saved book title Earth subtitle cover image The Earth seen from Apollo 17.jpg cover color Black Earth Overview Earth Characteristics Earth physical characteristics tables Earth s orbit Earth s rotation Axial tilt Figure of the Earth Landform List of landforms Extreme points of Earth Hydrosphere Biosphere Abundance of the chemical elements Human geography Structure Structure of the Earth Crust geology Crust Mohorovi i discontinuity Mantle geology Mantle Mesosphere mantle Mesosphere Mantle convection Asthenosphere Core mantle boundary Outer core Inner core Plate tectonics Plate reconstruction Plate tectonics Supercontinent Superocean List of supercontinents Supercontinent cycle List of tectonic plates List of tectonic plate interactions Atmosphere Atmosphere of Earth Weather Climate Exosphere Thermosphere Mesosphere Stratosphere Troposphere Ionosphere Magnetic field Earth s magnetic field Geomagnetic pole North Magnetic Pole South Magnetic Pole Geomagnetic reversal History History of the Earth Geological history of Earth Timeline of natural history Future of the Earth Category Wikipedia books on astronomy Earth Category Wikipedia books on Earth sciences Earth ... more details
Rodina Bulgarian language Bulgarian , lang ru , Motherland may refer to one of the following Rodina , a political party of Russia Mother Motherland monuments in a number of cities of former Soviet Union Rodina magazine Rodina magazine , a Russian historical illustrated magazine Rodina class motorship , a Russian river passenger ship Rodina, a village in Arini Commune, Maramure County, Romania See also Rodinia , ancient supercontinent derived from Rodina disambig de Rodina Begriffskl rung fr Rodina homonymie ru tg ... more details
Taxobox name Batrachosuchus fossil range Late Triassic image Batrachosuchus1DB.jpg image width 250px regnum Animal ia phylum Chordate Chordata classis Amphibia ordo Temnospondyli familia Brachyopidae genus Batrachosuchus Batrachosuchus is an extinct genus of temnospondyli temnospondyl amphibian from the Triassic of South Africa . is this supposed to be Batrachosuchus or Batrachosaurus? Sources Wildlife of Gondwana Dinosaurs and Other Vertebrates from the Ancient Supercontinent Life of the Past by Pat Vickers Rich, Thomas Hewitt Rich, Francesco Coffa, and Steven Morton Trematosauria Category Temnospondyls Category Triassic amphibians Category Prehistoric amphibians of Africa paleo amphibian stub Triassic stub portal Paleontology fr Batrachosuchus ... more details
italictitle Taxobox name Bematherium regnum Animal ia phylum Chordate Chordata classis Mammal ia infraclassis Marsupialia ordo Diprotodontia subordo Vombatiformes familia Diprotodontidae genus Bematherium Bematherium is an extinct genus of marsupial . Sources Wildlife of Gondwana Dinosaurs and Other Vertebrates from the Ancient Supercontinent Life of the Past by Pat Vickers Rich, Thomas Hewitt Rich, Francesco Coffa, and Steven Morton Prehistoric Mammals of Australia and New Guinea One Hundred Million Years of Evolution by John A. Long, Michael Archer, Timothy Flannery, and Suzanne Hand portal Paleontology Category Prehistoric vombatiforms paleo marsupial stub nl Bematherium ... more details
Orphan date February 2009 The Sprite Possum Ektopodontid is an extinct genus of marsupial from the early Miocene . Sources Prehistoric Mammals of Australia and New Guinea One Hundred Million Years of Evolution by John A. Long, Michael Archer, Timothy Flannery, and Suzanne Hand The Origin and Evolution of Mammals Oxford Biology by T. S. Kemp Wildlife of Gondwana Dinosaurs and Other Vertebrates from the Ancient Supercontinent Life of the Past by Pat Vickers Rich, Thomas Hewitt Rich, Francesco Coffa, and Steven Morton Category Prehistoric mammals of Australia Category Prehistoric diprotodonts Category Miocene extinctions Category Miocene mammals paleo marsupial stub ... more details
Italic title Taxobox name Thoracopterus image Thoracopterus magnificus.JPG image caption Thoracopterus magnificus regnum Animal ia phylum Chordate Chordata subphylum Vertebrate Vertebrata classis Actinopterygii ordo Perleidiformes familia Thoracopteridae genus Thoracopterus genus authority Heinrich Georg Bronn Bronn , 1858 Thoracopterus is an extinct genus of bony fish . References Fishes of the World by Joseph S. Nelson page 95 Wildlife of Gondwana Dinosaurs and Other Vertebrates from the Ancient Supercontinent Life of the Past by Pat Vickers Rich, Thomas Hewitt Rich, Francesco Coffa, and Steven Morton The Rise of Fishes 500 Million Years of Evolution by John A. Long portal Paleontology Category Ray finned fish Category Triassic fish paleo rayfinned fish stub triassic stub ... more details
