Astronomical and geological evidence indicates that the Universe is approximately 13,700 million years old, and our solar system is about 4,567 million years old. Earth's Moon formed 4,450 million years ago, just 50 million years after the Earth's formation. Because the composition of the rocks retrieved from the Moon by the Apollo missions is very similar to rocks from the Earth, it is thought that the Moon formed as a result of a collision between the young Earth and a Mars-sized body, sometimes called Orpheus or Theia, which accreted at a Lagrangian point 60° ahead or behind the Earth. A cataclysmic meteorite bombardment of the Moon and the Earth 3,900 million years ago is thought to have been caused by the debris of a planetary collision beyond the earth or by asteroids whose orbits were destabilized and were sent toward the inner solar system during the formation of planets beyond the Earth. The Mars Reconnaissance Orbiter and the Mars Global Surveyor have found evidence that the Borealis basin in the northern hemisphere of Mars may have been created by a colossal impact with an object 2,000 kilometers in diameter approximately 3,900 million years ago. The debris from this impact could have been responsible for the cataclysmic meteorite bombardment of the Earth and the Moon.
Approximately 3,000 million years ago, the earth was cool enough for land masses to form. The supercontinent Rodinia was formed about 1100 million years ago, and it broke into several pieces that drifted apart 750 million years ago. Those pieces came back together about 600 million years ago, forming the Pan-African mountains in a new supercontinent called Pannotia. Pannotia started breaking up 550 million years ago to form Laurasia and Gondwana. Laurasia included what are now North America, Europe, Siberia, and Greenland. Gondwana included what is now India, Africa, South America, and Antarctica. Laurasia and Gondwana rejoined approximately 275 million years ago to form the supercontinent of Pangea. The break up of Pangea, which still goes on today, has contributed to the formation of the Atlantic Ocean.
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(mya = million years ago)The times are approximate and may vary by a few million years.
Hadean Eon (3800 mya and earlier)
- 4567 mya: Formation of the Solar System Sun was only 70% as bright as today.
- 4450 mya: Earth's collision with a planetoid forms the moon.
- Earth's original hydrogen and helium atmosphere escapes Earth's gravity.
- Earth day is 6 hours long - 3900 mya: Cataclysmic meteorite bombardment.
- Earth's atmosphere becomes mostly carbon dioxide, water vapor, methane, and ammonia.
- Formation of carbonate minerals starts depleting atmospheric carbon dioxide.
- There is no geologic record for the Hadean Eon.
Archaean Eon (3800 to 2500 mya)
- 3800 mya: Surface of the Earth changed from molten to solid rock.
- Water started condensing in liquid form. - Earth day is 15 hours long
- 3500 mya: Monocellular life started (Prokaryotes). First known oxygen-producing bacteria:cyanobacteria (blue-green algae) form stromatolites
- 3000 mya: Atmosphere has 75% nitrogen, 15% carbon dioxide.
- Sun brightens to 80% of current level. - Oldest record of Earth's magnetic field.
Proterozoic Eon (2500 to 542 mya)
Paleoproterozoic Era (2500 to 1600 mya)
Siderian Period (2500 to 2300 mya)
- Stable continents first appeared.
- 2500 mya: First free oxygen is found in the oceans and atmosphere.
- 2400 mya: Great Oxidation Event, also called the Oxygen Catastrophe. Oxidation precipitates dissolved iron creating banded iron formations. Anaerobic organisms are poisoned by oxygen.
- 2400 mya: Start of Huronian ice age
Rhyacian Period (2300 to 2050 mya)
- 2200 mya: Organisms with mitochondria capable of aerobic respiration appear.
- 2100 mya: End of Huronian ice age
Orosirian Period (2050 to 1800 mya)
- Intensive orogeny (mountain development)
- 2023 mya: Meteor impact, 300 km crater Vredefort, South Africa
- 2000 mya: Solar luminosity is 85% of current level. - Oxygen starts accumulating in the atmosphere
- 1850 mya: Meteor impact, 250 km crater Sudbury, Ontario, Canada
Statherian Period (1800 to 1600 mya)
- Complex single-celled life appeared.
