east, implying the existence of a back-arc basin. Our models incorporate a Keywords: Geodynamic modelling rheological model for the mantle and lithosphere, plate motions since 140 Ma and evolving plate boundaries. Subduction While mantle rheology affects the magnitude of surface vertical motions, timing of uplift and subsidence Australia depends on plate boundary geometries and kinematics. Computations with a proximal subduction zone Cretaceous result in accelerated basin subsidence occurring 20 Myr too early compared with tectonic subsidence Tectonic subsidence calculated from well data.
    [Show full text]
  • Co-Simulation Redondante D'échelles De Modélisation
    THÈSE / UNIVERSITÉ DE BRETAGNE OCCIDENTALE présentée par sous le sceau de l’Université Bretagne Loire Sébastien Le Yaouanq pour obtenir le titre de DOCTEUR DE L’UNIVERSITÉ DE BRETAGNE OCCIDENTALE préparée au Centre Européen de Réalité Virtuelle, Mention : Informatique Laboratoire CNRS Lab-STICC École Doctorale SICMA ! Thèse soutenue le 17 juin 2016 Co-simulation redondante d’échelles de devant le jury composé de : Samir Otmane (Rapporteur) modélisation hétérogènes pour une Professeur, Université d’Evry Val d’Essonne Éric Ramat (Rapporteur) approche phénoménologique. Professeur, Université du Littoral Côte d’Opale Vincent Chevrier (Examinateur) Professeur, Université de Lorraine Jacques Tisseau (Directeur de thèse) Professeur, ENI Brest Pascal Redou (Encadrant) Maître de Conférence, HDR, ENI Brest Christophe Le Gal (Encadrant) Directeur général, Docteur, CERVVAL Université Bretagne Loire — Mémoire de thèse — Spécialité : Informatique Co-simulation redondante d’échelles de modélisation hétérogènes pour une approche phénoménologique Sébastien Le Yaouanq Soutenue le 17 juin 2016 devant la commission d’examen : Rapporteurs Samir Otmane Professeur, Université d’Evry Val d’Essone Eric Ramat Professeur, Université du Littoral Côte d’Opale Examinateurs Vincent Chevrier Professeur, Université de Lorraine Pascal Redou Maître de conférences, HDR, ENI Brest Christophe Le Gal Directeur général, Docteur, CERVVAL Directeur Jacques Tisseau Professeur, ENI Brest Co-simulation redondante d’échelles de modélisation hétérogènes pour une approche phénoménologique
    [Show full text]
  • Environmental Geology Chapter 2 -‐ Plate Tectonics and Earth's Internal
    Environmental Geology Chapter 2 - Plate Tectonics and Earth’s Internal Structure • Earth’s internal structure - Earth’s layers are defined in two ways. 1. Layers defined By composition and density o Crust-Less dense rocks, similar to granite o Mantle-More dense rocks, similar to peridotite o Core-Very dense-mostly iron & nickel 2. Layers defined By physical properties (solid or liquid / weak or strong) o Lithosphere – (solid crust & upper rigid mantle) o Asthenosphere – “gooey”&hot - upper mantle o Mesosphere-solid & hotter-flows slowly over millions of years o Outer Core – a hot liquid-circulating o Inner Core – a solid-hottest of all-under great pressure • There are 2 types of crust ü Continental – typically thicker and less dense (aBout 2.8 g/cm3) ü Oceanic – typically thinner and denser (aBout 2.9 g/cm3) The Moho is a discontinuity that separates lighter crustal rocks from denser mantle below • How do we know the Earth is layered? That knowledge comes primarily through the study of seismology: Study of earthquakes and seismic waves. We look at the paths and speeds of seismic waves. Earth’s interior boundaries are defined by sudden changes in the speed of seismic waves. And, certain types of waves will not go through liquids (e.g. outer core). • The face of Earth - What we see (Observations) Earth’s surface consists of continents and oceans, including mountain belts and “stable” interiors of continents. Beneath the ocean, there are continental shelfs & slopes, deep sea basins, seamounts, deep trenches and high mountain ridges. We also know that Earth is dynamic and earthquakes and volcanoes are concentrated in certain zones.
