====== BCE Events (Millions of Years) ====== Before Common Era (BCE) events more than a million years ago. ==== Ancestral Bottleneck, 1.2M BCE ==== Genome research with the Alu gene indicates human ancestors were an endangered species roughly 1.2 million years ago, with a breeding pool of as little as 18,500 individuals. Worse, the condition might have persisted for nearly a million years, indicating how fragile our early development as a species may have been. [[http://www.physorg.com/news183278038.html]] ==== Pingualuit Crater, 1.4M BCE ==== Canadian impact crater in Quebec with a Secchi depth visibility >115ft, recharged solely by snowfall and rainfall. It's noted for its nearly perfect circular dimensions with a depth of 1300ft and a diameter of just over 2mi, and was known to the Inuit as the 'pimple' and the Crystal Eye of Nunavik. ]]https://en.wikipedia.org/wiki/Pingualuit_crater]] ==== Homo erectus Diverges, 1.8M BCE ==== Earliest //Homo erectus// skeletons found, although many put the divergence at anywhere from 2.1M to 2.8M BCE. [[https://en.wikipedia.org/wiki/Homo_erectus]]\\ [[https://en.wikipedia.org/wiki/Homo_habilis]] ==== Galan Eruption, 2.2M BCE ==== Located in the Argentinian Andes, Cerro Galan is a VEI 8 that has gone from large lake to salty lagoon due to a resurgence of the eastern caldera floor. [[http://en.wikipedia.org/wiki/Gal%C3%A1n]] ==== Supernova FeMn, 2.6M BCE ==== A nearby supernova (or two) left deposits of radioactive iron-60 across the globe. The radiation itself would likely have been minimal, but a superluminal object in the heavens for up to a year (as much light as the full moon, continuously) could have had significant endocrine effects on many species. There also appears to be an associated global cooling at this time. Roughly one third of all large marine species went extinct. This marks the end of the Pliocene and the beginning of the Pleistocene. [[https://arxiv.org/ftp/arxiv/papers/0709/0709.4197.pdf]]\\ [[https://www.newscientist.com/article/2093270-supernovae-2-million-years-ago-may-have-changed-human-behaviour/?utm_source=NSNS&utm_medium=SOC&utm_campaign=hoot&cmpid=SOC%7CNSNS%7C2016-GLOBAL-hoot]]\\ [[http://www.popsci.com/supernova-might-have-abetted-mass-extinction?dom=prime&src=syn]]\\ [[https://phys.org/news/2017-06-previously-unknown-extinction-marine-megafauna.html]]\\ [[https://en.wikipedia.org/wiki/Pleistocene]]\\ [[https://phys.org/news/2018-05-supernovae-responsible-mass-extinctions.html]]\\ ==== LD 350-1, 2.8M BCE ==== Whether an ancestor or a cousin of humanity, the LD 350-1 jawbone pushes the potential for a split in human evolution to around this timeframe, perhaps as an intermediary between austrolopithicines and homo. [[https://en.wikipedia.org/wiki/Homo_habilis]]\\ [[https://en.wikipedia.org/wiki/Ledi-Geraru#LD_350-1]]\\ ==== Quarternary Glaciation, 3M BCE ==== Ice sheets develop on Greenland, supposedly due to dropping levels of CO2. The Ice Ages in general are believed to have begun around this time. Isthmus of Panama formed, perhaps creating the thermohaline current of the Atlantic as we know it. [[http://en.wikipedia.org/wiki/Quaternary_glaciation]]\\ [[http://en.wikipedia.org/wiki/Isthmus_of_Panama]]\\ ==== Lake El'gygytgyn Forms, 3.6M BCE ==== A meteor strike forms a 12km wide crater and lake, 100km north of the Arctic Circle and 360km from Pevek, Russia. The Siberian crater was drilled for sediment core analysis and climate information by Julie Brigham-Grette and her team form the University of Massachusetts Amherst. The megaladon sharks go extinct during this time. Alexandra Witze. 2010. "Siberian lake yields climate record: winter drilling project also penetrates ancient impact crater." //Science News//. 178(11):p13.