Geologic Time Scale

Geologic Time Scale

EON ERA PERIOD EPOCH MILLIONS
OF YRS
AGO MAJOR BIOLOGICAL EVENTS

P
H
A
N
E
R
O
Z
O
I
C C
E
N
O
Z
O
I
C Quaternary Holocene
.01
Rise of civilization and agriculture. Extinction of large mammals in northern hemisphere.

Pleistocene 1.8 Modern humans appear. Four major glaciations cause rapid shifts in ecological communities.

Tertiary Neogene Pliocene 5 Extensive radiation of flowering plants and mammals. First hominids appear.

Miocene 23 Coevolution of insects and flowering plants. Dogs and bears appear.

Paleogene Oligocene 38 Worldwide tropical rainforests. Pigs, cats, and rhinos appear. Dominence of snails and bivalves in the oceans.

Eocene 54 Early mammals abundant. Rodents, primitive whales and grasses appear.

Paleocene 65 Early placental mammals appear; first primates; modern birds.

M
E
S
O
Z
O
I
C Cretaceous 146 Marsupials, ants, bees, butterflies, flowering plants appear. Mass extinction of most large animals and many plants.

Jurassic 208 Dinosaurs and gymnosperms dominate the land; feathered dinosaurs and birds appear. Radiation of marine reptiles.

Triassic 245 Origin of mammals, dinosaurs and true flies. Less diverse marine fauna.

P
A
L
E
O
Z
O
I
C Permian 286
Gymnosperms, amphibians dominant. Beetles, stoneflies appear. Major extinction of 95% of marine species and 50% of all animal families.

Carboniferous Pennsylvanian
325

First reptiles, cockroaches and mayflies appear. Extensive coal swamp forests. Sponge reefs.

Missippian 360 Echinoderms, bryozoans dominant in oceans. Early winged insects. First coal swamp forests.

Devonian 410 First amphibians. Extensive radiation of fish, land plants. Many corals, brachiopods and echinoderms.

Silurian 440
First spiders, scorpions, centipedes, early insects, vascular plants, jawed fish and large reefs appear.

Ordovician 505
First land plants, primitive fungi, sea weed appear. Diverse marine life: corals, molluscs, bivalves, echinoderms, etc.

Cambrian 543 Rise of all major animal groups. Metazoan life abundant; trilobites dominant. First fish. No known terrestrial life.

PROTEROZOIC EON
570 Origin of multicelled organisms. First sponges, colonial algae and soft-bodied invertebrates.

ARCHEAN EON 2,500
Oxygen levels rise as a result of photosynthetic organisms.
First eukaryotes (single-celled algae): 1.4 billion years old.
Earliest life, anaerobic prokaryotes (bacteria, archaeans) originate 3.5 billion years ago.

HADEAN EON 3,800-4,600 No life known. Cooling and solidifying of Earth's crust.

EON	ERA	PERIOD		EPOCH	MILLIONS OF YRS AGO	MAJOR BIOLOGICAL EVENTS
P H A N E R O Z O I C	C E N O Z O I C	Quaternary		Holocene	.01	Rise of civilization and agriculture. Extinction of large mammals in northern hemisphere.
		Quaternary		Pleistocene	1.8	Modern humans appear. Four major glaciations cause rapid shifts in ecological communities.
		Tertiary	Neogene	Pliocene	5	Extensive radiation of flowering plants and mammals. First hominids appear.
			Neogene	Miocene	23	Coevolution of insects and flowering plants. Dogs and bears appear.
			Paleogene	Oligocene	38	Worldwide tropical rainforests. Pigs, cats, and rhinos appear. Dominence of snails and bivalves in the oceans.
				Eocene	54	Early mammals abundant. Rodents, primitive whales and grasses appear.
				Paleocene	65	Early placental mammals appear; first primates; modern birds.
	M E S O Z O I C	Cretaceous			146	Marsupials, ants, bees, butterflies, flowering plants appear. Mass extinction of most large animals and many plants.
		Jurassic			208	Dinosaurs and gymnosperms dominate the land; feathered dinosaurs and birds appear. Radiation of marine reptiles.
		Triassic			245	Origin of mammals, dinosaurs and true flies. Less diverse marine fauna.
	P A L E O Z O I C	Permian			286	Gymnosperms, amphibians dominant. Beetles, stoneflies appear. Major extinction of 95% of marine species and 50% of all animal families.
		Carboniferous		Pennsylvanian	325	First reptiles, cockroaches and mayflies appear. Extensive coal swamp forests. Sponge reefs.
		Carboniferous		Missippian	360	Echinoderms, bryozoans dominant in oceans. Early winged insects. First coal swamp forests.
		Devonian			410	First amphibians. Extensive radiation of fish, land plants. Many corals, brachiopods and echinoderms.
		Silurian			440	First spiders, scorpions, centipedes, early insects, vascular plants, jawed fish and large reefs appear.
		Ordovician			505	First land plants, primitive fungi, sea weed appear. Diverse marine life: corals, molluscs, bivalves, echinoderms, etc.
		Cambrian			543	Rise of all major animal groups. Metazoan life abundant; trilobites dominant. First fish. No known terrestrial life.
PROTEROZOIC EON					570	Origin of multicelled organisms. First sponges, colonial algae and soft-bodied invertebrates.
ARCHEAN EON					2,500	Oxygen levels rise as a result of photosynthetic organisms. First eukaryotes (single-celled algae): 1.4 billion years old. Earliest life, anaerobic prokaryotes (bacteria, archaeans) originate 3.5 billion years ago.
HADEAN EON					3,800-4,600	No life known. Cooling and solidifying of Earth's crust.