    [Show full text]
  • Plate Tectonics
    Plate tectonics tive motion determines the type of boundary; convergent, divergent, or transform. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along these plate boundaries. The lateral relative move- ment of the plates typically varies from zero to 100 mm annually.[2] Tectonic plates are composed of oceanic lithosphere and thicker continental lithosphere, each topped by its own kind of crust. Along convergent boundaries, subduction carries plates into the mantle; the material lost is roughly balanced by the formation of new (oceanic) crust along divergent margins by seafloor spreading. In this way, the total surface of the globe remains the same. This predic- The tectonic plates of the world were mapped in the second half of the 20th century. tion of plate tectonics is also referred to as the conveyor belt principle. Earlier theories (that still have some sup- porters) propose gradual shrinking (contraction) or grad- ual expansion of the globe.[3] Tectonic plates are able to move because the Earth’s lithosphere has greater strength than the underlying asthenosphere. Lateral density variations in the mantle result in convection. Plate movement is thought to be driven by a combination of the motion of the seafloor away from the spreading ridge (due to variations in topog- raphy and density of the crust, which result in differences in gravitational forces) and drag, with downward suction, at the subduction zones. Another explanation lies in the different forces generated by the rotation of the globe and the tidal forces of the Sun and Moon. The relative im- portance of each of these factors and their relationship to each other is unclear, and still the subject of much debate.
    [Show full text]
  • A Tracer-Based Algorithm for Automatic Generation of Seafloor
    A Tracer-Based Algorithm for Automatic Generation of Seafloor Age Grids from Plate Tectonic Reconstructions Krister S. Karlsen ([email protected]), Mathew Domeier, Carmen Gaina and Clinton P. Conrad Centre for Earth Evolution and Dynamics, University of Oslo, Norway Abstract The age of the ocean floor and its time-dependent age distribution control funda- mental features of the Earth, such as bathymetry, sea level and mantle heat loss. Recently, the development of increasingly sophisticated reconstructions of past plate motions has provided models for plate kinematics and plate boundary evolution back in geological time. These models implicitly include the information necessary to de- termine the age of ocean floor that has since been lost to subduction. However, due to the lack of an automated and efficient method for generating global seafloor age grids, many tectonic models, most notably those extending back into the Paleozoic, are published without an accompanying set of age models for oceanic lithosphere. Here we present an automatic, tracer-based algorithm that generates seafloor age grids from global plate tectonic reconstructions with defined plate boundaries. Our method enables us to produce the first seafloor age models for the Paleozoic’s lost ocean basins. Estimated changes in sea level based on bathymetry inferred from our new age grids show good agreement with sea level record estimations from proxies, providing a possible explanation for the peak in sea level during the assembly phase of Pangea. This demonstrates how our seafloor age models can be directly compared with observables from the geologic record that extend further back in time than the constraints from preserved seafloor.
    [Show full text]
  • The Temporal Evolution of Plate Driving Forces: Importance of Slab Suction
    JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 109, B10407, doi:10.1029/2004JB002991, 2004 The temporal evolution of plate driving forces: Importance of ‘‘slab suction’’ versus ‘‘slab pull’’ during the Cenozoic Clinton P. Conrad and Carolina Lithgow-Bertelloni Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan, USA Received 23 January 2004; revised 27 June 2004; accepted 30 July 2004; published 16 October 2004. [1] Although mantle slabs ultimately drive plate motions, the mechanism by which they do so remains unclear. A detached slab descending through the mantle will excite mantle flow that exerts shear tractions on the base of the surface plates. This ‘‘slab suction’’ force drives subducting and overriding plates symmetrically toward subduction zones. Alternatively, cold, strong slabs may effectively transmit stresses to subducting surface plates, exerting a direct ‘‘slab pull’’ force on these plates, drawing them rapidly toward subduction zones. This motion induces mantle flow that pushes overriding plates away from subduction zones. We constrain the relative importance of slab suction and slab pull by comparing Cenozoic plate motions to model predictions that include viscous mantle flow and a proxy for slab strength. We find that slab pull from upper mantle slabs combined with slab suction from lower mantle slabs explains the observation that subducting plates currently move 4 times faster than nonsubducting plates. This implies that upper mantle slabs are strong enough to support their own weight. Slab suction and slab pull presently account for about 40 and 60% of the forces on plates, but slab suction only 30% if a low-viscosity asthenosphere decouples plates from mantle flow.
