Timeline of Earth

Dating of the geologic record

The earliest Solar System

• c. 4,570 Ma – A supernova explosion seeds our galactic neighborhood with heavy elements that will be incorporated into the Earth, and results in a shock wave in a dense region of the Milky Way galaxy. The Ca-Al-rich inclusions, which formed 2 million years before the chondrules, are a key signature of a supernova explosion.
• c. 4,567 ±3 Ma – Rapid collapse of hydrogen molecular cloud, forming a third-generation Population I star, the Sun, in a region of the Galactic Habitable Zone, about 25,000 light years from the center of the Milky Way Galaxy.
• c. 4,566 ±2 Ma – A protoplanetary disc emerges around the young Sun, which is in its T Tauri stage.
• c. 4,560–4,550 Ma – Proto-Earth forms at the outer edge of the habitable zone of the Solar System. At this stage the solar constant of the Sun was only about 73% of its current value, but liquid water may have existed on the surface of the Proto-Earth, probably due to the greenhouse warming of high levels of methane and carbon dioxide present in the atmosphere. Early bombardment phase begins: because the solar neighbourhood is rife with large planetoids and debris, Earth experiences a number of giant impacts that help to increase its overall size.

  Precambrian Supereon

• c. 4,533 Ma – The Precambrian, now termed a "supereon" but formerly an era, is split into three geological time intervals called eons: Hadean, Archaean and Proterozoic. The latter two are sub-divided into several eras as currently defined. In total, the Precambrian comprises some 85% of geological time from the formation of Earth to the time when creatures first developed exoskeletons and thereby left abundant fossil remains.

  Hadean Eon

• c. 4,533 Ma – Hadean Eon, Precambrian Supereon and unofficial Cryptic era start as the Earth–Moon system forms, possibly as a result of a glancing collision between proto-Earth and the hypothetical protoplanet Theia. This impact vaporized a large amount of the crust, and sent material into orbit around Earth, which lingered as rings, similar to those of Saturn, for a few million years, until they coalesced to become the Moon. The Moon geology pre-Nectarian period starts. Earth was covered by a magmatic ocean deep resulting from the impact energy from this and other planetesimals during the early bombardment phase, and energy released by the planetary core forming. Outgassing from crustal rocks gives Earth a reducing atmosphere of methane, nitrogen, hydrogen, ammonia, and water vapour, with lesser amounts of hydrogen sulfide, carbon monoxide, then carbon dioxide. With further full outgassing over 1000–1500 K, nitrogen and ammonia become lesser constituents, and comparable amounts of methane, carbon monoxide, carbon dioxide, water vapour, and hydrogen are released.
• c. 4,500 Ma – Sun enters main sequence: a solar wind sweeps the Earth-Moon system clear of debris. End of the Early Bombardment Phase. Basin Groups Era begins on Earth.
• c. 4,450 Ma – 100 million years after the Moon formed, the first lunar crust, formed of lunar anorthosite, differentiates from lower magmas. The earliest Earth crust probably forms similarly out of similar material. On Earth the pluvial period starts, in which the Earth's crust cools enough to let oceans form.
• c. 4,404 Ma – First known mineral, found at Jack Hills in Western Australia. Detrital zircons show presence of a solid crust and liquid water. Latest possible date for a secondary atmosphere to form, produced by the Earth's crust outgassing, reinforced by water and possibly organic molecules delivered by comet impacts and carbonaceous chondrites.
• c. 4,300 Ma – Nectarian Era begins on Earth.
• c. 4,250 Ma – Earliest evidence for life, based on unusually high amounts of light isotopes of carbon, a common sign of life, found in Earth's oldest mineral deposits located in the Jack Hills of Western Australia.
• c. 4,100 Ma – Early Imbrian Era begins on Earth. Late heavy bombardment of the Moon by bolides and asteroids, produced possibly by the planetary migration of Neptune into the Kuiper belt as a result of orbital resonances between Jupiter and Saturn. "Remains of biotic life" were found in 4.1 billion-year-old rocks in Western Australia. According to one of the researchers, "If life arose relatively quickly on Earth... then it could be common in the universe."