\\ [[https://www.popsci.com/story/science/megalodon-alive-myth/?utm_source=digg]]\\ ==== Australpithecines Diverge, 4M BCE ==== The Australopithecines and Hominina split -- and both are considered 'Human'. [[https://en.wikipedia.org/wiki/Hominini]]\\ [[https://en.wikipedia.org/wiki/Human_evolution]]\\ [[http://en.wikipedia.org/wiki/Lake_El'gygytgyn]] ==== Heise Supervolcano Erupts, 4.5M BCE ==== The Yellowstone hot spot was in southeastern Idaho when several smaller magma pools merged and then erupted within the span of some tens of thousands -- if not thousands -- of years. Thomas Sumner. 2014. "Massive eruptions can arise suddenly: Magma merger ledt Idaho supervolcano blow, study finds." //Science News//. 186(4):p14. [[http://en.wikipedia.org/wiki/Heise_volcanic_field]] ==== Karakul / Qaraqul Impact, 5M BCE ==== The Karakul (or Quaraqul) crater in Tajikistan is a lake with a rim about 52km wide. The lake was known to the west as the Lake Victoria of the Pamirs, and factors heavily into strategic control of the region due to its large supply of freshwater. [[http://en.wikipedia.org/wiki/Karakul_(Tajikistan)]] ==== Miocene Ends / Pliocene Begins, 5.333M BCE ==== A global warm period ends, and glaciations begin. [[https://en.wikipedia.org/wiki/Miocene]]\\ ==== Chimpanzee Diversion, 6.3M BCE ==== Chimpanzees and the hominina lineage diverge. [[https://en.wikipedia.org/wiki/Hominini]] ==== Supernova Event, 8M BCE ==== A rain of iron-60 from a 'nearby' supernova may have depleted the ozone significantly, contributing higher ionizing solar radiation at higher latitudes. [[https://phys.org/news/2018-05-supernovae-responsible-mass-extinctions.html]] ==== McCullen Creek & Grey's Landing Supereruptions, 8.7-9M BCE ==== The hot spot over Yellowstone erupted twice within a 300,000y period -- the second one being among the 'top five eruptions of all time' according to Thomas Knott. The McCullen Creek eruption at 8.99Ma was a VEI 8.6, and the Grey's Landing eruption at 8.72Ma was a VEI of 8.8. Knott, Branney, et al, Geology, JUN2020. "Discovery of two new super-eruptions from Yellowstone hotspot track (USA): Is the Yellowstone hotspot waning?" [[https://doi.org/10.1130/G47384.1]]\\ ==== Homininae End, 8 to 10M BCE ==== Gorilla and human ancestors diverge. [[https://en.wikipedia.org/wiki/Homininae]] ==== Nordlinger Ries Impact Event, 14.4M BCE ==== Found in western Germany, this crater was estimated to be 24km across when it formed. Just 42km west-southwest of Nordlinger Ries lies the Steinheim crater, dated to the same time. The Nordlinger Ries impactor likely had a diameter of 1.5km, hitting at 20km/s. Of note: a local graphite deposit was struck by the impactor, creating some 72k tonnes of tiny diamonds, all less than 0.2mm wide; stone buildings in the area are full of such diamonds. [[http://en.wikipedia.org/wiki/N%C3%B6rdlinger_Ries]]\\ [[http://en.wikipedia.org/wiki/Steinheim_crater]]\\ ==== Miocene Period Begins, 23M BCE ==== The Antarctic thaws and the world warms quite a bit. [[http://en.wikipedia.org/wiki/File:All_palaeotemps.png]]\\ [[http://en.wikipedia.org/wiki/File:All_palaeotemps.png]]\\ ==== Monkey Diversion, 25M BCE ==== Old World Monkeys diverse from the ancestral hominid lineage. [[https://en.wikipedia.org/wiki/Hominini]] ==== La Garita Caldera, 27M BCE ==== Geologists argue over whether La Garita Caldera or the Siberian Traps were the largest explosive eruption in all of history. Located in US Rockies, the VEI 8 caldera is situated near La Garita, Colorado. The output of 5,000 cubic kilometers was an estimated equivalent yield of 5,000,000 megatons of TNT. ==== Hypatia Impact, 28M BCE ==== The first conclusive evidence of a comet strike on earth was published in 2013. The comet struck