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| GEOLOGIC TIMELINE |
| Cenozoic Era (Recent Life). Two periods: Quaternary and Tertiary |
| Quaternary Period: Holocene and Pleistocene Epochs |
| Time | Geologic Development | Life Forms |
| Holocene Epoch
10,000 years ago to the present
| · The Holocene Epoch may be an interval between glacial incursions, typical of the Pleistocene Epoch and therefore not a separate epoch in itself. · However, it is a period marked by the presence and influence of Homo sapiens. · During this time, the glaciers retreat, sea levels rise, the climate warms, and deserts form in some area | · Human civilization develops. · Activities of mankind begin to affect world climates. · The extinction of other species continues.
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| Pleistocene Epoch
1.6 million-10,000 years ago | · This epoch is best known as the "Great Ice Age." · ce sheets and other glaciers encroach and retreat during four or five primary glacial periods. · At its peak, as much as 30% of the Earth's surface is covered by glaciers, and parts of the northern oceans are frozen. · The movement of the glaciers alters the landscape. · Lakes, such as the Great Lakes in North America, are formed as ice sheets melt, and retreat. · Global warming begins after the last glacial maximum, 18,000 years ago. | · The oldest species of Homo—Homo habilis—evolves. · The flora and fauna in the regions not covered by ice are essentially the same as those of the earlier Pliocene Epoch. · Mammalian evolution includes the development of large forms: woolly mammoth, woolly rhinoceros, musk ox, moose, reindeer, elephant, mastodon, bison, andground sloth. · In the Americas, large mammals, such as horses,camels, mammoths, mastodons, saber-toothed cats, and ground sloths, are entirely extinct by the end of this epoch. |
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| Tertiary Period: Pliocene, Miocene, Oligocene, Eocene, and Paleocene Epochs |
| Time | Geologic Development | Life Forms |
| Pliocene Epoch
5-2 million years ago | · The emergence of the Isthmus of Panama changes ocean circulation patterns and coincides with the formation of an Arctic ice cap. · Plate tectonic interactions result in the uplift of the Sierra Nevada, formation of the Cascade Range · Onset of strike-slip faulting on the San Andreas Fault. · In Europe, the Alps continue to rise. · The global climates become cooler and drier. | · Camels and horses are abundant throughout North America. · Ground sloths also evolve · Primates continue to evolve, and the australopithecines—antecedents to Homo sapiens—develop late in the Pliocene in Africa. · In North America, rhinoceroses and ordeodonts become extinct. |
| Miocene Epoch
25-5 million years ago | · Modern ocean currents are essentially established. · A drop in sea level near the end of the Epoch isolates and dries up the Mediterranean Sea, leaving evaporite deposits on its floor. · The climate is generally cooler than the Oligocene Epoch. · A cold transantarctic ocean current isolates the waters around Antarctica, and the continent becomes permanently frozen. | · Mammal forms are essentially modern, and almost half of modern placental mammal families are present · Almost all the modern groups of whales, birds are present, as well as the early seals and walruses. · Higher primates undergo substantial evolution; advanced primates, including apes, are present in southern Europe and Asia. · On land, grasslands replace forests over large areas on several continents. |
| Oligocene Epoch
38-25 million years ago | · Tectonic plate movement is still very dynamic. · Africa and Europe nearly collide, closing the Tethys Sea and leaving as a remnant the Mediterranean Sea. · Volcanism and fragmentation of western North America is associated with the emplacement of major ore deposits. · The southeren ocean forms · The climate is generally temperate. · Glaciation begins in Antarctica. | · Representatives of modern mammals become the dominant vertebrate life form, including horses, pigs, true carnivores, rhinoceroses, elephants, and camels. · Oreodonts diversify in North America. · Early primates appear in North America, and early apes appear in Egypt. · Many archaic mammals become extinct. · The earliest representatives of modern cetaceans (baleen and "toothed" whales) evolve. · Grasslands expand, and forest regions diminish. |
| Eocene Epoch
55-38 million years ago | · Plate tectonics and volcanic activity form the Rockies in western North America. · Erosion fills basins. · Continental collisions between India and Asia culminate in the Alpine-Himalayan mountain system. · Antarctica and Australia continue to separate and drift apart. · The climate is subtropical and moist throughout North America and Europe. | · Early forms of horse, rhinoceros, camel, and other modern groups such as bats evolve in Europe and North America. · Creodonts and ruminant ungulates evolve. · Archaic whales (archeocetes) evolve from terrestrial meat-eating ungulates. · Sirenians (dugongs and manatees) first evolve in the shallow Tethys Sea. |
| Paleocene Epoch
65-55 million years ago | · During the Paleocene, the vast inland seas of the Cretaceous Period dry up, exposing large land areas in North America and Eurasia. · Australia begins to separate from Antarctica, and Greenland splits from North America. · A remnant Tethys Sea persists in the equatorial region. | · Mammalian life diversifies, spreading into all major environments. · Placental mammals eventually dominate the land, and many differentiated forms evolve, including early ungulates (hoofed animals), primates, rodents, and carnivores. |
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| Mesozoic Era (Middle Life).