- Abundant bacteria and archaeans.
Mesoproterozoic Era (1600 to 1000 mya)
Calymmian Period (1600 to 1400 mya)
- Photosynthetic organisms proliferate.
- Oxygen builds up in the atmosphere above 10%.
- Formation of ozone layer starts blocking ultraviolet radiation from the sun.
- 1500 mya: Eukaryotic (nucleated) cells appear.
Ectasian Period (1400 to 1200 mya)
- Green (Chlorobionta) and red (Rhodophyta) algae abound.
Stenian Period (1200 to 1000 mya)
- 1200 mya: Spore/gamete formation indicates origin of sexual reproduction.
- 1100 mya: Formation of the supercontinent Rodinia
Neoproterozoic Era (1000 to 542 mya)
Tonian Period (1000 to 850 mya)
- 1000 mya: Multicellular organisms appear.
- 950 mya: Start of Stuartian-Varangian ice age
- 900 mya: Earth day is 18 hours long. Cryogenian Period (850 to 630 mya)
- 750 mya: Breakup of Rodinia and formation of the supercontinent Pannotia
- 750 mya: End of last magnetic reversal
- 650 mya: Mass extinction of 70% of dominant sea plants due to global glaciation ("Snowball Earth" hypothesis).
Ediacaran (Vendian) Period (630 to 542 mya)
- 570 mya: End of Stuartian-Varangian ice age
- Soft-bodied organisms developed First jellyfish.
- 550 mya: Pannotia fragmented into Laurasia and Gondwana
Phanerozoic Eon(542 mya to present)
Paleozoic Era (542 to 251 mya)
Cambrian Period (542 to 488.3 mya)
- Abundance of multicellular life.
- Most of the major groups of animals first appear
Tommotian Stage (534 to 530 mya)
- Animals with shells appeared Solar brightness was 6% less than today.
Ordovician Period (488.3 to 443.7 mya)
- diverse marine invertebrates, such as trilobites, became common
- First vertebrates appear in the ocean.
- First green plants and fungi on land.
- Fall in atmospheric carbon dioxide.
- 450 mya: Start of Andean-Saharan ice age.
- 443 mya: Glaciation of Gondwana. * Mass extinction of many marine invertebrates. Second largest mass extinction event. 49% of genera of fauna disappeared.
Silurian Period (443.7 to 416 mya)
- 420 mya: End of Andean-Saharan ice age.
- Stabilization of the earth's climate
- Coral reefs appeared
- First fish with jaws - sharks
- Insects (spiders, centipedes), and plants appear on land
Devonian Period (416 to 359.2 mya)
- Ferns and seed-bearing plants (gymnosperms) appeared
- First amphibians appear - Formation of the first forests
- Earth day is ~21.8 hours long. - Wingless insects, and vertebrates appeared on land
- Atmospheric oxygen level is about 16% - 374 mya: * Mass extinction of 70% of marine species. This was a prolonged series of extinctions occurring over 20 million years. Evidence of anoxia in oceanic bottom waters, and global cooling. Surface temperatures dropped from about 93°F (34°C) to about 78°F (26°C)
Carboniferous Period (359.2 to 299 mya)
Mississippian Epoch (359.2 to 318.1 mya)
- 350 mya: Beginning of Karoo ice age.
- Large primitive trees develop
- Oxygen levels increase
- Vertebrates appear on land
- First winged insects.
- Seas covered parts of the continents
- Animals laying amniote eggs appear (318 mya)
Pennsylvanian Epoch (318.1 to 299 mya)
- First reptiles
- Atmospheric oxygen levels reach over 30%
- Earth day is ~22.4 hours long.
- Giant arthropods populate the land
- Transgression and regression of the seas caused by glaciation
- Deposits of coal form in Europe, Asia, and North America
Permian Period (299 to 251 mya)
- 275 mya: Formation of the supercontinent Pangea
- Conifers first appear - Earth is cold and dry
- Sail-backed synapsids like Edaphosaurus and Dimetrodon appeared
- 260 mya: End of Karoo ice age.