to split Pangaea in two, and the growing Atlantic Ocean separated the northern supercontinent of Laurasia from the southern supercontinent Gondwana. Around 150 Ma Gondwana also began to rift apart ... Geology of the Himalaya Tethys Ocean Paleo Tethys Ocean Pangaea Pangaea Ultima Supercontinent ... more details
Voo, Conall Mac Niocaill, Joseph G. Meert year 1998 month January title The Proterozoic supercontinent .... Around 2.45 Ga, Arctica was part of the major supercontinent Kenorland . Around 2.1 Ga, when Kenorland shattered, the Arctican craton was part of the minor supercontinent Nena supercontinent ... was part of the major supercontinent columbia supercontinent Columbia . Around 1.5 Ga, Laurentia was an independent continent. Around 1.1 Ga, Laurentia was part of the major supercontinent Rodinia . Around 750 Ma, Laurentia was part of the minor supercontinent Protolaurasia . Laurentia nearly rifted apart. Around 600 Ma, Laurentia was part of the major supercontinent Pannotia . Around ... 416 2.8 to 359.2 2.5 Ma , Laurentia collided against Baltica, forming the minor supercontinent ... other for forming the major supercontinent Pangaea . Around Jurassic 199.6 0.6 to 145.5 4 Ma ... supercontinent Laurasia. Around Cretaceous 145.5 4 to 65.5 0.3 Ma , Laurentia was an independent ... supercontinent America. Around 250 Ma from now, all continents may crash together, forming the major supercontinent Pangaea Ultima . Laurentia would be part of Pangaea Ultima. Around 450 600 Ma from ... more details
A. V. title The supercontinent medley Recent views journal Current Science year 2003 volume 85 issue ... East Gondwana supercontinent assembly and breakup publisher Geological Society of London volume ... more details
italictitle Taxobox name Secernosaurus fossil range Late Cretaceous regnum Animal ia phylum Chordate Chordata classis Reptile Sauropsida superordo Dinosaur ia ordo Ornithischia subordo Ornithopoda infraordo Iguanodont ia superfamilia Hadrosauroidea familia Hadrosauridae genus Secernosaurus genus authority Brett Surman, 1979 subdivision ranks Species subdivision S. koerneri small Brett Surman, 1979 type species type small Secernosaurus meaning severed lizard is a genus of herbivore herbivorous dinosaur . Secernosaurus was a hadrosaur , a duck billed dinosaur which lived during the Late Cretaceous . Its fossils have been found in Argentina . Its name comes from the fact that it lived in South America , which during the Mesozoic Era was part of the southern supercontinent of Gondwana . Most other hadrosaurs lived in the northern supercontinent of Laurasia , so it was separated from its relatives. The type species is Secernosaurus koerneri , described in 1979. A species named in 1984, Kritosaurus australis , is thought to be synonymous. ref name AMGS10 cite journal last Prieto Marquez first Alberto coauthors and Salinas, Guillermo C. year 2010 title A re evaluation of Secernosaurus koerneri and Kritosaurus australis Dinosauria, Hadrosauridae from the Late Cretaceous of Argentina journal Journal of Vertebrate Paleontology volume 30 issue 3 pages 813 837 doi 10.1080 02724631003763508 ref References Reflist http www.thescelosaurus.com hadrosauridae.htm Hadrosauridae at Thescelosaurus Portal Dinosaurs Category Cretaceous dinosaurs Category Hadrosaurs Category Dinosaurs of South America ornithopod stub ca Secernosaure de Secernosaurus es Secernosaurus it Secernosaurus koerneri pl Secernozaur pt Secernossauro zh ... more details
The Pan African orogeny was a series of major Neoproterozoic orogeny orogenic events mountain building which related to the formation of the supercontinent s Gondwana and Pannotia about 600 million years ago. sfn Glossary The Mozambique Belt , extending from east Antarctica through East Africa up to the Arabian Nubian Shield , formed as a suture between plates during the Pan African orogeny. sfn Cutten 2002 The Mozambique ocean began closing between Madagascar India and the Congo craton Congo Tanzania craton Tanzania craton between 700 and 580 million years ago, with closure between 600 and 500 million years ago. sfn Grantham Maboko Eglington 2003 p 417 418 References reflist colwidth 30em Sources refbegin cite web ref harv url http gsa.confex.com gsa 2002AM finalprogram abstract 43792.htm title THE MOZAMBIQUE BELT, EASTERN AFRICA TECTONIC EVOLUTION OF THE MOZAMBIQUE OCEAN AND GONDWANA AMALGAMATION last Cutten first Huntly N.C. date October 29, 2002 publisher The Geological Society of America accessdate 2011 12 28 cite web ref harvid Glossary url http www.dinodata.net Golonka GLOSSARY.pdf title Glossary of Plate Tectonic and Paleogeographic Terms format PDF accessdate 2006 04 09 not available without registration free cite book ref harv url http books.google.ca books?id 4B8nrDVjaCgC&pg PA417 chapter A review of the evolution of the Mozambique Belt and implications for the amalgamation and dispersal of Rodinia and Gondwana first1 G.H. last1 Grantham first2 M. last2 Maboko first3 B.M. last3 Eglington title Proterozoic East Gondwana supercontinent assembly and breakup publisher Geological Society year 2003 ISBN 1862391254 refend Category Orogeny Category Geology of Africa Category Proterozoic tectonics stub he ... more details