    [Show full text]
  • On the Role of Slab Pull in the Cenozoic Motion of the Pacific Plate Claudio Faccenna, Thorsten W
    On the role of slab pull in the Cenozoic motion of the Pacific plate Claudio Faccenna, Thorsten W. Becker, Serge Lallemand, Bernhard Steinberger To cite this version: Claudio Faccenna, Thorsten W. Becker, Serge Lallemand, Bernhard Steinberger. On the role of slab pull in the Cenozoic motion of the Pacific plate. Geophysical Research Letters, American Geophysical Union, 2012, 39, pp.L03305. 10.1029/2011GL050155. hal-00682150 HAL Id: hal-00682150 https://hal.archives-ouvertes.fr/hal-00682150 Submitted on 25 Jan 2016 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. GEOPHYSICAL RESEARCH LETTERS, VOL. 39, L03305, doi:10.1029/2011GL050155, 2012 On the role of slab pull in the Cenozoic motion of the Pacific plate Claudio Faccenna,1,2 Thorsten W. Becker,3 Serge Lallemand,4 and Bernhard Steinberger5,6 Received 27 October 2011; revised 29 December 2011; accepted 3 January 2012; published 8 February 2012. [1] We analyze the role of slab pull acting on the Pacific plate using plate reconstructions [e.g., Lithgow-Bertelloni and plate during its early Tertiary change in motion. Slab pull Richards, 1998; Conrad and Lithgow-Bertelloni, 2002, 2004]. forces are estimated by integrating the negative buoyancy [3] The Pacific plate represents a key site to analyze of a 700 km long slab along a revised subduction boundary the different force contributions as it is the fastest plate on model adopting the Müller et al.
    [Show full text]
  • RESEARCH Ridge-Push Force and the State of Stress
    RESEARCH Ridge-push force and the state of stress in the Nubia- Somalia plate system Rezene Mahatsente1 and David Coblentz2 1DEPARTMENT OF GEOLOGICAL SCIENCES, UNIVERSITY OF ALABAMA, TUSCALOOSA, ALABAMA 35487, USA 2EARTH AND ENVIRONMENTAL SCIENCES DIVISION, LOS ALAMOS NATIONAL LABORATORY, LOS ALAMOS, NEW MEXICO 87545, USA ABSTRACT We assessed the relative contribution of ridge-push forces to the stress state of the Nubia-Somalia plate system by comparing ridge-push forces with lithospheric strength in the oceanic part of the plate, based on estimates from plate cooling and rheological models. The ridge- push forces were derived from the thermal state of the oceanic lithosphere, seafloor depth, and crustal age data. The results of the compari- son show that the magnitude of the ridge-push forces is less than the integrated strength of the oceanic part of the plate. This implies that the oceanic part of the plate is very little deformed; thus, the ridge-push forces may be compensated by significant strain rates outside the oceanic parts of the plate. We used an elastic finite element analysis of geoid gradients of the upper mantle to evaluate stresses associated with the gravitational potential energy of the surrounding ridges and show that these stresses may be transmitted through the oceanic part of the plate, with little modulation in magnitude, before reaching the continental regions. We therefore conclude that the present-day stress fields in continental Africa can be viewed as the product of the gravitational potential energy of the ridge ensemble surrounding the plate in conjunction with lateral variations in lithospheric structure within the continent regions.
