The
geologic time scale provides a system of
chronologic measurement relating
stratigraphy to time that is used by
geologists,
paleontologists and other
earth scientists to describe the timing and
relationships between events that have occurred during the
history of the Earth. The table of geologic time
spans presented here agrees with the dates and
nomenclature proposed by the
International Commission on Stratigraphy, and uses
the standard color codes of the
United States Geological Survey.
Evidence from
radiometric dating indicates that the
Earth
is about 4.570 billion years old. The geological or
deep
time of Earth's past has been organized into various units
according to events which took place in each period. Different spans of time on
the time scale are usually delimited by major geological or
paleontological events, such as
mass
extinctions. For example, the boundary between the
Cretaceous period and the
Paleogene period is defined by the
Cretaceous–Tertiary extinction event, which marked
the demise of the
dinosaurs and of many marine species. Older periods
which predate the reliable fossil record are defined by absolute age.
Each era on the scale is separated from the next by a major event or
change.
Geologic time scale
Supereon Eon Era Period[17] Epoch Age[18] Major events
Start, million years ago
[18] Phanerozoic Cenozoic[19] Quaternary Holocene Nonechrons:
SubatlanticSubborealAtlanticBorealPreboreal
The
last
glacial period ends; rise of human
civilization.
Quaternary
Ice Age recedes, and the current
interglacial begins.
Younger
Dryas cold spell occurs,
Sahara forms from savannah, and
agriculture begins, allowing humans to build
cities.
Paleolithic/
Neolithic (
Stone Age) cultures begin
around
10000
BC, giving way to
Copper
Age (3500 BC) and
Bronze
Age (2500 BC). Cultures continue to grow in complexity and technical
advancement through the
Iron
Age (1200 BC), giving rise to
many
pre-historic cultures throughout the world, eventually leading into
Classical
Antiquity, such as the
Roman
Empire and even to the
Middle
Ages and
present
day.
Little
Ice Age (
stadial) causes brief cooling in
Northern
Hemisphere from 1400 to 1850. Also refer to the
List of
archaeological periods for clarification on early cultures and ages.
Mount
Tambora erupts in 1815, causing the
Year
Without a Summer (1816) in Europe and North America from a
volcanic winter.
Following the
Industrial
Revolution,
Atmospheric CO2 levels
rise from around 280
parts
per million volume (ppmv) to the current level of 390 ppmv, due to
anthropogenic emissions,
very
likely causing
global
warming and
climate
change.
[20] 0.011430 ± 0.00013
[19][21] Pleistocene Tarantian(
Tyrrhenian
Stage/
Eemian/
Sangamonian)
Flourishing and then extinction of many large
mammals (
Pleistocene
megafauna). Evolution of anatomically modern
humans.
Quaternary
Ice Age continues with
glaciations and
interstadials (and the accompanying fluctuations from 100 to 300 ppmv in
atmospheric CO2 levels
[20]),
further intensification of
Icehouse
Earth conditions, roughly 1.6
Ma.
Last
glacial maximum (30000
years
ago),
last
glacial period (18000–15000 years ago). Dawn of human
stone-age
cultures, with
increasing
technical complexity relative to previous ice age cultures, such as
engravings
and clay statues (e.g.
Venus
of Lespugue), particularly in the
Mediterranean and Europe.
Lake Toba supervolcano erupts 75000
years before present, causing a
volcanic
winter that
pushes
humanity to the brink of extinction. Pleistocene ends with
Oldest Dryas,
Older Dryas/
Allerød and
Younger Dryas climate
events, with Younger Dryas forming the boundary with the Holocene.
0.126 ± 0.005*
Ionian 0.781 ± 0.005*
Calabrian 1.806 ± 0.005*
Gelasian 2.588 ± 0.005*
Neogene Pliocene Piacenzian/
Blancan Intensification of present
Icehouse
conditions,
present
(Quaternary) ice age begins roughly 2.58 Ma; cool and dry
climate.