Unreferenced stub auto yes date December 2009 about the total area of a geographical area land mass the ambient album by Steve Roach Landmass album A landmass is a contiguous area of land surrounded by ocean . Although it may be most often written as one word to distinguish it from the usage land mass the measure of land area it is also used as two words. Landmasses include supercontinent s continent s island s Category Landforms Geo term stub be be x old bg bs Kopno cy Ehangdir da Landjord de Landfl che et Maismaa eo eflando is Meginland ka lv Sauszeme lt Sausuma xmf nds nl Vaastelaand ja no Fastland nds Landmasse pl L d ru sk Kontinent sl Kopno sr fi Manner sv Fastland uk vi L c a fiu vro Mais maa zh yue zh ... more details
italic title Taxobox name Niolamia fossil range ? Cretaceous or Eocene image Niolamia.jpg image width 250px image caption Skull regnum Animal ia phylum Chordata classis Sauropsida ordo Testudines subordo Cryptodira familia Meiolaniidae genus Niolamia genus authority Florentino Ameghino Ameghino , 1899 subdivision ranks species subdivision N. argentina Niolamia is an extinct genus of South America n Meiolaniidae meiolaniid turtle. ref http www.bioone.org doi abs 10.1080 039.031.0618 ref Woodward sunk it into Meiolania , but this was not accepted by later authors. ref Cite doi 10.3853 j.0067 1975.14.1925.844 ref Image Meiolania5.jpg thumb left Restoration by Heinrich Harder References references Turtles, Tortoises and Terrapins Survivors in Armor by Ronald Orenstein Pg. 43 Wildlife of Gondwana Dinosaurs and Other Vertebrates from the Ancient Supercontinent Life of the Past by Pat Vickers Rich, Thomas Hewitt Rich, Francesco Coffa, and Steven Morton Portal box Paleontology Turtles Extinct turtles Category Eocene reptiles Category Meiolaniidae paleo turtle stub ... more details
Gabriele Susanne Kerner born 1960 is a German singer better known as Nena . Nena may also refer to Nena band , the band organized by the singer, active from 1982 until 1987 Nena album Nena album , the debut album of the band. Songs Nena song Nena song , by Miguel Bos Searching for Nena , a song by Nick Warren Other Nena people , an ethnic group in Tanzania Nena of Nata and Nena , Aztec mythical figure a.k.a. Citlalicue Acronym NENA as an acronym may refer to Nena supercontinent , derived from Northern Europe and North America National Emergency Number Association , USA Nokomis East Neighborhood Association , in Minneapolis Northeastern Neo Aramaic language group People People bearing the given name or surname Nena are listed at Nena given name Nena surname See also Nina disambiguation Isla Nena Air , an airline in Puerto Rico disambig ca Nena desambiguaci de Nena Begriffskl rung es Nena desambiguaci n fa it Nena disambigua nl Nena ... more details
File Pangaea 230 million years ago .png thumb right 350px Map of Pangaea, including the Central Pangean Mountains. The Central Pangean Mountains were an extensive northeast southwest trending mountain range in the central portion of the supercontinent Pangaea during the Triassic period. They were formed as a result of collision between the minor supercontinents Laurussia and Gondwana during the formation of Pangaea. ref http science.jrank.org pages 2595 Europe.html Europe Forces That Made Europe, The Mediterranean Desert Miscellaneous regions and events ref Remnants of this massive mountain range include the Appalachian Mountains of North America and the Little Atlas of Morocco , Africa . A number of mountain building periods were involved in the formation of the Central Pangean Mountains, including the Acadian orogeny Acadian , Caledonian orogeny Caledonian and Alleghenian orogeny Alleghenian orogeny orogenies . References reflist Major African geological formations Category Mountain ranges of North America Category Mountain ranges of Africa Category Mountain ranges of Europe Category Triassic Palaeo geo stub Triassic stub ... more details
