Triassic Period
251.902–201.3 million years ago
Mean atmospheric O
content over period duration
c. 16 vol % [1] [2]
(80 % of modern level
Mean atmospheric CO
content over period duration
c. 1750 ppm [3]
(6 times pre-industrial level)
Mean surface temperature over period duration c. 17 °C [4]
(3 °C above modern level)
Key events in the Triassic
view •   • 
-255 —
-250 —
-245 —
-240 —
-235 —
-230 —
-225 —
-220 —
-215 —
-210 —
-205 —
-200 —
Full recovery of woody trees [5]
Coals return [6]
corals & calcified sponges [7]
An approximate timescale of key Triassic events.
Axis scale: millions of years ago.

The Triassic ( k/) is a geologic period and system which spans 50.9 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.3 Mya. [8] The Triassic is the first period of the Mesozoic Era. Both the start and end of the period are marked by major extinction events. [9]

The Triassic began in the wake of the Permian–Triassic extinction event, which left the earth's biosphere impoverished; it would take well into the middle of this period for life to recover its former diversity. Therapsids and archosaurs were the chief terrestrial vertebrates during this time. A specialized subgroup of archosaurs, called dinosaurs, first appeared in the Late Triassic but did not become dominant until the succeeding Jurassic Period. [10]

The first true mammals, themselves a specialized subgroup of Therapsids, also evolved during this period, as well as the first flying vertebrates, the pterosaurs, who like the dinosaurs were a specialized subgroup of archosaurs. The vast supercontinent of Pangaea existed until the mid-Triassic, after which it began to gradually rift into two separate landmasses, Laurasia to the north and Gondwana to the south.

The global climate during the Triassic was mostly hot and dry, [11] with deserts spanning much of Pangaea's interior. However, the climate shifted and became more humid as Pangaea began to drift apart. The end of the period was marked by yet another major mass extinction, the Triassic–Jurassic extinction event, that wiped out many groups and allowed dinosaurs to assume dominance in the Jurassic.

The Triassic was named in 1834 by Friedrich von Alberti, after the three distinct rock layers (tri meaning "three") that are found throughout Germany and northwestern Europered beds, capped by marine limestone, followed by a series of terrestrial mud- and sandstones—called the "Trias". [12]

Dating and subdivisions

The Triassic is usually separated into Early, Middle, and Late Triassic Epochs, and the corresponding rocks are referred to as Lower, Middle, or Upper Triassic. The faunal stages from the youngest to oldest are:

Upper/Late Triassic (Tr3)
  Rhaetian (208.5 – 201.3 Mya)
  Norian (227 – 208.5 Mya)
  Carnian (237– 227 Mya)
Middle Triassic (Tr2)
  Ladinian (242 – 237 Mya)
  Anisian (247.2 – 242 Mya)
Lower/Early Triassic (Scythian)
  Olenekian (251.2 – 247.2 Mya)
  Induan (251.902– 251.2 Mya)
Other Languages
Afrikaans: Trias
Alemannisch: Trias (Geologie)
العربية: عصر ثلاثي
asturianu: Triásicu
azərbaycanca: Trias dövrü
Bân-lâm-gú: Trias-kí
беларуская: Трыясавы перыяд
беларуская (тарашкевіца)‎: Трыяс
български: Триас
bosanski: Trijas
brezhoneg: Triaseg
català: Triàsic
čeština: Trias
Cymraeg: Triasig
dansk: Trias
eesti: Triias
español: Triásico
Esperanto: Triaso
euskara: Triasiko
فارسی: تریاس
français: Trias
Gaeilge: Triasach
galego: Triásico
hrvatski: Trijas
Ido: Triaso
Bahasa Indonesia: Trias
italiano: Triassico
עברית: טריאס
қазақша: Триас дәуірі
Кыргызча: Триас мезгили
Latina: Triassicum
latviešu: Triass
Lëtzebuergesch: Trias
lietuvių: Triasas
magyar: Triász
مازِرونی: تریاس
Bahasa Melayu: Trias
Mìng-dĕ̤ng-ngṳ̄: Triassic
Nederlands: Trias
日本語: 三畳紀
norsk: Trias
norsk nynorsk: Trias
occitan: Triassic
oʻzbekcha/ўзбекча: Trias sistemasi
پنجابی: ٹرائیسک
Piemontèis: Triàssich
Plattdüütsch: Trias (Geologie)
polski: Trias
português: Triássico
română: Triasic
саха тыла: Триас
Scots: Triassic
Simple English: Triassic
slovenčina: Trias
slovenščina: Trias
српски / srpski: Тријас
srpskohrvatski / српскохрватски: Trijas
suomi: Triaskausi
svenska: Trias
Tagalog: Triassic
татарча/tatarça: Триас
Türkçe: Trias Devri
українська: Тріасовий період
Tiếng Việt: Kỷ Trias
粵語: 三疊紀
中文: 三叠纪