Australopithecines,
many of the existing genera of mammals, and recent
mollusks appear.
Homo habilis appears.
3.600 ± 0.005*
Zanclean 5.332 ± 0.005*
Miocene Messinian Moderate
Icehouse climate, puncuated by
ice
ages;
Orogeny in
northern
hemisphere. Modern
mammal and
bird families
become recognizable.
Horses and
mastodons diverse.
Grasses become ubiquitous. First
apes appear (for
reference see the article: "
Sahelanthropus
tchadensis").
Kaikoura
Orogeny forms
Southern
Alps in New Zealand, continues today. Orogeny of the Alps in Europe slows,
but continues to this day.
Carpathian
orogeny forms
Carpathian
Mountains in
Central and
Eastern Europe.
Hellenic
orogeny in Greece and Aegean Sea slows, but continues to this day.
Middle
Miocene Disruption occurs. Widespread forests slowly
draw in massive amounts
of CO2, gradually lowering the level of atmospheric CO2
from 650 ppmv down to around 100 ppmv
[20].
7.246 ± 0.05*
Tortonian 11.608 ± 0.05*
Serravallian 13.65 ± 0.05*
Langhian 15.97 ± 0.05*
Burdigalian 20.43 ± 0.05*
Aquitanian 23.03 ± 0.05*
Paleogene Oligocene Chattian Warm but
cooling climate, moving towards Icehouse; Rapid
evolution and diversification of fauna, especially
mammals.
Major evolution and dispersal of modern types of
flowering plants 28.4 ± 0.1*
Rupelian 33.9 ± 0.1*
Eocene Priabonian Moderate,
cooling climate. Archaic
mammals (e.g.
Creodonts,
Condylarths,
Uintatheres, etc)
flourish and continue to develop during the epoch. Appearance of several
"modern" mammal families. Primitive
whales diversify. First
grasses. Reglaciation of
Antarctica and formation of its
ice
cap;
Azolla
event triggers
ice
age, and the
Icehouse
Earth climate that would follow it to this day, from the settlement and
decay of
seafloor algae drawing in
massive amounts of atmospheric
carbon
dioxide[20],
lowering it from 3800
ppmv down to 650 ppmv. End of
Laramide and
Sevier Orogenies of the
Rocky Mountains in North
America.
Orogeny of the
Alps in Europe begins.
Hellenic
Orogeny begins in Greece and
Aegean
Sea.
37.2 ± 0.1*
Bartonian 40.4 ± 0.2*
Lutetian 48.6 ± 0.2*
Ypresian 55.8 ± 0.2*
Paleocene Thanetian Climate
tropical. Modern
plants appear;
Mammals diversify into a number
of primitive lineages following the extinction of the dinosaurs. First large
mammals (up to
bear or small
hippo size).
Alpine
orogeny in Europe and Asia begins.
Indian Subcontinent collides with Asia 55
Ma,
Himalayan
Orogeny starts between 52 and 48
Ma.
58.7 ± 0.2*
Selandian 61.7 ± 0.3*
Danian 65.5 ± 0.3*
Mesozoic Cretaceous Late Maastrichtian Flowering
plants proliferate, along with new types of
insects.
More modern
teleost fish begin to appear.
Ammonites,
belemnites,
rudist bivalves,
echinoids and
sponges all common. Many new types of
dinosaurs (e.g.
Tyrannosaurs,
Titanosaurs,
duck
bills, and
horned
dinosaurs) evolve on land, as do
Eusuchia (
modern
crocodilians); and
mosasaurs and modern
sharks appear in the sea. Primitive
birds gradually replace
pterosaurs.
Monotremes,
marsupials and
placental mammals appear. Break
up of
Gondwana. Beginning of
Laramide and
Sevier
Orogenies of the
Rocky
Mountains.
Atmospheric CO2 close to present-day levels.