over Egypt, and diamonds and fused glass from its impact later adorned great pharoahs. [[http://www.foxnews.com/science/2013/10/10/first-evidence-comet-striking-earth-found-in-egypt/?intcmp=features]] [[http://en.wikipedia.org/wiki/La_Garita_Caldera]] ==== Wah Wah Springs, 30M BCE ==== A field of super volcanoes went off in what is now near Wah Wah Springs, Utah. The area forms the Indian Peak-Caliente caldera complex, with a score of calderas and evidence for more than a dozen super volcanoes. The eruption is classified as a VEI 8 at the 30M year mark, but eruptions took place from 36-18M years ago. The area is also part of the Marysvale volcanic field. [[http://geosphere.gsapubs.org/content/9/4/864.abstract]]\\ [[http://en.wikipedia.org/wiki/Marysvale_volcanic_field]] ==== ERV-FC Virus, 33M BCE ==== A retrovirus began to infect mammals, and it did so for about 15M years. [[https://en.wikipedia.org/wiki/ERV-Fc]] ==== Beginning of the Oligocene Epoch, 34M BCE ==== South American and Australia break away from Antarctica, allowing the creation of the Antarctic Circumpolar Current. This dramatically lowers the temperature of Antarctica, allowing the creation of the permanent ice sheets oer the Gamburtsev Mountains. This time frame also corresponds to a massive drop in atmospheric CO2 levels. There are indications of an impact cluster around this time, as well. Morton, Mary Caperton. September 2009. "How Antarctica Got Its Ice". //Earth//. p9\\ [[http://phys.org/news/2013-03-link-co2-mass-extinctions-species.html]] ==== Grande Coupure, 35M BCE ==== A series of collisions with large meteors creates craters in Chesapeake Bay, Siberia's Popigai Crater, and the Timor Sea, as well as a sheet of molten rock falling across much of eastern North America (such as Tom's Canyon impact crater). This, rather than the opening of the Drake Passage, may have started the real changes leading to the end of the Eocene and the beginning of the Oligocene. The Popigai impact created a massive diamond deposit. The collisions have been linked to a repeating oscillation of impacts roughly every 32 million years. [[http://en.wikipedia.org/wiki/Chesapeake_Bay_impact_crater]]\\ [[http://en.wikipedia.org/wiki/Popigai_crater]]\\ [[http://en.wikipedia.org/wiki/Toms_Canyon_impact_crater]]\\ [[http://www.physorg.com/news193556580.html]]\\ [[http://geology.com/articles/popigai-crater-diamonds/]]\\ [[http://phys.org/news/2014-05-dark-disk-milky-plane-rash.html]]\\ ==== Mistastin Crater Impact, 36M BCE ==== Labrador, Canada took a hit on a batholith, leaving behind a crater that once was an estimated 28km wide. Currently, Mistastin Lake (16km in diameter) resides at that location. [[http://en.wikipedia.org/wiki/Mistastin_crater]] ==== ACC Begins, 38M BCE ==== The Antarctic Circumpolar Current (ACC) formed when Antarctica as a landmass became isolated enough to have a circumpolar current. This current allowed the landmass to become further isolated form the warmer waters of the world, and it is this differential from the pole to the equator that cools our Ice Age world. This may be the real starter of the Oligocene 4M years later. [[http://www.physorg.com/news/2011-06-ancient-global-cooling-published-science.html]] ==== Haughton Impact, 39M BCE ==== Far northern Canada's Devon Island took a hit from a bolide estimated at 2km in diameter. The Mars Institute and SETI operate a project at this 75N latitude site because of its intense cold and lack of vegetation. [[http://en.wikipedia.org/wiki/Haughton_impact_crater]] ==== Azolla Event, 50M BCE ==== Azolla event, in which an isolated arctic sea formed a fresh-water top-layer that supported an Azolla sp of fern that sequestered as much as 80% of the world's CO2 in the anoxic bottom