  Archean Eon

Eoarchean Era

• c. 4,031 Ma – Archean Eon and Eoarchean Era start. Possible first appearance of plate tectonic activity in the Earth's crust as plate structures may have begun appearing. Possible beginning of Napier Mountains Orogeny forces of faulting and folding create first metamorphic rocks. Origins of life.
• c. 4,030 Ma – Acasta Gneiss of Northwest Territories, Canada, first known oldest rock, or aggregate of minerals.
• c. 3,930 Ma – Possible stabilization of Canadian Shield begins
• c. 3,920–3,850 Ma – Final phase of Late Heavy Bombardment
• c. 3,850 Ma – Greenland apatite shows evidence of ¹²C enrichment, characteristic of the presence of photosynthetic life.
• c. 3,850 Ma – Evidence of life: Akilia Island graphite off Western Greenland contains evidence of kerogen, of a type consistent with photosynthesis.
• c. 3,800 Ma – Oldest banded iron formations found. First complete continental masses or cratons, formed of granite blocks, appear on Earth. Occurrence of initial felsic igneous activity on eastern edge of Antarctic craton as first great continental mass begins to coalesce. East European Craton begins to formfirst rocks of the Ukrainian Shield and Voronezh Massif are laid down
• c. 3,750 Ma – Nuvvuagittuq Greenstone Belt forms
• c. 3,700 Ma – Graphite found to be biogenic in 3.7 billion-year-old metasedimentary rocks discovered in Western Greenland Stabilization of Kaapval craton begins: old tonaltic gneisses laid down

  Paleoarchean Era

• c. 3,600 Ma – Paleoarchean Era starts. Possible assembly of the Vaalbara supercontinent; oldest cratons on Earth begin growing as a result of crustal disturbances along continents coalescing into VaalbaraPilbara Craton stabilizes. Formation of Barberton greenstone belt: Makhonjwa Mountains uplifts on the eastern edge of Kaapval craton, oldest mountains in Africaarea called the "genesis of life" for exceptional preservation of fossils. Narryer gneiss terrane stabilizes: these gneisses become the "bedrock" for the formation of the Yilgarn craton in Australianoted for the survival of the Jack Hills where the oldest mineral, a zircon was uncovered.
• c. 3,500 Ma – Lifetime of the Last universal ancestor: split between bacteria and archaea occurs as "tree of life" begins branching outvarieties of Eubacteria begin to radiate out globally. Fossils resembling cyanobacteria, found at Warrawoona, Western Australia.
• c. 3,480 Ma – Fossils of microbial mat found in 3.48 billion-year-old sandstone discovered in Western Australia. First appearance of stromatolitic organisms that grow at interfaces between different types of material, mostly on submerged or moist surfaces.
• c. 3,460 Ma – Fossils of bacteria in chert. Zimbabwe Craton stabilizes from the suture of two smaller crustal blocks, the Tokwe Segment to the south and the Rhodesdale Segment or Rhodesdale gneiss to the north.
• c. 3.400 Ma – Eleven taxa of prokaryotes are preserved in the Apex Chert of the Pilbara craton in Australia. Because chert is fine-grained silica-rich microcrystalline, cryptocrystalline or microfibrious material, it preserves small fossils quite well. Stabilization of Baltic Shield begins.
• c. 3.340 Ma – Johannesburg Dome forms in South Africa: located in the central part of Kaapvaal craton and consists of trondhjemitic and tonalitic granitic rocks intruded into mafic-ultramafic greenstonethe oldest granitoid phase recognised so far.
• c. 3,300 Ma – Onset of compressional tectonics. Intrusion of granitic plutons on the Kaapvaal craton.
• c. 3,260 Ma – One of the largest recorded impact events occurs near the Barberton Greenstone Belt, when a 58 km asteroid leaves a crater almost 480 km across - two and a half times larger in diameter than the Chicxulub crater.