Precambrian Eon
4.6 - 541 M 4.059
Archean Eon
4 - 2.5 1.5
Mesoarchaean
 3.2 - 2.8 400M
| 3 Life on Earth began to become more complex, with the emergence of single-celled organisms. These early life forms were primarily prokaryotes (cells without a nucleus), including bacteria and archaea. This period is often referred to as the Archean Eon. |
| 3 Cyanobacteria, also known as blue-green algae, evolved around this time and began photosynthesizing. This process released oxygen as a byproduct, which eventually contributed to the Great Oxidation Event. |
| 3 evolution of oxygenic photosynthesis by cyanobacteria marked a major turning point in Earth's history. These organisms used sunlight to convert carbon dioxide and water into glucose, releasing oxygen. This oxygen slowly accumulated in the atmosphere, setting the stage for the eventual rise of aerobic (oxygen-dependent) life forms. |
| 3 During this time, Earth’s crust began to stabilize and form more distinct continental landmasses. These landmasses were small but began to grow and shape the geological structure of the planet. |
| 3 Earth's atmosphere at this time was still largely anoxic (lacking oxygen) but started to undergo changes due to the release of oxygen by early photosynthetic organisms. The oceans were rich in minerals and chemicals, setting the stage for more complex biochemical processes. |
| 3  Earth's magnetic field was likely already in place. This field protects the Earth from harmful solar radiation and played a crucial role in creating a stable environment conducive to life. |
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Neoarchean
 2.8 - 2.5 .3 |
| Earth's permanent crust is formed. Vast amounts of metallic minerals are deposited. oceans & atmosphere result from volcanic outgassing. |
prokaryotes earliest life in seas. single cell no nucleus
cyanobacteria (blue-green algae). earliest bacteria obtain energy through chemosynthesis (ingestion of organic molecules). |
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Proterozoic Eon
2.5 - 541 M 2,047,000,000
Paleoproterozoic Era
 2.5 - 1.6 1B
Siderian 2.5 - 2.3 .2
| 2.5 First organisms to utilize oxygen. |
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Precambrian Eon
4.6 - 541 M 4.059
Proterozoic Eon
2.5 - 541 M 2,047,000,000
Paleoproterozoic Era
 2.5 - 1.6 1B
Orosirian
2.05-1.8 2.05
| 2 Complex cells appear: Eukaryotes, which contain various organelles. eukaryotic cell seems to have evolved from a symbiotic community of prokaryotic cells. origin of eukaryotic cell is a milestone in evolution of life. Their higher level of organizational complexity permits development of truly multicellular organisms. |
| 2 oxygen levels in Earth's atmosphere began to rise significantly during this period. The rise in atmospheric oxygen was primarily caused by photosynthetic microorganisms, like cyanobacteria, that began producing oxygen as a byproduct. This event fundamentally changed the planet's atmosphere and made Earth more hospitable to aerobic (oxygen-breathing) organisms. |
| 2 supercontinent known as Columbia (or Nuna) existed during this time. It began to break apart, setting the stage for the formation of future continents. The breakup of supercontinents has been a repeating process throughout Earth's history, driving geological and biological evolution. |
| 2 Earth’s oceans were rich in life forms, especially microbial life. The development of photosynthesis by cyanobacteria played a key role in altering the planet’s carbon and oxygen cycles. |
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 Statherian Period
 1.8 - 1.6 200M |
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Precambrian Eon
4.6 - 541 M 4.059
Proterozoic Eon
2.5 - 541 M 2,047,000,000
Paleoproterozoic EraÂ
2.5 - 1.6 1B
 Statherian Period
 1.8 - 1.6 200M |
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Mesoproterozoic Era
1.6 B - 1B .6
Calymmian
 1.6 - 1.4 200M |
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Precambrian Eon
4.6 - 541 M 4.059
Proterozoic Eon
2.5 - 541 M 2,047,000,000
Mesoproterozoic Era
1.6 B - 1B .6
1.1 Rodinia Supercontinent Plate tectonics slows to present. mountain form as continents collide. Quartz sandstones, shales, limestones deposited Oxygen increase life obtain energy photosynthesis. late Proterozoic is an "Ice House" world.