70.6 ± 0.6*
Campanian 83.5 ± 0.7*
Santonian 85.8 ± 0.7*
Coniacian 89.3 ± 1.0*
Turonian 93.5 ± 0.8*
Cenomanian 99.6 ± 0.9*
Early Albian 112.0 ± 1.0*
Aptian 125.0 ± 1.0*
Barremian 130.0 ± 1.5*
Hauterivian 136.4 ± 2.0*
Valanginian 140.2 ± 3.0*
Berriasian 145.5 ± 4.0*
Jurassic Late Tithonian Gymnosperms (especially
conifers,
Bennettitales and
cycads) and
ferns common. Many
types of
dinosaurs, such as
sauropods,
carnosaurs,
and
stegosaurs.
Mammals common but small. First
birds and
lizards.
Ichthyosaurs and
plesiosaurs diverse.
Bivalves,
Ammonites and
belemnites abundant.
Sea
urchins very common, along with
crinoids,
starfish,
sponges,
and
terebratulid and
rhynchonellid brachiopods. Breakup of
Pangaea into
Gondwana and
Laurasia.
Nevadan orogeny in North
America.
Rantigata and
Cimmerian
Orogenies taper off. Atmospheric CO2 levels 4–5 times the present
day levels (1200–1500 ppmv, compared to today's 385 ppmv
[20]).
150.8 ± 4.0*
Kimmeridgian 155.7 ± 4.0*
Oxfordian 161.2 ± 4.0*
Middle Callovian 164.7 ± 4.0
Bathonian 167.7 ± 3.5*
Bajocian 171.6 ± 3.0*
Aalenian 175.6 ± 2.0*
Early Toarcian 183.0 ± 1.5*
Pliensbachian 189.6 ± 1.5*
Sinemurian 196.5 ± 1.0*
Hettangian 199.6 ± 0.6*
Triassic Late Rhaetian Archosaurs dominant on land as
dinosaurs,
in the oceans as
Ichthyosaurs and
nothosaurs, and in the air as
pterosaurs.
Cynodonts become smaller and
more mammal-like, while first
mammals and
crocodilia appear.
Dicroidium flora common
on land. Many large aquatic
temnospondyl amphibians.
Ceratitic ammonoids extremely
common.
Modern corals and
teleost fish
appear, as do many modern
insect clades.
Andean
Orogeny in South America.
Cimmerian
Orogeny in Asia.
Rangitata
Orogeny begins in New Zealand.
Hunter-Bowen
Orogeny in
Northern
Australia, Queensland and
New
South Wales ends, (c. 260–225
Ma)
203.6 ± 1.5*
Norian 216.5 ± 2.0*
Carnian 228.0 ± 2.0*
Middle Ladinian 237.0 ± 2.0*
Anisian 245.0 ± 1.5*
Early Olenekian 249.7 ± 1.5*
Induan 251.0 ± 0.7*
Paleozoic Permian Lopingian Changhsingian Landmasses unite into
supercontinent Pangaea, creating the
Appalachians. End of
Permo-Carboniferous glaciation.
Synapsid reptiles (
pelycosaurs and
therapsids)
become plentiful, while
parareptiles and
temnospondyl amphibians remain common. In the mid-Permian,
coal-age
flora are replaced by
cone-bearing
gymnosperms (the first true
seed
plants) and by the first true
mosses.
Beetles and
flies evolve.
Marine life flourishes in warm shallow reefs;
productid and
spiriferid brachiopods,
bivalves,
forams,
and
ammonoids all abundant.
Permian-Triassic
extinction event occurs 251
Ma:
95% of life on Earth becomes extinct, including all
trilobites,
graptolites,
and
blastoids.
Ouachita and
Innuitian orogenies in
North America.
Uralian
orogeny in Europe/Asia tapers off.
Altaid orogeny in Asia.
Hunter-Bowen
Orogeny on
Australian
Continent begins (c. 260–225
Ma),
forming the
MacDonnell
Ranges.
