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Ocean Trench
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 Ocean trench Ocean trenches are long, narrow depressions on the seafloor. These chasms are the deepest parts of the ocean—and some of the deepest natural spots on Earth. G R A D E S 5 - 12+ S U B J E C T S Earth Science, Geology, Geography, Physical Geography C O N T E N T S 11 Images, 1 Video, 2 Links For the complete encyclopedic entry with media resources, visit: http://www.nationalgeographic.org/encyclopedia/ocean-trench/ Ocean trenches are long, narrow depressions on the seafloor. These chasms are the deepest parts of the ocean—and some of the deepest natural spots on Earth. Ocean trenches are found in every ocean basin on the planet, although the deepest ocean trenches ring the Pacific as part of the so-called “Ring of Fire” that also includes active volcanoes and earthquake zones. Ocean trenches are a result of tectonic activity, which describes the movement of the Earth’s lithosphere. In particular, ocean trenches are a feature of convergent plate boundaries, where two or more tectonic plates meet. At many convergent plate boundaries, dense lithosphere melts or slides beneath less-dense lithosphere in a process called subduction, creating a trench. Ocean trenches occupy the deepest layer of the ocean, the hadalpelagic zone. The intense pressure, lack of sunlight, and frigid temperatures of the hadalpelagic zone make ocean trenches some of the most unique habitats on Earth. -
Mantle and Geological Evidence for a Late Jurassic–Cretaceous Suture
Mantle and geological evidence for a Late Jurassic–Cretaceous suture spanning North America Mantle and geological evidence for a Late Jurassic–Cretaceous suture spanning North America Karin Sigloch1,† and Mitchell G. Mihalynuk2 1Department of Earth Sciences, University of Oxford, South Parks Road, Oxford OX1 3AN, UK 2British Columbia Geological Survey, P.O. Box Stn Prov Govt, Victoria, BC, V8W 9N3, Canada ABSTRACT of the archipelago, whereas North America ambient mantle, and seismic waves propagate converged on the archipelago by westward through it at slightly faster velocities. Joint sam- Crustal blocks accreted to North America subduction of an intervening, major ocean, pling of the subsurface by thousands to millions form two major belts that are separated by the Mezcalera-Angayucham Ocean. of crossing wave paths, generated by hundreds a tract of collapsed Jurassic–Cretaceous The most conspicuous geologic prediction or thousands of earthquakes, enables computa- basins extending from Alaska to Mexico. is that of an oceanic suture that must run tion of three-dimensional (3-D) tomographic Evidence of oceanic lithosphere that once along the entire western margin of North images of the whole-mantle structure. Some underlay these basins is rare at Earth’s sur- America. It formed diachronously between high-velocity domains connect upward to active face. Most of the lithosphere was subducted, ca. 155 Ma and ca. 50 Ma, analogous to subduction zones, providing a direct verification which accounts for the general difficulty of diachro nous suturing of southwest Pacific arcs of slab origin as cold, dense, and seismically fast reconstructing oceanic regions from sur- to the northward-migrating Australian conti- oceanic lithosphere (e.g., for North America, face evidence. -
Two Contrasting Phanerozoic Orogenic Systems Revealed by Hafnium Isotope Data William J