1.1 Eukaryotes single-celled organisms with nucleus more advanced algae & variety of protozoa. reproduce sexually, genetic diversity adapt & survive environment
metazoans Multi-celled soft-bodied marine |
| 1.2 Sexual reproduction evolves, leading to faster evolution. |
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Neoproterozoic Era
1B - 541
TonianÂ
1B - 720Â 280
| 1 Earth's tectonic plates were still moving, and a supercontinent called Columbia (sometimes referred to as Nuna) existed. Columbia began to break apart around this time, and the process of continental drift was actively shaping the planet's landmasses. |
| 1 Life on Earth was predominantly microbial. Cyanobacteria, which were already producing oxygen through photosynthesis, were thriving and contributing to the gradual buildup of oxygen in the atmosphere—a process that would eventually lead to the Great Oxidation Event (about 2.4 billion years ago). |
| 1 Earth's atmosphere still had relatively low levels of oxygen. It wasn't until much later, through processes like photosynthesis by microorganisms, that oxygen levels began to rise significantly, leading to the conditions we have today. |
| 1 oceans were teeming with microorganisms, including early forms of algae and bacteria, but complex life forms had not yet evolved. There was no evidence of multicellular life forms yet, and most organisms were microscopic. |
| 1 Earth's surface was much hotter than today, and volcanic activity was high. The planet's crust was still cooling, and the landscape was dominated by a very different climate compared to today's conditions. |
900 - 543 Neoproterozoic
900 Choanoflagellates ancestors animals, & in particular sponges.
| 850 Proterospongia best living examples ancestor of all animals |
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650 - 543 Vendian Sub-period.
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Precambrian Eon
4.6 - 541 M 4.059
Proterozoic Eon
2.5 - 541 M 2,047,000,000
Neoproterozoic Era
1B - 541
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Phanerozoic Eon
541 - Present
Paleozoic Era (Ancient Life)
543 - 248 295 |
Cambrian Period
541 - 485.4 55.6
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Ordovician Period
485.4 - 443.8 41.6
Early Ordovician
0 - 0 0
Tremadocian Stage
0 - 0 0 |
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Middle Ordovician
0 - 0 0
Darriwilian Stage
0 - 0 0 |
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 Silurian Period
443.8 - 419.2 24.6
Cayugan (Late Silurian – Ludlow)
| Lockportian  (Middle Silurian: late Wenlock) |
| Tonawandan  (Middle Silurian: early Wenlock) |
| Ontarian (Early Silurian: late Llandovery) |
| In Estonia the following suite of regional stages is used: |
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 Devonian
419.2 - 358.9 60.3
Lower Devonian
419.2 - 393.3 0
Lochkovian Stage
419.2 - 410.8 0 |
Pragian Stage
410.8 - 407.6 0 |
Emsian Stage
407.6 - 393.3 0 |
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Carboniferous
358.9 - 298.9 60
Mississippian Stage
382.7 - 372.2 0
Tournaisian Stage
419.2 - 410.8 0 |
Visean Stage
410.8 - 407.6 0 |
Serpukhovian Stage
407.6 - 393.3 0 |
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Permian
298.9 - 251.9 47
Cisuralian Stage
298.9 - 272.95 0
Asselian Stage
298.9 - 295 0 |
Sakmarian Stage
295 - 290.1 0 |
Artinskian Stage
290.1 - 283.5 0 |
Kungurian Stage
283.5 - 272.95 0 |
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Guadalupian Stage
272.95 - 259.1 0
Capitanian
265.1 - 259.1 0 |
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Lopingian Stage
259.1 - 251.902 0
Wuchiapingian Stage
259.1 - 254.14 0 |
Changhsingian
254.14 - 251.902 0 |
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543 - Present Phanerozoic Era
| 500 Fish and Proto-amphibians |
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251.902 - 66 Mesozoic Era (Middle Life)
250 Million to present 1st Galactic year
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Carboniferous Period 354 - 290
Geologic - Sedimentary rocks (sandstone, shale, limestone, conglomerate) form in shallow seas over continents. Rodinia begins to break up into northern & southern portions. Gondwana in south incorporates South America, Africa, Antarctica, & Western Australia as well as peninsular India & parts of Arabia.
global climate is generally mild.
Biologic - The first fish, corals, and shellfish appeared.
Marine metazoans with mineralized skeletons, such as sponges, bryozoans, corals, brachiopods, molluscs, arthropods, and echinoderms, flourish. One group of arthropods, trilobites, are particularly dominant in shallow-water marine habitats.
Plant life is limited to marine algae.
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65 - Present Cenozoic Era
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| 600 It is thought that earliest multicellular life on Earth was a sponge-like creature. |
| Sponges are among simplest of animals, with partially differentiated tissues but without muscles, nerves, or internal organs. Porifera are phylogenetically oldest animal phylum extant today. In some ways they are closer to being cell colonies than multicellular organisms. |
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