Three periods: Cretaceous, Jurassic, and Triassic. |
| Time | Geologic Development | Life Forms |
| Cretaceous Period
144-66 million years ago | · South America and Africa separate. · The Atlantic ocean widens. · A circum-equatorial sea, Tethys, forms between the continents of the Northern and Southern Hemisphere. · The westward movement of North America forms the ancestral Rocky Mountains and the ancestral Sierra Nevada. · Sea levels rise, submerging about 30% of the Earth's present land surface. · The global climate is generally warm. The poles are free of ice. | · Dinosaurs and other large reptiles peak as the dominant vertebrate life form on Earth. · In the shallow seas, invertebrates live in great diversity. Ammonites are a dominant group. · Gastropods, corals, sea urchins flourish. · The early flowering plants (angiosperms), modern trees, and many modern types of insects evolve. · Near the end of the Cretaceous Period, several mass extinctions occur, including the extinction of five major reptilian groups: dinosaurs, pterosaurs, ichthyosaurs, pleisosaurs, and mosasaurs. · Extinctions also occur among ammonites, corals, and other marine invertebrates.
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| Jurassic Period
208-144 million years ago | · The supercontinent of Pangea begins to breakup as North America separates from Eurasia and Africa. · The Atlantic & Indian Ocean begins to form. · Tectonic plate subduction along western North America causes the Earth's crust to fold and mountains form in the western part of the continent. · Gulf of Mexico & Tethys Sea opens · Newark group lava & Caru volcanism | · Reptiles adapt to life in the sea, in the air, and on land. Dinosaurs are the dominant reptile on land. · Archaeopteryx, the first bird, evolves. · Early amphibians, extinct by the late Triassic, are succeeded by the first frogs, toads, and salamanders. · Mammals are small, shrew-like animals. · Plant forms are dominated by the cycads and cycadeoides. · Conifers and gingkoes are widespread. |
| Triassic Period
245-208 million years ago | · Pangaea covers nearly a quarter of the Earth's surface. · Toward the end of the Triassic Period, continental rifting begins to break apart the supercontinent. · The general climate is warm, becoming semiarid to arid. | · Life began to diversify after the end-Permian extinction. · First dinosaurs evolve. · Amphibians in fresh water, retreating. · Primitive mammals appear. · Forests of gymnosperms and ferns. · First modern coral appear. |
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| Paleozoic Era (Ancient Life).
Six periods: Permian, Carboniferous, Devonian, Silurian, Ordovician, Cambrian |
| Time | Geologic Development | Life Forms |
| Permian Period
286-245 million years ago | · A single supercontinent, Pangaea, forms as Earth's landmasses collide and merge. · Pangaea extends across all climatic zones and nearly from one pole to the other. This supercontinent is surrounded by an immense world ocean. · Extensive glaciation persists in what is now India, Australia, and Antarctica. · Hot, dry conditions prevail elsewhere on Pangaea, and salt forming deserts become widespread. · Index Fossil: Fusulinid foraminifera | · Invertebrate marine life is rich and diverse at the beginning of the Permian period. · Toward the end of this period, mass extinctions occur among large groups of corals, bryozoans, arthropods, and other invertebrates. · 99% of all life perishes. · On land, insects evolve into their modern forms; dragonflies and beetles appear. · Amphibians decline in number, but reptiles undergo a spectacular evolutionary development of carnivorous and herbivorous, terrestrial and aquatic forms. · Ferns and conifers persist in the cooler air. |
| Carboniferous Period
360-286 million years ago | · Two major land masses form: Laurasia to the north of the equator, and Gondwana to the south. · Collisions between Laurasia and Gondwana form major mountain ranges. · Coal-forming sediments are laid down in vast swamps. · Global climate changing from warm and wet to cooler and drier | · Age of amphibians. Sharks abundant · First reptiles, Variety of insects. · Great swamps; forests of ferns, gymnosperms (naked seed plants) and horsetails. · 2nd glaciation in Africa, Antarctic & India between Carboniferous to Permian period. |
| Devonian Period
408-360 million years ago | · Europe and North America collide, forming the northern part of the ancestral Appalachian mountain range. · Europe and North America straddle the equator · Africa and South America are positioned over the South Pole. · The climate is generally warm and moist. · Marked by Acadian Orogeny · Catskill Delta | · This period is called Age of fishes—armored fish, lungfish, and sharks. · Ammonites evolve from nautiloids and become one of the dominant invertebrate forms. · As the ozone layer forms, the first air-breathing arthropods—spiders and mites—evolve on land. · First Amphibians evolve and venture onto land.
