|
|
GEOLOGIC TIME SCALE:
FROM 4600 MILLION YEARS AGO TO PRESENT
millions
of years
ago era period notes
4600 ^ Precambrian Precambrian The formation of the
| . . Earth's crust and the
| . . subsequent evolution of
| . . life
|
4550 +
|
\ (Note: Precambrian era lasts from 4600 million years ago to 570
/ million years ago, a span of over four billion years. A time-
\ line showing this would extend another 403 lines, or roughly 7
/ pages.)
|
600 +
|
|
| Palaeozoic Cambrian Marine animals with
| . . mineralized shells
550 + . . appear: trilobites,
| . . echinoderms, brachio-
| pods, molluscs,
| primitive graptolites;
| a variety of worms
500 + Ordovician Graptolites dominant;
| . also trilobites,
| . brachiopods, bryozoans,
| . gastropods, bivalves,
| echinoids, crinoids,
450 + cephalopods, and corals
| Silurian Barchiopods, crinoids,
| . corals, corals; prim-
| . itive fish
| .
400 + Devonian (395) Corals, brachiopods,
| . ammonoids, crinoids;
| . fishes and early land
| . plants
|
350 + Carboniferous (345) Foraminiferans, corals,
| . bryozoans, brachiopods,
| . blastoids; seed ferns,
| . lycopsids, and other
| plants; amphibians
300 + become more common
|
| Permian Trilobites extinct;
| . Amphibians and reptiles
| . dominant land animals;
250 + . gymnosperms dominant
| plants
| Mesozoic Triassic Molluscs dominant
| . . invertebrates; reptiles
| . . dominant: turtles,
200 + . . dinosaurs, ichthyosaurs
| Jurassic Ferns, cycads, ginkgos,
| . rushes, conifers; ammo-
| . nites and other inver-
| . tebrates; pterosaurs,
150 + _Archaeopteryx_ appears
| Cretaceous (136) Angiosperm plants;
| . Mesozoic reptiles peak
| .
| .
100 +
|
|
| Cenozoic Tertiary (65) Mass extinction: dino-
| . . saurs, pterosaurs, and
50 + . . ammonites extinct; rise
| . . of modern animals;
| shrubs, grasses, and
| other flowering plants
| .
PRESENT + Quarternary (1.8) .
v
INSET: CENOZOIC ERA
millions
of years
ago era period epoch notes
^
|
65 + Cenozoic Tertiary Palaeocene Mammals become abundant
| . . . after extinction of
| . . . dinosaurs and large
| . . . reptiles; by the
| beginning of the Eocene
60 + rodents and primates
| have evolved
|
|
|
55 +
| Eocene Mammals dominant:
| . rodents, artiodactyls,
| . carnivores, perisso-
| . dactyls (including
50 + horses); whales make
| their first appearance
|
|
|
45 +
|
|
|
|
40 +
|
| Oligocene Continued rise of
| . mammals: pigs,
| . rhinoceroses, and
35 + . tapirs make their
| appearance
|
|
|
30 +
|
|
|
| Miocene More and more modern
25 + . mammals: horses, dogs
| . and bears, modern
| . whales, South American
| monkeys; modern birds,
| apes present in
20 + southern Europe,
| _Ramapithecus_ appears
|
|
|
15 +
|
|
|
|
10 +
|
|
| Pliocene Mammals similar to
| . modern forms evolve;
5 + . australopithecines
| . appear, the forerunners
| of humanity, appear
| Quarternary Pleistocene (1.8) Ice ages; _Homo
| . . sapiens_ evolves
PRESENT + . Holocene (0.01) Human history
v