253.8 ± 0.7*
Wuchiapingian 260.4 ± 0.7*
Guadalupian Capitanian 265.8 ± 0.7*
Wordian/Kazanian 268.4 ± 0.7*
Roadian/Ufimian 270.6 ± 0.7*
Cisuralian Kungurian 275.6 ± 0.7*
Artinskian 284.4 ± 0.7*
Sakmarian 294.6 ± 0.8*
Asselian 299.0 ± 0.8*
Carbon-
iferous[22]/Pennsyl-
vanian Late Gzhelian Winged
insects radiate suddenly; some (esp.
Protodonata and
Palaeodictyoptera)
are quite large.
Amphibians common and diverse. First
reptiles and
coal forests
(
scale trees, ferns,
club
trees,
giant horsetails,
Cordaites, etc.).
Highest-ever
atmospheric oxygen levels.
Goniatites, brachiopods,
bryozoa, bivalves, and corals plentiful in the seas and oceans. Testate
forams proliferate.
Uralian orogeny in
Europe and Asia.
Variscan
orogeny occurs towards middle and late Mississippian Periods.
303.9 ± 0.9*
Kasimovian 306.5 ± 1.0*
Middle Moscovian 311.7 ± 1.1*
Early Bashkirian 318.1 ± 1.3*
Carbon-
iferous[22]/Missis-
sippian Late Serpukhovian Large
primitive
trees, first
land
vertebrates, and amphibious
sea-scorpions live amid
coal-forming coastal
swamps. Lobe-finned
rhizodonts are dominant big fresh-water predators. In the oceans, early
sharks are common and
quite diverse;
echinoderms (especially
crinoids and
blastoids) abundant.
Corals,
bryozoa,
goniatites and brachiopods (
Productida,
Spiriferida, etc.) very
common, but
trilobites and
nautiloids decline.
Glaciation in East
Gondwana.
Tuhua
Orogeny in New Zealand tapers off.
326.4 ± 1.6*
Middle Viséan 345.3 ± 2.1*
Early Tournaisian 359.2 ± 2.5*
Devonian Late Famennian First
clubmosses,
horsetails and
ferns appear,
as do the first
seed-bearing plants (
progymnosperms), first
trees (the
progymnosperm
Archaeopteris),
and first (wingless)
insects.
Strophomenid and
atrypid brachiopods,
rugose and
tabulate corals, and
crinoids are all abundant in the
oceans.
Goniatite ammonoids are plentiful, while
squid-like
coleoids arise. Trilobites and
armoured agnaths decline, while jawed fishes (
placoderms,
lobe-finned and
ray-finned fish, and early
sharks) rule the seas.
First
amphibians still aquatic. "Old
Red Continent" of
Euramerica.
Beginning of
Acadian
Orogeny for
Anti-Atlas
Mountains of
North
Africa, and
Appalachian
Mountains of North America, also the
Antler,
Variscan, and
Tuhua
Orogeny in New Zealand.
374.5 ± 2.6*
Frasnian 385.3 ± 2.6*
Middle Givetian 391.8 ± 2.7*
Eifelian 397.5 ± 2.7*
Early Emsian 407.0 ± 2.8*
Pragian 411.2 ± 2.8*
Lochkovian 416.0 ± 2.8*
Silurian Pridoli no faunal stages defined First
Vascular
plants (the
rhyniophytes and their relatives), first
millipedes and
arthropleurids on land. First
jawed
fishes, as well as many
armoured jawless fish,
populate the seas.
Sea-scorpions reach large size.
Tabulate and
rugose corals,
brachiopods (
Pentamerida,
Rhynchonellida,
etc.), and
crinoids all abundant.
Trilobites and
mollusks diverse;
graptolites not as varied. Beginning of
Caledonian Orogeny for hills in England, Ireland, Wales, Scotland, and the
Scandinavian
Mountains. Also continued into Devonian period as the
Acadian Orogeny, above.
Taconic
Orogeny tapers off.
Lachlan
Orogeny on
Australian
Continent tapers off.