First seed producing Plants including lowland forests of giant psilophyta plants develop and spread over the planet. |
| Silurian Period
438-408 million years ago | · The North American, European, and Asian land masses are situated on or near the equator. · Laurentia and Baltica collide. · Mountain building in Europe. · Gondwana sits in the South Polar Region. · Shallow flooding of continental areas deposits sediments · Later withdrawal of ocean water leaves oxidized "red beds" and extensive salt deposits. · Extensive Shallow sea over The Sahara · Clinton Iron formation in S. Appalachian | · Shell-forming sea animals abundant. · Rise of Fishes( placoderms) · First Shark · Sea lilies (stalked crinoids), eurypterids, land scorpions. · Invasion of land by arthropods. · Earliest vascular plants (psilopsids, lycophytes). · Modern groups of algae and fungi. |
| Ordovician Period
505-438 million years ago | · The barren continents of Laurentia, Baltica, Siberia, and Gondwana are separated by large oceans. · Shallow seas cover much of North America at the beginning of the period. · As the seas recede, they leave a thick layer of limestone. · Later in the period, the seas recover North America, depositing quartz, sandstones, and more limestone. · Beginning of Appalachian mountain. · The global climate is generally mild. | · Coral reefs developed · Agnatha (no jaw fishes, first vertebrates). · First primitive fishes (ostracoderms, vertebrates). · Invertebrates dominant. Crustaceans, trilobites, graptolites, brachiopods, bryozoa, echinoderms, corals, mollusks, cephalopods. · First fungi. · Possible invasions of land by plants. |
| Cambrian Period
540-505 million years ago | · Sedimentary rocks (sandstone, shale, limestone, conglomerate) form in shallow seas over the continents. · Rodinia begins to break up into northern and southern portions. · Extensive Seas in major Synclines · Much volcanic activity & Long period of marine Sedimentation · The global climate is generally mild. · Pan African orogeny occurred · First Glaciations Cambrian to Ordovician period in Africa. | · Marine metazoans with mineralized skeletons, such as sponges, bryozoans, corals, brachiopods, molluscs, arthropods, and echinoderms, flourish. · The trilobites are particularly dominant in the shallow-water marine habitats. · Trilobites & Agnathids made up 60% of Cambrian fossils · Plant life is limited to marine algae. · First Shelled marine invertebrates · Another important Index fossil is The Archeocyathiels. |
| Precambrian Time. Three Eons: Proterozoic, Archean, and Hadean. |
| Time | Geologic Development | Life Forms |
| Proterozoic Eon
2.5 billion years ago-538 million years ago | · The supercontinent Rodinia forms approximately 1.1 billion years ago. · Plate tectonics slows to approximately the same rate as the present. · Large mountain chains form as the continents collide. · Quartz-rich sandstones, shales, and limestones are deposited over the continents. · Oxygen levels increase as life on Earth develops the ability to obtain energy through photosynthesis. · The late Proterozoic is an "Ice House" world. | · Eukaryotes (single-celled organisms with a nucleus) evolve · These are more advanced forms of algae and a wide variety of protozoa. · Eukaryotes can reproduce sexually, which makes genetic diversity possible, as well as the ability to adapt to and survive environmental changes. · Multi-celled, soft-bodied marine organisms (metazoans) evolve. |
| Archean Eon
3.8-2.5 billion years ago | · The Earth's permanent crust is formed. · Vast amounts of metallic minerals are deposited. · The oceans and atmosphere result from volcanic out gassing. | · The earliest life forms evolve in the seas. · They are the prokaryotes—single-celled organisms with no nucleus—cyanobacteria (blue-green algae). · The earliest bacteria obtain energy through chemosynthesis (ingestion of organic molecules). |
| Hadean Eon (Azoic)
4.6-3.8 billion years ago | · The Earth forms as a solid planet. | · No evidence of life yet known. |
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