Image Florida Platform.jpg thumb right The structure of the Florida platform, the foundation of which came from the African plate over 200 million years ago During the early Mesozoic Era 251 65.5 mya unit mya the supercontinent of Pangea began to rift and break apart. As North America separated from Africa a small portion of the African plate detached and was carried away with the North American plate . This provided some of the foundation upon which Florida now rests. ref cite web url http www.dep.state.fl.us geology geologictopics geohist 2.htm title Florida s Geologic History author Means,Guy H. publisher Florida Dept. of Environmental Protection date August 30, 2010 accessdate August 12, 2011 ref References reflist United States topic title Geology of the United States by political division prefix Geology of Category History of Florida Category Geology of Florida Florida stub geology stub ... more details
Euramerica also known as Laurussia not to be mistaken as Laurasia , the Old Red Continent or the Old Red Sandstone Continent was a minor supercontinent created in the Devonian as the result of a collision between the Laurentia n, Baltica , and Avalonia craton s Caledonian orogeny . 300 million years ago in the Late Carboniferous tropical rainforest s lay over the equator of Euramerica. A major, abrupt change in vegetation occurred when the climate aridified. The forest fragmented and the Lycopodiophyta lycopsids which dominated these wetlands thinned out, being replaced by opportunistic ferns. There was also a great loss of amphibian diversity and simultaneously the drier climate spurred the diversification of reptiles. ref name SahneyBentonFerry2010LinksDiversityVertebrates cite journal url http geology.geoscienceworld.org cgi content abstract 38 12 1079 author Sahney, S., Benton, M.J. & Falcon Lang, H.J. year 2010 title Rainforest collapse triggered Pennsylvanian tetrapod diversification in Euramerica journal Geology volume 38 pages 1079 1082 format PDF doi 10.1130 G31182.1 issue 12 ref Extent Image Euramerica en.svg thumb 300px Euramerica in the Devonian Euramerica became a part of the major supercontinent Pangaea in the Permian . In the Jurassic , when Pangaea rifted into two continents , Gondwana and Laurasia , Euramerica was a part of Laurasia. In the Cretaceous , Laurasia split into the continents of North America and Eurasia . The Laurentian craton became a part of North America while Baltica became a part of Eurasia, and Avalonia was split between the two. Events Carboniferous Climate change devastated tropical rainforests, fragmenting the forests into isolated islands and causing the extinction of many plant and animal species during the Carboniferous Rainforest Collapse CRC . Permian Euramerica became a part of the major supercontinent Pangaea Jurassic Pangaea rifted into Gondwana and Laurasia Cretaceous Laurasia split into the continents of North America ... more details
Vaalbara is theorized to be Earth s first supercontinent , beginning its formation about mya 3600 million years ago , completing its formation by about mya 3100 million years ago and breaking up by mya 2500 million years ago . The name Vaalbara is derived from the South African Kaapvaal craton and the West Australian Pilbara craton . These craton s were combined during the time of the Vaalbara supercontinent. Identical radioactive dating radiometric ages of mya 3470 error 2 million years ago have been obtained for the ejecta from the oldest impact event s in each craton. Remarkably similar structural sequences between these two cratons have been noted for the period between 3,500 to 2,700 million years ago. Paleomagnetism Paleomagnetic data from two ultramafic rock ultramafic complexes in the cratons showed that at mya 3870 million years the two cratons could have been part of the same supercontinent. The reconstructed apparent polar wander path for the two cratons shows marked similarities. Both the Pilbara and Kaapvaal cratons show extensional fault s which were active about during ... in geologic periods of orogenesis mountain building to form supercontinents. The cycle of supercontinent ... the Pilbara region is coloured in red. gallery Vaalbara is the Earth s theorized first supercontinent . ref name enotes It was a complete supercontinent by mya 3100 million years ago . Vaalbara formed ... years the two cratons could have been part of the same supercontinent. ref name mega cite journal title ... felsic volcanism and coeval with the impact layers. ref name mega Supercontinent formation Cratons ... enotes.com Science pages 1 2 accessdate February 28, 2010 ref A supercontinent is a landmass composed ... Eventually the lithosphere begins to dome upward, it cracks, magma wells upward and fragments of the supercontinent ... March 7, 2010 ref This cycle &ndash the Wilson Cycle &ndash of supercontinent formation, breakup ... Columbia supercontinent References references Bailey, R.C., Cruden, A.R., and B. Nitescu. 2006 Crustal ... more details