- 251 mya: * Mass extinction (Permian-Triassic)
- Possible 480km-wide meteor crater in the Wilkes Land region of Antarctica
- Period of great volcanism in Siberia releases large volume of gases (CO2, CH4, and H2S)
- Oxygen (O2) levels dropped from 30% to 12% Carbon dioxide (CO2) level was about 2000 ppm Earth's worst mass extinction eliminated 90% of ocean dwellers, and 70% of land plants and animals.
Mesozoic Era (251 to 65.5 mya)
Triassic Period (251 to 199.6 mya)
- Break-up of Pangaea starts
- Survivors of P-T extinction spread and recolonize
- Reptiles populate the land. - Sea urchins (Arkarua) appear (240 mya)
- 235 mya: Evolutionary split between dinosaurs and lizards
- Giant marine ichthyosaurs and plesiosaurs populate the seas
- First small dinosaurs such as celophysis appear on land
- Adelobasileus proto-mammal emerged (225 mya)
- 214 mya: Meteor impact, 100 km crater Manicouagan, Quebec, Canada
- First evidence of mammals: Morganucodon (205 mya) - 201 mya: * Mass extinction caused by oceanic anoxic event killed 20% of all marine families
Jurassic Period (199.6 to 145.5 mya)
- Earth is warm. There is no polar ice
- Age of the dinosaurs
- Giant herbivores and vicious carnivores dominate the land
- Flying reptiles (Pterosaurs) appeared.
- North America separates from Africa (180 mya)
- 167 mya: Meteor impact, 80 km crater Puchezh-Katunki, Russia
- 166 mya: Evolutionary split of monotremes from primitive mammals
- 150 mya: First birds like Archaeopteryx appear
-148 mya: Evolutionary split between marsupial and eutherian mammals
- 145 mya: Meteor impact, 70 km crater Morokweng, South Africa
Cretaceous Period (145.5 to 65.5 mya)
- Period of Active Crust Plate Movements
- Africa and India separate from Antarctica (125 mya)
- Global warming event starts (120 mya)
- Flowering plants (angiosperms) appeared
- Crocodiles appeared (110 mya)
- South America breaks away from Africa (105 mya)
- Formation of the Atlantic Ocean - Earth has no polar ice
- Modern mammals and birds developed
- 100 mya: Earth's magnetic field is 3 times stronger than today.
- Global warming event ends (90 mya)
- 70 mya: Tyrannosaurus rex thrived
- 65 mya: Deccan Traps volcanic eruptions in India produce great volume of lava and gases. - 65 mya: Meteor impact, 170 km crater Chicxulub, Yucatan, Mexico
- * Mass extinction of 80-90% of marine species and 85% of land species, including the dinosaurs.
Cenozoic Era (65.5 mya to today)
Paleogene Period (65.5 to 23.03 mya)
Tertiary Period (65.5 to 1.8 mya)
Paleocene Epoch (65.5 to 54.8 mya)
- Appearance of placental mammals (marsupials, insectivores, lemuroids, creodonts)
- 60 mya: Earliest known ungulate (hoofed mammal)
- Formation of the Rocky Mountains
- 55 mya: Major global warming episode North Pole temperature averaged 23°C (73.4°F), CO2 concentration was 2000 ppm. Eocene Epoch (54.8 to 33.7 mya)
- India meets Asia forming the Himalayas (50 mya)
- Australia separates from Antarctica (45 mya) -
Modern mammals appear rhinoceros, camels, early horses appear
- 35.6 mya: Meteor impacts, 90 and 100 km craters Chesapeake Bay, Virginia, USA, and Popigai, Russia
- Global cooling creates permanent Antarctic ice sheet
Oligocene Epoch (33.7 to 23.03 mya)
- Appearance of many grasses
- First elephants with trunks
- 27.8 mya: La Garita, Colorado supervolcanic eruption
Neogene Period (23.03 mya to today)
Miocene Epoch (23.03 to 5.3 mya)
- African-Arabian plate joined to Asia
- Warmer global climates
- First raccoons appear.
