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====== Billions of Years BCE Events ======

Before Common Era (BCE) events more than a billion years ago.

==== Columbia Supercontinent, 1.5B BCE ====

Third supercontinent breaks up.

[[http://www.enotes.com/earth-science/supercontinents]]\\
[[http://en.wikipedia.org/wiki/Supercontinent]]\\

Upper bound for the development of nitrogen fixation.  It could have begun 2.2 BCE up to 1.5B BCE, and likely was only possible because of the GOE.

[[http://www.physorg.com/news/2011-06-team-discoveries-major-event-history.html]]

==== Sudbury Basin Impact, 1.849B BCE ====

A bolide approximately 15km wide hit near Ontario, Canada.  The basin is some 62km long and 30km wide (and 15km deep).  The original basin is believed to have been some 250km wide, though erosion has since filled in much of the crater.  This date ties in with the end of the Late Heavy Bombardment that began 4.1B years ago, and apparently continued until about 1.8B BCE according to newer estimates.

[[http://en.wikipedia.org/wiki/Sudbury_Basin]]
Nadia Drake.  2012.  Earth's beating lasted longer:  Bombardment persisted over 2 billion years, analysis finds.  //Science News//.  Vol181(11), p8.

==== Vredefort Crater Impact, 2.023B BCE ====

The largest confirmed impact crater on earth is the Vredefort impact structure in South Africa.  The asteroid that hit is estimated to be up to 10km wide, and it created a crater some 300km wide.  It is one of the few multi-ringed impact craters on earth, and is a UNESCO World Heritage Site.  The impact is responsible for some of the world's richest gold deposits.

[[http://en.wikipedia.org/wiki/Vredefort_crater]]\\
[[https://en.wikipedia.org/wiki/Witwatersrand_Basin]]

==== Huronian Glaciation, 2.4 BCE ====

The first and longest known glaciation took place not long after the GOE.  As atmospheric oxygen increased, atmospheric carbon dioxide (a greenhouse gas) decreased -- and brought plunging global temperatures.  The Huronian lasted some 300 million years, and may have nearly caused a Snowball Earth catastrophe in its own right.

[[http://en.wikipedia.org/wiki/Huronian_glaciation]]

==== Global Oxidation Event (GOE) 2.33B BCE ====

Oxygen is a highly corrosive gas that the first forms of life on earth found very poisonous -- and yet we need it to survive.  It's formation may not have been as rapid as geologists once thought, but it is still a significant event in earth's history, when the atmosphere reached oxygen percentages much like that of today's.  It culminated with the evolution of the electron transport chain, a key step in the evolution of eukaryotic life.

[[http://www.physorg.com/news/2010-12-scientists-decipher-billion-year-old-genomic-fossils.html]]\\
[[http://www.physorg.com/news176044643.html]]\\
[[http://phys.org/news/2016-05-oxygen-earth-atmosphere.html]]\\
[[https://phys.org/news/2017-11-met-iron-deep-earth-conditions.html]]\\

==== Kenorland Supercontinent, 2.6B BCE ====

Second supercontinent breaks up.

[[http://en.wikipedia.org/wiki/Supercontinent]]\\
[[http://www.enotes.com/earth-science/supercontinents]]\\

==== Vaalbara Supercontinent Breaks Up, 2.8B BCE ====

[[https://en.wikipedia.org/wiki/Mesoarchean]]\\

==== Pongola Glaciation, 2.9B BCE ====

Major global glaciation event occurs.

[[https://en.wikipedia.org/wiki/Mesoarchean]]\\

==== Maniitsoq Impact, 3B BCE ====

Massive impact  shocks the rock deep beneath the initial formation, such that only the shock indicators remain some three billion years later.

[[http://phys.org/news/2012-06-earth-oldest-impact-crater-greenland.html]]

==== Vaalbara (Ur) Supercontinent, 3.2B BCE ====

Theorized first supercontinent completes its formation.  Analysis of diamond inclusions indicates that the first continental subductions began at this time.  Vaalbara is sometimes referred to in the literature as Ur, due to imperfections in calculations going back that far.

[[http://en.wikipedia.org/wiki/Vaalbara]]\\
[[http://www.enotes.com/earth-science/supercontinents]]\\
[[http://carnegiescience.edu/news/copies_paper_contact_scipakaaasorg_diamonds_pinpoint_start_colliding_continents]]\\

==== Barberton Impact, 3.2B BCE ====

A 40km wide impactor hit the earth at 20km/s, gouging out a crater 500km across and punching into the mantle.  The impact may have sparked modern plate tectonics in the region.

[[http://phys.org/news/2014-04-scientists-reconstruct-ancient-impact-dwarfs.html]]\\

==== Hadean Bombardment, 4B BCE ====

The heavy cratering of earth during the Hadean knocked away much of the chlorine and other halogens.  With the chlorine levels knocked down to a tenth of pre-bombardment levels, the salt content of the oceans was prevented from becoming like that of the Dead Sea -- or saltier.  The cometary impacts also brought water-ice for the oceans to form, as well as complex carbon molecules.  The comets may even have synthesized the first complex carbon chains.

[[http://phys.org/news/2013-06-life-earth-shockingly-world.html]]
[[http://phys.org/news/2013-05-massive-impacts-dispersed-chlorine-earth.html]]
[[http://en.wikipedia.org/wiki/Hadean]]

==== Theian Bombardment, 4.5B BCE ====

A Mars-sized object named Theia slams into earth, lending its metallic core to our own and giving us our magnetic field to protect us from solar radiation.  Theia's mantle and part of our own became a ring, and then our moon, whose gravitational influence created the lunar cycle.

[[http://en.wikipedia.org/wiki/Theia_%28planet%29#Theia]]
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