Unreferenced date August 2008 South China continent , also known as South China craton , South Chinese craton , or Yangtze craton , was an ancient continent craton that contained today s Northern and southern China South and Southeast China named after , Indochina , and parts of Southeast Asia i.e. Borneo and adjacent islands . South China had been part of many past supercontinents, including Rodinia , Pannotia , Gondwana , Pangaea , Laurasia , and Eurasia . File .png thumb 250px South China craton in Russian File Yangtse craton location.jpg thumb 250px About a billion years ago Late Proterozoic , the supercontinent, Rodinia formed. South China was part of the supercontinent. South China was bordered by Mirovia Ocean to the north, Siberia continent Siberia to the east, Australia to the west, and Laurentia to the south as shown here in the Rodinia paleogeography. 750 million years ago, Rodinia rifted and South China became an isolated continent. A hundred million years later, these fragmented pieces of continent assembled back together to create the supercontinent of Pannotia . South China collided North China and Eastern Gondwana mainly Australia . When Pannotia disintegrated 550 million years ago, South China and North China continent North China became part of and remained with Eastern Gondwana for millions of years. Late in the Silurian 175 million years later after Pannotia s disintegration , South China and North China , rifted away from Gondwana and moved across the ancient, shrinking Proto Tethys Ocean . A new ocean was forming in its southern end, Paleo Tethys Ocean . By the Late Carboniferous 300 million years ago , while North China collided with Siberia and Kazakhstania , completely closing the Proto Tethys, South China became an independent continent. For much of the Permian Period, South China remained in the tropical latitudes. And also, while most of the giant lycopods of the Carboniferous disappeared, giant lycopods rema ... more details
Infobox historical continent name Laurasia image Image Laurasia Gondwana.svg 250px caption Map of Pangaea with Laurasia and Gondwana. formation year 500 Mya type Geology Geologica l supercontinent today Europe without Balkan Peninsula Balkans br Asia br North America smaller continents Laurentia br Baltica br Kazakhstania br Siberia continent Siberia br North China craton North China br South China continent South China br East China craton East China plate Eurasian Plate br North American Plate In paleogeography , Laurasia IPAc en icon l r e or IPAc en l r e i ref OED ref was the northernmost of two supercontinent s the other being Gondwana that formed part of the Pangaea supercontinent from approximately Ma 510 200 Mya . It separated from Gondwana Ma 200 180 Mya the late Triassic era geology era during the breakup of Pangaea, drifting further north after the split. ref cite web last Houseman first Greg url http homepages.see.leeds.ac.uk eargah Gond.html title Dispersal of Gondwanaland publisher University of Leeds accessdate 21 Oct 2008 ref The name combines the names of Laurentia , the name given to the North American craton , and Eurasia . As suggested by the geologic naming, Laurasia included most of the landmasses which make up today s continents of the Northern Hemisphere , chiefly Laurentia i.e. the core North American continent , Baltica , Siberia continent Siberia , Kazakhstania , and the North China craton North China and East China craton East China cratons. Origin Although Laurasia is known as a Mesozoic phenomenon, today it is believed that the same continents that formed the later Laurasia also existed as a coherent supercontinent after the breakup of Rodinia around 1 billion years ago. To avoid confusion with the Mesozoic continent, this is referred to as Proto Laurasia . It is believed that Laurasia did not break up again before it recombined with the southern continents to form the late Precambrian supercontinent of Pannotia , w ... more details