ARTICLES PUBLISHED ONLINE: 17 APRIL 2011 | DOI: 10.1038/NGEO1127 Two contrasting Phanerozoic orogenic systems revealed by hafnium isotope data William J. Collins1*(, Elena A. Belousova2, Anthony I. S. Kemp1 and J. Brendan Murphy3 Two fundamentally different orogenic systems have existed on Earth throughout the Phanerozoic. Circum-Pacific accretionary orogens are the external orogenic system formed around the Pacific rim, where oceanic lithosphere semicontinuously subducts beneath continental lithosphere. In contrast, the internal orogenic system is found in Europe and Asia as the collage of collisional mountain belts, formed during the collision between continental crustal fragments. External orogenic systems form at the boundary of large underlying mantle convection cells, whereas internal orogens form within one supercell. Here we present a compilation of hafnium isotope data from zircon minerals collected from orogens worldwide. We find that the range of hafnium isotope signatures for the external orogenic system narrows and trends towards more radiogenic compositions since 550 Myr ago. By contrast, the range of signatures from the internal orogenic system broadens since 550 Myr ago. We suggest that for the external system, the lower crust and lithospheric mantle beneath the overriding continent is removed during subduction and replaced by newly formed crust, which generates the radiogenic hafnium signature when remelted. For the internal orogenic system, the lower crust and lithospheric mantle is instead eventually replaced by more continental lithosphere from a collided continental fragment. Our suggested model provides a simple basis for unravelling the global geodynamic evolution of the ancient Earth. resent-day orogens of contrasting character can be reduced to which probably began by the Early Ordovician12, and the Early two types on Earth, dominantly accretionary or dominantly Paleozoic accretionary orogens in the easternmost Altaids of Pcollisional, because only the latter are associated with Wilson Asia13. -
Initial Growth of the Northern Lhasaplano, Tibetan Plateau in the Early Late Cretaceous (Ca
hu-B35124.1 2nd pages / 1 of 14 Initial growth of the Northern Lhasaplano in the early Late Cretaceous Initial growth of the Northern Lhasaplano, Tibetan Plateau in the early Late Cretaceous (ca. 92 Ma) Wen Lai1, Xiumian Hu1,†, Eduardo Garzanti2, Gaoyuan Sun1,3, Carmala N. Garzione4, Marcelle BouDagher Fadel5, and Anlin Ma1 1State Key Laboratory of Mineral Deposits Research, School of Earth Sciences and Engineering, Nanjing University, Nanjing 210023, China 2Department of Earth and Environmental Sciences, Università di Milano-Bicocca, Milano 20126, Italy 3College of Oceanography, Hohai University, Nanjing 210098, China 4Department of Earth and Environmental Sciences, University of Rochester, Rochester, New York 14627, USA 5Department of Geological Sciences, University College London, London WC1E6BT, UK ABSTRACT INTRODUCTION Stable isotopes in lacustrine carbonates suggest that the basins surrounding the Gangdese Moun Constraining the growth of the Tibetan The Tibetan Plateau, with an average ele tains in the southern Lhasa terrane had reached Plateau in time and space is critical for test- vation of ~5000 m, is the world’s highest and an elevation >4500 m since IndiaAsia collision ing geodynamic models and climatic changes widest orogenic plateau, and exerts a major in (Ding et al., 2014). Lowtemperature thermo at the regional and global scale. The Lhasa fluence on the Asian monsoon, global climate chronology reveal that the central and northern block is a key region for unraveling the early change, and regional distribution of living spe Lhasa terranes experienced rapid to moderate history of the Tibetan Plateau. Distinct from cies (Raymo and Ruddiman, 1992; Molnar et al., cooling and exhumation between 85 and 45 Ma the underlying shallow-marine limestones, 1993; An et al., 2001; DupontNivet et al., 2007; (Hetzel et al., 2011; Rohrmann et al., 2012). -
Geologists Suggest Horseshoe Abyssal Plain May Be Start of a Subduction Zone 8 May 2019, by Bob Yirka