    [Show full text]
  • On the Dynamics of Plate Tectonics: Multiple Solutions, the Influence of Water, and Thermal Evolution
    On the Dynamics of Plate Tectonics: Multiple Solutions, the Influence of Water, and Thermal Evolution The Harvard community has made this article openly available. Please share how this access benefits you. Your story matters Citation Crowley, John. 2012. On the Dynamics of Plate Tectonics: Multiple Solutions, the Influence of Water, and Thermal Evolution. Doctoral dissertation, Harvard University. Citable link http://nrs.harvard.edu/urn-3:HUL.InstRepos:9385631 Terms of Use This article was downloaded from Harvard University’s DASH repository, and is made available under the terms and conditions applicable to Other Posted Material, as set forth at http:// nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of- use#LAA c 2012 John W. Crowley ! All rights reserved. Dissertation Advisor: Professor Richard J. O’Connell John W. Crowley On the Dynamics of Plate Tectonics: Multiple Solutions, the Influence of Water, and Thermal Evolution Abstract An analytic boundary layer model for thermal convection with a finite-strength plate and depth-dependent viscosity is developed. The model includes a specific energy balance for the lithosphere and accounts for coupling between the plate and underlying mantle. Mul- tiple solutions are possible with three solution branches representing three distinct modes of thermal convection. One branch corresponds to the classic boundary layer solution for active lid plate tectonics while two new branches represent solutions for sluggish lid convec- tion. The model is compared to numerical simulations with highly temperature dependent viscosity and is able to predict both the type of convection (active, sluggish, or stagnant lid) as well as the presence of single and multiple solution regimes.
    [Show full text]
  • Étude Des Mécanismes De Refroidissement Du Manteau Terrestre Simulés Par Des Systèmes Multi-Agents Manuel Combes
    Étude des mécanismes de refroidissement du manteau terrestre simulés par des systèmes multi-agents Manuel Combes To cite this version: Manuel Combes. Étude des mécanismes de refroidissement du manteau terrestre simulés par des systèmes multi-agents. Géophysique [physics.geo-ph]. Université de Bretagne occidentale - Brest, 2011. Français. tel-00874975 HAL Id: tel-00874975 https://tel.archives-ouvertes.fr/tel-00874975 Submitted on 20 Oct 2013 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. Universite´ Europeenne´ de Bretagne — M´emoire de th`ese — Sp´ecialit´e: Physique Etude´ des m´ecanismes de refroidissement du manteau terrestre simul´es par des syst`emes multi-agents Manuel Combes Soutenue le 10 novembre 2011 devant la commission d’examen : Rapporteurs Ga¨el Choblet Charg´ede Recherche `al’Universit´ede Nantes St´ephane Labrosse Professeur `al’ENS de Lyon Examinateurs Claude Jaupart Professeur `al’Institut de Physique du Globe Marc Parenthoen¨ Maitre de Conf´erences `al’ENI de Brest Yanick Ricard Directeur de Recherche `al’Universit´ede Lyon 1
    [Show full text]
  • Farallon Plate Subduction and the Laramide Orogeny by Sibiao
    Flattening the slab: Farallon plate subduction and the Laramide orogeny by Sibiao Liu A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science in Geophysics Department of Physics University of Alberta © Sibiao Liu, 2014 ii Abstract The Laramide orogeny (~80-50 Ma) was an anomalous period of mountain-building in the western United States that took place >1000 km inboard of the Farallon Plate subduction margin. The orogeny was preceded by the development of the Western Interior Seaway and eastward migration of the volcanic arc. Thus, it is believed that this marked a time of flat (subhorizontal) subduction. However, the factors that caused the Farallon Plate geometry to evolve from a steep geometry to flat subduction are not well- understood. Three mechanisms have been proposed: (1) a westward (trenchward) increase in North America plate motion, (2) an increased slab suction force owing to the presence of thick Colorado Plateau lithosphere, and (3) subduction of a buoyant oceanic plateau. This study uses 2D upper-mantle-scale numerical models to investigate these mechanisms. The models show that trenchward continental motion provides the primary control on subduction geometry, with decreasing slab dip as velocity increases. However, this can only create low-angle subduction, as the Farallon Plate was old (>100 Ma) and therefore much denser than the mantle. A transition to flat subduction requires: (1) subduction of a buoyant oceanic plateau which does not undergo eclogitization, and (2) a slab break-off at the landward side of the plateau. The break-off removes the dense frontal slab, and flat subduction develops as the oceanic plateau pulls the slab upward to a subhorizontal trajectory.
    [Show full text]