layer. An alternative explanation to the CO2 levels dropping is the reaction of CO2 with the earth itself, especially with newly formed volcanic rock, such as would have formed during the Deccan Flats outbreak in Indian. [[http://en.wikipedia.org/wiki/Azolla_event]]\\ Sid Perkins, 11OCT2008, "Continental clash cooled climate; When India and Asia collide, sources of CO2 disappeared", //Science News// VOL 174 NO8 p12. ==== Montagnais Crater Impact, 51M BCE ==== Formed on the continental shelf off Novia Scotia, Canada, this crater is currently buried beneath marine sediments and the sea. [[http://en.wikipedia.org/wiki/Montagnais_crater]] ==== PETM (Paleocene-Eocene Thermal Maximum), 55M BCE ==== Earth's CO2 levels shot up to 1700PPM (compared to 401ppm, as of 13OCT2016), and the Arctic Ocean was no colder than a luke-warm bath at around 73F; earth's overall temperature rose between 5 and 9 degrees Centigrade in just a few thousand years. The current assumption is that the CO2 levels were introduced both volcanically, and through the release of methane from the sea floor as methylated hydrates melted. More recent evidence indicates that this and other 'hyperthermals' took place every 400k years. There is, however, strong evidence for an extraterrestrial impact during this time, as well. [[http://www.physorg.com/news166715232.html]]\\ [[http://www.physorg.com/news/2011-03-ancient-hyperthermals-climate.html]] - Hyperthermals\\ [[http://phys.org/news/2016-10-jersey-shore-comet-climate-crisis.html]] -- Impact\\ This rise in temperature likely drove out much of the oxygen in the world's oceans, causing a large die off of marine animals. The world would have shifted to a warmer and wetter overall climate, a major selection event in and of itself. ==== Hiawatha Crater, 58M BCE ==== Originally thought to be only 13,000 years old, later analyses indicate that Hiawatha Crater on Greenland is much, much older. [[https://phys.org/news/2022-03-giant-impact-crater-greenland-million.html]]\\ ==== K-T Boundary, 65M BCE ==== Himalayan orogeny begins; Deccan Flats form, altering global atmospheric conditions as they sop up oxygen; Yucatan impact occurs. Recent evidence suggests that toxic algae may have been responsible for the deaths of the dinosaurs. As well, a massive crater west of the Deccan Flats at roughly the same timeframe as the Yucatan impact, may mean that multiple bolides struck the earth at the KT boundary. The equivalent yield has been estimated at some 250,000,000 megatons of TNT (see La Garita Caldera Wikipedia entry). Dr Gerta Keller published one of the most detailed analyses of the time, indicating multiple impacts scattered over hundreds of thousands of years -- and also indicating that the impacts were not the source of the extinctions, at least individually. [[http://www.physorg.com/news174827113.html]] - Indian Hammer\\ [[http://www.physorg.com/news175179438.html]] - Killer Algae\\ [[http://en.wikipedia.org/wiki/K-t_boundary]]\\ [[http://www.physorg.com/news202449869.html]] - Boltysh Crater\\ [[http://www.physorg.com/news160655449.html]] - Gerta Keller Analysis Reference\\ ==== Sakamoto Point, 90M BCE ==== Dinosaur extinction rates approach the speciation rate, signalling the decline of the dinosaurs. The sauropods had the largest decline among the three main dinosaur types [[http://www.foxnews.com/science/2016/04/22/dinosaur-decline-started-long-before-asteroid-impact.html?intcmp=hpff]] ==== Bonarelli Event, 93M BCE ==== Mass underwater vulcanism causes near global anoxic ocean conditions, wiping out much of life in the seas and creating the shale / petroleum deposits we access today for oil. This roughly corresponds to the beginning of the Turonian Stage. [[http://en.wikipedia.org/wiki/Turonian]]\\ ==== Paraná and Etendeka Traps, 134M BCE ==== Some debate that these Brazilian-Namibian volcanoes may have been the largest volcanic eruptions in earth's history, due to the breakup of South America and Africa beginning. [[http://en.wikipedia.org/wiki/Paran%C3%A1_and_Etendeka_traps]] ==== Indian Ocean Opens, 145M BCE ==== Indian Ocean begins to open, and coincides roughly with an impact cluster. [[http://phys.org/news/2013-03-link-co2-mass-extinctions-species.html]] ==== Triassic-Jurassic Extinction, 200M BCE ==== Seventy-six percent of all species go extinct, as Pangaea breaks up with accompanying changes in vulcanism, sea-level change, and altered climate. Asteroid or comet impacts have also been implicated in the mass extinctions. This event allowed for the real rise of the dinosaurs to dominant status. At least one author believes that the low oxygen levels of the time, coupled with high carbon dioxide levels and hydrogen sulfide poisoning, may have been the underlying cause of the extinction. [[http://www.nap.edu/openbook.php?record_id=11630&page=204]]\\ [[http://en.wikipedia.org/wiki/Pangaea]]\\ ==== Manicouagan Crater Forms, 215.5M BCE ==== This massive impact structure, 100km wide, is easily visible from space -- and is the 5th largest confirmed impact crater on earth. Located near Quebec, Canada, it has an inner island that gives it the appearance of a giant eye as seen from orbit. [[http://en.wikipedia.org/wiki/Manicouagan_impact_crater]] ==== Carnian Pluvial Event, 230M BCE ==== Wrangellian eruptions over five million years inject carbon dioxide into the atmosphere, acififying the oceans and contributing to a two million year long flooding period that changed the land from hot and dry to hot and wet. Plant growth on land erupted, changing the ecological support, and leaving only the dinosaurs best suited to eat and digest the woodier plant matter. [[https://en.wikipedia.org/wiki/Carnian_Pluvial_Event]] ==== Permian-Triassic Extinction, 252M BCE ==== Permian-Triassic extinction event, cause unknown; greatest mass extinction of life ever recorded: 96% of all marine sp, and 70% of all terrestrial sp go extinct. Suspected causes of the mass extinction include the formation of the Siberian Traps, a string of volcanoes that erupted for 5 million years. One theory holds that any super-continent that forms stops subduction events along plate margins until a massive pressure release occurs. The massive release carried with it enough sulfur to acidify the rain to a pH of 2. This extinction event marks the end of the trilobites and the rise of the bivalves, which may have occurred due to invasive species that could not be isolated by geography. [[http://en.wikipedia.org/wiki/Permian-Triassic_extinction_event]]\\ [[http://www.physorg.com/news/2010-12-triggers-mass-extinctions-invasive-species.html]]\\ [[http://web.mit.edu/press/2013/permian-acid-rain-extinction.html]]\\ In one case, the Siberian Traps' formation seems to allude to modern cancer rates in one region of China, where the P-T coal of the region was altered by the long-term vulcanism 250M years ago. Interestingly enough, these coal beds existed at the time of the P-T extinction, and are implicated as a 'smoking gun' in the extinction of most life forms: massive vulcanism coupled with local extant coal beds led to off-the-scale coal burning and volcanic pollution. [[http://www.physorg.com/news182600452.html]] - Chinese cancers due to ancient coal beds\\ [[http://www.physorg.com/news/2011-01-gun-world-biggest-extinction.html]] - smoking gun\\ [[http://www.physorg.com/news/2012-02-global-extinction-gradual-doom-bad.html]]\\ Prior to the PT extinction, global oxygen levels were at their highest known levels of some 31% atmospheric