Geologists suggest Horseshoe Abyssal Plain may be start of a subduction zone 8 May 2019, by Bob Yirka against one another. Over by the Iberian Peninsula, the opposite appears to be happening—the African and Eurasian plates are pulling apart as the former creeps east toward the Americas. Duarte noted that back in 2012, other researchers conducting seismic wave tests found what appeared to be a dense mass of unknown material beneath the epicenter of the 1969 quake. Some in the field suggested it could be the start of a subduction zone. Then, last year, another team conducted high-resolution imaging of the area and also found evidence of the mass, confirming that it truly existed. Other research has shown that the area just above the mass experiences routine tiny earthquakes. Duarte suggests the evidence to date indicates that the bottom of the plate is peeling away. This could happen, he explained, due to serpentinization in which water percolates through plate fractures and reacts with material beneath the surface, resulting A composite image of the Western hemisphere of the in the formation of soft green minerals. The soft Earth. Credit: NASA mineral layer, he suggests, is peeling away. And if that is the case, then it is likely the area is in the process of creating a subduction zone. He reports that he and his team members built models of their A team of geologists led by João Duarte gave a ideas and that they confirmed what he suspected. presentation at this past month's European The earthquakes were the result of the process of Geosciences Union meeting that included a birthing a new subduction zone. -
Preliminary Catalog of the Sedimentary Basins of the United States
Preliminary Catalog of the Sedimentary Basins of the United States By James L. Coleman, Jr., and Steven M. Cahan Open-File Report 2012–1111 U.S. Department of the Interior U.S. Geological Survey U.S. Department of the Interior KEN SALAZAR, Secretary U.S. Geological Survey Marcia K. McNutt, Director U.S. Geological Survey, Reston, Virginia: 2012 For more information on the USGS—the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1–888–ASK–USGS. For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprod To order this and other USGS information products, visit http://store.usgs.gov Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner. Suggested citation: Coleman, J.L., Jr., and Cahan, S.M., 2012, Preliminary catalog of the sedimentary basins of the United States: U.S. Geological Survey Open-File Report 2012–1111, 27 p. (plus 4 figures and 1 table available as separate files) Available online at http://pubs.usgs.gov/of/2012/1111/. iii Contents Abstract ...........................................................................................................................................................1 -
Kinematic Reconstruction of the Caribbean Region Since the Early Jurassic
Earth-Science Reviews 138 (2014) 102–136 Contents lists available at ScienceDirect Earth-Science Reviews journal homepage: www.elsevier.com/locate/earscirev Kinematic reconstruction of the Caribbean region since the Early Jurassic Lydian M. Boschman a,⁎, Douwe J.J. van Hinsbergen a, Trond H. Torsvik b,c,d, Wim Spakman a,b, James L. Pindell e,f a Department of Earth Sciences, Utrecht University, Budapestlaan 4, 3584 CD Utrecht, The Netherlands b Center for Earth Evolution and Dynamics (CEED), University of Oslo, Sem Sælands vei 24, NO-0316 Oslo, Norway c Center for Geodynamics, Geological Survey of Norway (NGU), Leiv Eirikssons vei 39, 7491 Trondheim, Norway d School of Geosciences, University of the Witwatersrand, WITS 2050 Johannesburg, South Africa e Tectonic Analysis Ltd., Chestnut House, Duncton, West Sussex, GU28 OLH, England, UK f School of Earth and Ocean Sciences, Cardiff University, Park Place, Cardiff CF10 3YE, UK article info abstract Article history: The Caribbean oceanic crust was formed west of the North and South American continents, probably from Late Received 4 December 2013 Jurassic through Early Cretaceous time. Its subsequent evolution has resulted from a complex tectonic history Accepted 9 August 2014 governed by the interplay of the North American, South American and (Paleo-)Pacific plates. During its entire Available online 23 August 2014 tectonic evolution, the Caribbean plate was largely surrounded by subduction and transform boundaries, and the oceanic crust has been overlain by the Caribbean Large Igneous Province (CLIP) since ~90 Ma. The consequent Keywords: absence of passive margins and measurable marine magnetic anomalies hampers a quantitative integration into GPlates Apparent Polar Wander Path the global circuit of plate motions. -