- Drying of continental interiors
- Forests give way to grasslands
- 6 mya: Upright walking (bipedal) hominins appear Pliocene Epoch (5.3 to 2.58 mya)
- 4 mya: North and South America join at the Isthmus of Panama. Animals and plants cross the new land bridge. Ocean currents change in the newly isolated Atlantic Ocean.
- 3.7 mya: Australopithecus hominids inhabit Eastern and Northern Africa.
- 3 mya: Formation of Arctic ice cap.
- Accumulation of ice at the poles
- Climate became cooler and drier.
- Spread of grasslands and savannas
- Rise of long-legged grazing animals
Quaternary Period (2.58 mya to today)
Pleistocene Epoch (2.58 mya to 11,400 yrs ago)
- Several major episodes of global cooling, or glaciations
- Homo habilis appeared 2.4 mya
- 2.1 mya: Yellowstone supervolcanic eruption
- 2 mya: Tool-making humanoids emerge.
- Homo erectus first moves out of Africa (1.7 mya)
- 1.3 mya: Yellowstone supervolcanic eruption
- 1.3 mya to 820,000 yrs ago: Sherwin Glaciation
- Presence of large land mammals and birds
- 700,000 yrs ago: Human and Neanderthal lineages start to diverge genetically.
- 680,000 to 620,000 yrs ago: Günz/Nebraskan glacial period
- Yellowstone supervolcanic eruption 640,000 yrs ago
- 530,000 yrs ago: Development of speech in Homo Heidelbergensis
- 455,000 to 300,000 yrs ago: Mindel/Kansan glacial period
- 400,000 yrs ago: Hominids hunt with wooden spears and use stone cutting tools.
- 370,000 yrs ago: Human ancestors and Neanderthals are fully separate populations.
- Hominids use controlled fires (300,000 yrs ago)
- Neanderthal man spreads through Europe 230,000 yrs ago
- 200,000 to 130,000 yrs ago: Riss/Illinoian glacial period
- 160,000 yrs ago: Homo sapiens appeared.
- 110,000 yrs ago: Start of Würm/Wisconsin glacial period
- 74,000 yrs ago: Toba volcanic eruption releases large volume of sulfur dioxide
- Homo sapiens reduced to about 10,000 individuals.
- 70,000 yrs ago: Tahoe glacial maximum glaciers cover Canada and northern US.
- 60,000 yrs ago: Oldest male ancestor of modern humans
- 46,000 yrs ago: Australia becomes arid, bush fires destroy habitat, and megafauna die off. - 40,000 yrs ago: Cro-Magnon man appeared in Europe.
- 26,500 yrs ago: Taupo supervolcanic eruption in New Zealand
- 22,000 yrs ago: Tioga glacial maximum sea level was 130 meters lower than today
- 19,000 yrs ago: Antarctic sea ice starts melting
- 15,000 yrs ago: Bering land bridge between Alaska and Siberia allows human migration to America
- 12,900 yrs ago: Explosion of comet over Canada, causes extinction of American megafauna such as the mammoth and sabretooth cat (Smilodon), as well as the end of Clovis culture - Fired pottery invented (12,000 yrs ago)
- 11,400 yrs ago: End of Würm/Wisconsin glacial period. Sea level rises by 91 meters (300 ft)
Holocene Epoch (11,400 years ago to today)
- Development of agriculture - Domestication of animals.
- Metal smelting started (9,000 yrs ago)
- Invention of the wheel (5,500 yrs ago)
- Development of writing (5,000 yrs ago)
- Pyramids of Giza (4,500 yrs ago)
- Archimedes advances mathematics (2,230 yrs ago)
- Start of the Industrial Revolution (250 yrs ago)
- Space travel (50 yrs ago)
Artificial satellite orbits the earth (1957).
Humans walk on the surface of the moon (1969).