O2. After the PT extinction (over the course of ten million years or so), the atmospheric O2 levels dropped to some 16% before attempting and failing a rebound that further dropped. In the early Triassic, the O2 level stayed at roughly 12-14% before climbing back up during the Cretaceous. One reason for the low oxygen levels may have been CO2-acidified rain freeing nutrients from land masses, leading to massive algal blooms and eutrophying global oceans; this, in turn, would have kept the oceans anoxic for a longer time. [[http://www.nap.edu/openbook.php?record_id=11630&page=38]]. Peter D Ward. 2006. //Out of thin air: Dinosaurs, birds, and earth's ancient atmosphere.// Joseph Henry Press.\\ [[http://www.physorg.com/news/2011-03-algae-bacteria-hogged-oxygen-ancient.html]]\\ There are some indications that there were impact events during this time, as well. [[http://phys.org/news/2013-03-link-co2-mass-extinctions-species.html]] ==== End-Capitanian Extinction Event, 260M BCE ==== Global anoxia caused by Emeishan Traps in China. [[http://en.wikipedia.org/wiki/Emeishan_Traps]]\\ [[http://phys.org/news/2015-04-evidence-capitanian-extinction-major-crises.html]]\\ ==== Carboniferous End, 300M BCE ==== A fungus known as 'white rot' develops the ability to break down lignin -- ending the Carboniferous Period and ending much of the coal deposition around the world. [[http://phys.org/news/2012-06-fungi-coal-formation-advance-future.html]] ==== KGB Carbon Dioxide Jump, 304M BCE ==== Kasimovian-Gzhelian boundary (KGB) records doubling in CO2 from 350ppm to 700ppm within just 300,000 years. [[https://phys.org/news/2022-05-carbon-climate-ocean-anoxia-ancient.html]]\\ ==== End Devonian Impacts, Karoo Glaciation, 360M BCE ==== Impact cluster and peak warming, followed by a major glaciation event. The Mississipian Period ice age is thought to be more related to global ocean currents changing than to the impacts and lasted 40 million years, and was followed by a Pennsylvanian Period ice age that lasted another 20 million years. [[http://phys.org/news/2013-03-link-co2-mass-extinctions-species.html]] [[http://en.wikipedia.org/wiki/Karoo_Ice_Age]] ==== Late Devonian Extinction, 376M BCE ==== Over 70% of all species go extinct as ocean oxygen levels plummet, as global cooling causes massive ice sheets to form. Suspected causes include vulcanism and asteroid or comet impacts. The big armored fish commonly seen in museums finally died out during this event, and paved the way for the ancestral vertebrate fish to move onto land. The event can be broken up into two separate extinctions over some 15M years: the Kellwasser and the Hangenberg Events. There is the potential that the extinctions were caused by a gamma ray burst. [[http://en.wikipedia.org/wiki/Late_Devonian_extinction]]\\ [[http://www.sciencedaily.com/releases/2010/05/100517152518.htm]]\\ Piran T and Jimenez R, 05DEC2014. Possible Role of Gamma Ray Bursts on Life Extinction in the Universe Phys. Rev. Lett. 113, 231102.\\ ==== Late Ordovician Extinction, 443M BCE ==== Located in England, the Scafell Eruption (VEI 8) took place at the end of the Ordovician, when some 85% of all life on earth went extinct with a rapid advance and retreat of glaciers. How much Scafell affected the glacial advance and retreat is currently unknown, as Gondwana was also drifting over the South Pole at that time, forming ice caps and sequestering global water. A supernova has been fingered as a potential culprit, as well. [[http://en.wikipedia.org/wiki/Scafells]]\\ Birkett, B. 2007. __Scafell, Portrait of a Mountain__ London: Frances Lincoln Limited. p12\\ [[http://en.wikipedia.org/wiki/Ordovician]]\\ [[https://en.wikipedia.org/wiki/Ordovician%E2%80%93Silurian_extinction_events]]\\ [[https://en.wikipedia.org/wiki/Ordovician%E2%80%93Silurian_extinction_events]]\\ [[https://en.wikipedia.org/wiki/Near-Earth_supernova]]\\ ==== Andean-Saharan Glaciation, 450M BCE ==== A 30 million year glaciation occurred during the Ordovician Period, which some think may be linked to colonization of land by plants around 470M BCE. [[http://en.wikipedia.org/wiki/Andean-Saharan_glaciation]]\\ [[https://www.newscientist.com/article/dn21417-first-land-plants-plunged-earth-into-ice-age/]]\\ ==== Jamtland Event Craters, 460M BCE ==== Two asteroids apparently smashed into one another in the belt, sending off a myriad of pieces that slammed into earth over the next several million years. Ten million years' worth of impacts around this time frame may be related. This also marks the first time a double impact has been proven beyond a shadow of a doubt. [[http://www.gu.se/english/about_the_university/news-calendar/News_detail//globally-unique-double-crater-identified-in-sweden.cid1317063#prettyPhoto]] ==== Decorah Crater and Glen Coe, 470M BCE ==== A " 'nice circular basin' of 5.5 km width, according to Robert McKay" (Ann Khan) forms near Decorah, Iowa. The impact may have been one of several, as others in North America seem to date from the same time period. [[http://blog.lib.uiowa.edu/eng/iowa-meteorite-crater-confirmed/]]\\ [[http://www.earthmagazine.org/article/iowa-impact-crater-confirmed]]\\ Located in the Scottish Highlands, this VEI 8 last erupted in the Silurian, and has long since been ground down by glaciers. [[http://en.wikipedia.org/wiki/Glen_Coe]]\\ This time frame also marks the first plants on land. ==== Oxygen Yo-Yo, 499M BCE ==== The oxygenated atmosphere suffered a drastic reduction in oxygen for several million years, precipitating a yo-yo effect of oxygenation and deoxygenation for some tens of millions of years. Eventually, a relatively stable oxygen atmosphere developed, but not before going through several periods of anoxia. This general period roughly corresponds to the Cambrian Explosion, in which life experimented with many shapes and many forms. This oxygen yo-yo effect appears to have been the main selection mechanism for life as we know it. [[http://www.physorg.com/news/2011-01-oxygen-early-life.html]]\\ [[http://en.wikipedia.org/wiki/Cambrian_explosion]]\\ [[http://www.physorg.com/news/2011-02-oldest-fossils-large-seaweeds-worm-like.html]] - 600M BCE oxic conditions\\ ==== Acraman Crater Impact, 580M BCE ==== Found in southern Australia, the crater is currently a playa lake about 20km in diameter, though the original crater may have been up to 90km wide. The event is believed to have been the equivalent of 5.2 terratons of TNT. [[http://en.wikipedia.org/wiki/Acraman_crater]] ==== Marinoan / Varangian Glaciation, 635M BCE ==== Snowball earth very nearly became permanent -- and many multicellular animals died out in the near global glaciation. In addition to suspected global extinctions, the glaciation most likely scoured much of the world clean of prior fossils. The earliest known multicellular fossils, believed to be sponge-like, date from this time frame. [[http://www.sciencedaily.com/releases/2010/08/100817144641.htm]]\\ [[http://en.wikipedia.org/wiki/Marinoan]]\\ ==== Sturtian Glaciation, 700M BCE ==== The first of the major known glaciations in the Cryogenian Period, the Sturtian Glaciation lasted over 30M years. The formation of massive continental shelves, coupled with limestone formation, may have played a part in the glaciation. [[http://en.wikipedia.org/wiki/Cryogenian]]\\ ==== Rodinia Supercontinent, 750M BCE ==== Fourth supercontinent breaks up. [[http://en.wikipedia.org/wiki/Supercontinent]]\\ [[http://www.enotes.com/earth-science/supercontinents]]\\