formed a single supercontinent which he called the Urkontinent , before later breaking up and drifting ... and their breaking up appears to be supercontinent cycle cyclical through Earth s 4.6 billion ... last supercontinent, called Columbia supercontinent Columbia or Nuna, appears to have assembled in the period ... Rodinia supercontinent. Earth Science Reviews , v. 59, p. 125 162 accessdate 2007 01 07 ref ref ... title A Paleo Mesoproterozoic supercontinent assembly, growth and breakup. Earth Science Reviews , v. 67, p. 91 123 accessdate 2007 01 08 ref Columbia Nuna broke up and the next supercontinent, Rodinia ... up, it split into three pieces the supercontinent of Proto Laurasia , the supercontinent of Proto ... Ocean . Most of the above masses coalesced again to form the relatively short lived supercontinent of Pannotia . This supercontinent included large amounts of land near the poles and only a relatively ... , Baltica , and the southern supercontinent of Gondwana . In the Cambrian period, the continent ... by the end of the Ordovician to form a minor supercontinent called Euramerica or Laurussia, closing ... had been a separate continent for millions of years since the deformation of the supercontinent Pannotia ... the formation of the Ural Mountains , and the formation of the supercontinent of Laurasia. This was the last ... supercontinent of Gondwana separated into multiple continents Africa, South America, India, Antarctica ... History of Earth Supercontinent cycle PANGAEA data library PANGAEA , a data library for earth ... more details
Ma, and that most of the Earth s landmasses collected into a single supercontinent around 1000 Ma. The supercontinent, known as Rodinia , broke up around 600 Ma. A number of glaciation glacial periods ... has caused the formation and break up of continents over time, including occasional formation of a supercontinent that contains most or all of the continents. The earliest known supercontinent was Vaalbara . It formed from proto continents and was a supercontinent by 3.1 billion years ago 3.1 Giga annum Ga . Vaalbara broke up 2.8 Giga annum Ga ago. The supercontinent Kenorland was formed 2.7 Giga ... Laurentia , Baltica , Yilgarn craton Australia , and Kalahari craton Kalahari . The supercontinent Columbia supercontinent Columbia or Nuna formed during a period of 2.0&ndash 1.8 billion years and broke ... implications for a pre Rodinia supercontinent journal Earth Science Reviews volume 59 pages 125 ... supercontinent assembly, growth and breakup journal Earth Science Reviews volume 67 pages 91 123 doi 10.1016 j.earscirev.2004.02.003 bibcode 2004ESRv...67...91Z ref The supercontinent Rodinia is thought ... Commons category Precambrian External links http www.scotese.com precambr.htm Late Precambrian Supercontinent ... more details
Geological era The Mesoproterozoic Era is a geology geologic era geology era that occurred between 1600 Ma and 1000 annum Ma million years ago . The Mesoproterozoic was the first period of Earth s history with a respectable geological record. Continents existed in the Paleoproterozoic , but we know little about them. The continental masses of the Mesoproterozoic are more or less the same ones that are with us today. The major events of this era are the formation of the Rodinia supercontinent , the breakup of the Columbia supercontinent Columbia supercontinent , and the evolution of sexual reproduction . This era is marked by the further development of continental plates and plate tectonics. At the end of this era, the continental plates that had developed were more or less the same we have today. This is the first era of which a good geological record still exists today. The first large scale mountain building episode, the Grenville Orogeny , for which extensive evidence still survives happened in this period. This era was the high point of the Stromatolites before they declined in the Neoproterozoic . The era saw the development of sexual reproduction, which greatly increased the complexity of life to come. It was the start of development of communal living among organisms, the multicellular organisms . It was an Era of apparently critical, but still poorly understood, changes in the chemistry of the sea, the sediments of the earth, and the composition of the air. Oxygen levels had risen to perhaps 1 of today s levels at the beginning of the era and continued rising throughout the Era. Subdivisions The subdivisions of the Mesoproterozoic are, obviously, arbitrary divisions based on time. They are not geo or biostratigraphic units. The base of the Mesoproterozoic is defined chronometrically, in terms of years, rather than by the appearance or disappearance of some organism. This gives an illusory sense of certainty. Radiometric dating is a good tool, and gets better ... more details
, to become a part of the supercontinent Columbia supercontinent Columbia , 1500 Ma Baltica The Nena supercontinent Nena Continent composed of Arctica , East Antarctica and Baltica, was splitoff from ... more details
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