Anomalous Late Jurassic Motion of the Pacific Plate With
View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Columbia University Academic Commons Earth and Planetary Science Letters 490 (2018) 20–30 Contents lists available at ScienceDirect Earth and Planetary Science Letters www.elsevier.com/locate/epsl Anomalous Late Jurassic motion of the Pacific Plate with implications for true polar wander a,b, a,c Roger R. Fu ∗, Dennis V. Kent a Lamont–Doherty Earth Observatory, Columbia University, Paleomagnetics Laboratory, 61 Route 9W, Palisades, NY 10964, USA b Department of Earth and Planetary Sciences, Harvard University, 20 Oxford St., Cambridge, MA 02138, USA c Department of Earth and Planetary Science, Rutgers University, 610 Taylor Rd, Piscataway, NY 08854, USA a r t i c l e i n f o a b s t r a c t Article history: True polar wander, or TPW, is the rotation of the entire mantle–crust system about an equatorial axis that Received 25 May 2017 results in a coherent velocity contribution for all lithospheric plates. One of the most recent candidate Received in revised form 19 February 2018 TPW events consists of a 30◦ rotation during Late Jurassic time (160–145 Ma). However, existing Accepted 25 February 2018 ∼ paleomagnetic documentation of this event derives exclusively from continents, which compose less Available online xxxx than 50% of the Earth’s surface area and may not reflect motion of the entire mantle–crust system. Editor: B. Buffett Additional paleopositional information from the Pacific Basin would significantly enhance coverage of the Keywords: Earth’s surface and allow more rigorous testing for the occurrence of TPW. -
Paleomagnetic Constraints on the Mesozoic Drift of the Lhasa Terrane (Tibet) from Gondwana to Eurasia
Paleomagnetic constraints on the Mesozoic drift of the Lhasa terrane (Tibet) from Gondwana to Eurasia Zhenyu Li1, Lin Ding1,2*, Peter C. Lippert3, Peiping Song1, Yahui Yue1, and Douwe J.J. van Hinsbergen4 1Key Laboratory of Continental Collision and Plateau Uplift (LCPU), Institute of Tibetan Plateau Research, Chinese Academy of Sciences (ITPCAS), Beijing 100101, China 2Center for Excellence in Tibetan Plateau Earth Sciences, Chinese Academy of Sciences, Beijing 100101, China 3Department of Geology and Geophysics, University of Utah, Salt Lake City, Utah 84112-9057, USA 4Department of Earth Sciences, Utrecht University, Heidelberglaan 2, 3584 CS Utrecht, Netherlands ABSTRACT Himalaya (the northernmost continental rocks The Mesozoic plate tectonic history of Gondwana-derived crustal blocks of the Tibetan derived from the Indian plate) that collided with Plateau is hotly debated, but so far, paleomagnetic constraints quantifying their paleolati- Lhasa in the Eocene along the Indus-Yarlung tude drift history remain sparse. Here, we compile existing data published mainly in Chinese suture zone (Yin and Harrison, 2000; Hu et al., literature and provide a new, high-quality, well-dated paleomagnetic pole from the ca. 180 2015; Huang et al., 2015). Ma Sangri Group volcanic rocks of the Lhasa terrane that yields a paleolatitude of 3.7°S Most authors describe an ideal Wilson-cycle ± 3.4°. This new pole confirms a trend in the data that suggests that Lhasa drifted away scenario, wherein the blocks of the Tibetan Pla- from Gondwana in Late Triassic time, instead of Permian time as widely perceived. A total teau all drifted from India in Paleozoic to Meso- northward drift of ~4500 km between ca. -