418.7 ± 2.7*
Ludlow/
Cayugan Ludfordian 421.3 ± 2.6*
Gorstian 422.9 ± 2.5*
Wenlock Homerian/
Lockportian 426.2 ± 2.4*
Sheinwoodian/
Tonawandan 428.2 ± 2.3*
Llandovery/
Alexandrian Telychian/
Ontarian 436.0 ± 1.9*
Aeronian 439.0 ± 1.8*
Rhuddanian 443.7 ± 1.5*
Ordovician Late Hirnantian Invertebrates diversify into many new types (e.g., long
straight-shelled cephalopods). Early
corals, articulate
brachiopods (
Orthida,
Strophomenida, etc.),
bivalves,
nautiloids,
trilobites,
ostracods,
bryozoa, many types of
echinoderms (
crinoids,
cystoids,
starfish,
etc.), branched
graptolites,
and other taxa all common.
Conodonts (early
planktonic vertebrates) appear. First
green
plants and
fungi on land. Ice age at end of
period.
445.6 ± 1.5*
other
faunal stages 460.9 ± 1.6*
Middle Darriwilian 468.1 ± 1.6*
other
faunal stages 471.8 ± 1.6*
Early Arenig 478.6 ± 1.7*
Tremadocian 488.3 ± 1.7*
Cambrian Furongian other
faunal stages Major diversification of life in the
Cambrian
Explosion. Numerous fossils; most modern
animal phyla appear. First
chordates appear, along with a number of extinct, problematic phyla. Reef-building
Archaeocyatha abundant;
then vanish.
Trilobites,
priapulid worms,
sponges,
inarticulate
brachiopods (unhinged lampshells), and many other animals numerous.
Anomalocarids are giant
predators, while many Ediacaran fauna die out.
Prokaryotes,
protists (e.g.,
forams),
fungi and
algae continue to
present day.
Gondwana emerges.
Petermann Orogeny on
the
Australian
Continent tapers off (550–535
Ma).
Ross Orogeny in Antarctica.
Adelaide
Geosyncline (Delamerian Orogeny), majority of orogenic activity from 514–500
Ma.
Lachlan Orogeny on
Australian
Continent, c. 540–440
Ma.
Atmospheric CO2 content roughly 20–35 times present-day (
Holocene) levels (6000 ppmv
compared to today's 385 ppmv)
[20] 496.0 ± 2.0*
Paibian/
Ibexian/
Ayusokkanian/
Sakian/
Aksayan 501.0 ± 2.0*
Middle other
faunal stages/
Albertan 513.0 ± 2.0
Early other
faunal stages/
Waucoban/
Tommotian/
Atdabanian/
Botomian 542.0 ± 1.0*
Precam-
brian[23] Proter-
ozoic[24] Neo-
proterozoic[24] Ediacaran Good
fossils of the first
multi-celled
animals.
Ediacaran
biota flourish worldwide in seas. Simple
trace
fossils of possible worm-like
Trichophycus,
etc. First
sponges and
trilobitomorphs.
Enigmatic forms include many soft-jellied creatures shaped like bags, disks, or
quilts (like
Dickinsonia).
Taconic
Orogeny in North America.
Aravalli
Range orogeny in
Indian
Subcontinent. Beginning of
Petermann
Orogeny on
Australian
Continent. Beardmore Orogeny in Antarctica, 633–620
Ma.
630 +5/-30*
Cryogenian Possible "
Snowball
Earth" period.
Fossils still rare.
Rodinia landmass begins to break
up. Late Ruker / Nimrod Orogeny in Antarctica tapers off.
850
[25] Tonian Rodinia supercontinent persists.
Trace
fossils of simple
multi-celled eukaryotes.
First radiation of
dinoflagellate-like
acritarchs.
Grenville Orogeny tapers off in North America.
Pan-African
orogeny in Africa. Lake Ruker / Nimrod Orogeny in Antarctica, 1000 ± 150
Ma. Edmundian
Orogeny (c. 920 - 850
Ma),
Gascoyne Complex,
Western Australia.