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 -
Post-Collisional Potassic Magmatism in the Eastern Lhasa Terrane, South Tibet: Products of Partial Melting of Mélanges in a Continental Subduction Channel
Gondwana Research 41 (2017) 9–28 Contents lists available at ScienceDirect Gondwana Research journal homepage: www.elsevier.com/locate/gr Post-collisional potassic magmatism in the eastern Lhasa terrane, South Tibet: Products of partial melting of mélanges in a continental subduction channel Lihong Zhang a,b, Zhengfu Guo a,⁎,MaoliangZhanga,b, Zhihui Cheng a,b, Yutao Sun a,b a Key Laboratory of Cenozoic Geology and Environment, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China b University of Chinese Academy of Sciences, Beijing 100049, China article info abstract Article history: Post-collisional, potassic magmatic rocks widely distributed in the eastern Lhasa terrane provide significant Received 29 May 2015 information for comprehensive understanding of geodynamic processes of northward subduction of the Indian Received in revised form 18 October 2015 lithosphere and uplift of the Tibetan Plateau. A combined dataset of whole-rock major and trace elements, Accepted 3 November 2015 Sr–Nd–Pb isotopes, and in situ zircon U–Pb dating and Hf–O isotopic analyses are presented for the Yangying Available online 23 December 2015 potassic volcanic rocks (YPVR) in the eastern part of the Lhasa terrane, South Tibet. These volcanic rocks consist of trachytes, which are characterized by high K O(5.46–9.30 wt.%), SiO (61.34–68.62 wt.%) and Al O (15.06– Keywords: 2 2 2 3 – – Post-collisional potassic magmatism 17.36 wt.%), and relatively low MgO (0.47 2.80 wt.%) and FeOt (1.70 4.90 wt.%). Chondrite-normalized rare Zircon U–Pb dating earth elements (REE) patterns display clearly negative Eu anomalies. -
3.16 Oceanic Plateaus A.C.Kerr Cardiffuniversity,Wales,UK
3.16 Oceanic Plateaus A.C.Kerr CardiffUniversity,Wales,UK 3.16.1 INTRODUCTION 537 3.16.2 FORMATION OF OCEANIC PLATEAUS 539 3.16.3 PRESERVATIONOFOCEANIC PLATEAUS 540 3.16.4GEOCHEMISTRY OF CRETACEOUSOCEANICPLATEAUS 540 3.16.4.1 GeneralChemicalCharacteristics 540 3.16.4.2 MantlePlumeSource Regions ofOceanic Plateaus 541 3.16.4.3 Caribbean–ColombianOceanic Plateau(, 90 Ma) 544 3.16.4.4OntongJavaPlateau(, 122 and , 90 Ma) 548 3.16.5THE INFLUENCE OF CONTINENTALCRUST ON OCEANIC PLATEAUS 549 3.16.5.1 The NorthAtlantic Igneous Province ( , 60 Ma to Present Day) 549 3.16.5.2 The KerguelenIgneous Province ( , 133 Ma to Present Day) 550 3.16.6 IDENTIFICATION OF OCEANIC PLATEAUS IN THE GEOLOGICAL RECORD 551 3.16.6.1 Diagnostic FeaturesofOceanic Plateaus 552 3.16.6.2 Mafic Triassic Accreted Terranesinthe NorthAmericanCordillera 553 3.16.6.3 Carboniferous to CretaceousAccreted Oceanic Plateaus inJapan 554 3.16.7 PRECAMBRIAN OCEANICPLATEAUS 556 3.16.8ENVIRONMENTAL IMPACT OF OCEANICPLATEAU FORMATION557 3.16.8.1 Cenomanian–TuronianBoundary (CTB)Extinction Event 558 3.16.8.2 LinksbetweenCTB Oceanic PlateauVolcanism andEnvironmentalPerturbation 558 3.16.9 CONCLUDING STATEMENTS 560 REFERENCES 561 3.16.1 INTRODUCTION knowledge ofthe oceanbasins hasimproved over the last 25years,many moreoceanic plateaus Although the existence oflarge continentalflood havebeenidentified (Figure1).Coffinand basalt provinceshasbeenknownfor some Eldholm (1992) introduced the term “large igneous considerabletime, e.g.,Holmes(1918),the provinces” (LIPs) asageneric term encompassing recognition thatsimilarfloodbasalt provinces oceanic plateaus,continentalfloodbasalt alsoexist belowthe oceans isrelatively recent. In provinces,andthoseprovinceswhich form at the early 1970s increasingamounts ofevidence the continent–oceanboundary (volcanic rifted fromseismic reflection andrefraction studies margins).