Adelaide
Geosyncline laid down on
Australian
Continent, beginning of
Adelaide
Geosyncline (Delamerian Orogeny) in that continent.
1000
[25] Meso-
proterozoic[24] Stenian Narrow highly
metamorphic belts due to
orogeny as
Rodinia forms. Late Ruker /
Nimrod Orogeny in Antarctica possibly begins. Musgrave Orogeny (c. 1080
Ma),
Musgrave Block,
Central
Australia.
1200
[25] Ectasian Platform
covers continue to expand.
Green
algae colonies in the seas.
Grenville
Orogeny in North America.
1400
[25] Calymmian Platform
covers expand. Barramundi Orogeny,
McArthur
Basin,
Northern
Australia, and Isan Orogeny,
c. 1600
Ma,
Mount Isa Block, Queensland
1600
[25] Paleo-
proterozoic[24] Statherian First
complex
single-celled life:
protists with nuclei.
Columbia is the primordial supercontinent. Kimban Orogeny in Australian Continent ends.
Yapungku Orogeny on
Yilgarn
craton, in Western Australia. Mangaroon Orogeny, 1680–1620
Ma, on the
Gascoyne Complex in
Western Australia. Kararan Orogeny (1650-
Ma),
Gawler Craton,
South
Australia.
1800
[25] Orosirian The
atmosphere become
oxygenic.
Vredefort and
Sudbury Basin asteroid
impacts. Much
orogeny.
Penokean and
Trans-Hudsonian
Orogenies in North America. Early Ruker Orogeny in Antarctica, 2000 - 1700
Ma. Glenburgh
Orogeny,
Glenburgh
Terrane,
Australian
Continent c. 2005–1920
Ma.
Kimban Orogeny,
Gawler
craton in Australian Continent begins.
2050
[25] Rhyacian Bushveld
Igneous Complex forms.
Huronian glaciation.
2300
[25] Siderian Oxygen
catastrophe:
banded
iron formations forms. Sleaford Orogeny on
Australian
Continent,
Gawler
Craton 2440–2420
Ma.
2500
[25] Archean[24] Neoarchean[24] Stabilization of most modern
cratons;
possible
mantle overturn event. Insell Orogeny, 2650 ± 150
Ma.
Abitibi
greenstone belt in present-day
Ontario and
Quebec begins to form, stablizes by 2600
Ma.
2800
[25] Mesoarchean[24] First
stromatolites (probably
colonial cyanobacteria). Oldest
macrofossils. Humboldt
Orogeny in Antarctica.
Blake
River Megacaldera Complex begins to form in present-day
Ontario and
Quebec, ends by roughly 2696
Ma.
3200
[25] Paleoarchean[24] First known
oxygen-producing bacteria.
Oldest definitive
microfossils.
Oldest
cratons on Earth (such as the
Canadian
Shield and the
Pilbara
Craton) may have formed during this period
[26].
Rayner Orogeny in Antarctica.
3600
[25] Eoarchean[24] Simple
single-celled life (probably
bacteria and
archaea).
Oldest probable
microfossils.
3800
Hadean[24][27] Early
Imbrian[24][28] Indirect
photosynthetic evidence (e.g.,
kerogen) of primordial life.
This era overlaps the end of the
Late
Heavy Bombardment of the
inner solar
system.
c.3850
Nectarian[24][28] This unit gets its name from the
lunar geologic
timescale when the
Nectaris
Basin and other greater
lunar
basins form by big
impact
events.
c.3920
Basin
Groups[24][28] Oldest known rock (4030
Ma)
[29].
The first
life
forms and
self-replicating RNA molecules evolve around 4000
Ma after the
Late
Heavy Bombardment ends on Earth.
Napier Orogeny in Antarctica, 4000 ± 200
Ma.
c.4150
Cryptic[24][28] Oldest known
mineral (
Zircon, 4406 ±
8
Ma).
[30] Formation of
Moon (4533
Ma),
probably from
giant
impact. Formation of
Earth (4567.17 to 4570
Ma)
c.4570