Timeline by Amanda Carroll

Phanerozoic Eon: 540mya

car90971 — 2024-06-11 01:24:57 UTC

Time prior to this was known as the PreCambrian, where bacteria and algae evolved into prokaryotes and eukaryotes, producing oxygen via photosynthesis, and setting the stage for the development of life.

Paleozoic Era, 541-252 mya

car90971 — 2024-06-11 01:31:55 UTC

This era is subdivided into 6 periods: the Cambrian, Ordovician, Silurian, Devonian, Mississippian, Pennsylvanian, and Permian.

Cambrian Period, 541-485 mya

car90971 — 2024-06-11 01:36:51 UTC

Warm oceans cover most of North America. Marine invertebrates, early shelled organisms, and coral dominate. Oxygen levels continue to rise.

Ordovician Period, 485-443 mya

car90971 — 2024-06-11 01:43:34 UTC

4 main continents arise: Laurentia, Gondwana, Baltica, and Siberia. Brachiopods, trilobites, and corals dominate, but bony fish begin here. Mountains form on Earth.

Ordovician-Silurian Mass Extinction

car90971 — 2024-06-11 01:49:28 UTC

Approximately 85% of species went extinct. Factors that contributed to this extinction include: falling sea levels, decreases carbon dioxide due to silicate erosion, changes to ocean currents, and the glaciation of South American and African parts of Gondwana. This represents the 2nd largest mass extinction event in history.

Silurian Period, 443-419 mya

car90971 — 2024-06-11 01:53:00 UTC

Ozone layer begins to develop, which helped stabilize Earth's climate. Fish evolve and diversify, jawed fish become present. Plants begin to appear on land.

Devonian Period, 419-358 mya

car90971 — 2024-06-11 01:56:16 UTC

Known as "The Age of the Fishes." On land, plant species diversify, and the first forests (evergreens) are formed. Insects, spiders, and the first tetrapods appear.

Devonian Mass Extinction

car90971 — 2024-06-11 02:06:28 UTC

Mass extinction event primarily involving marine life. Anoxic conditions in the oceans are to blame. One reason for this may be the explosion in plant life, leading to weathering of rocks and creation of soils, whose nutrients may have caused eutrophication and anoxia in the oceans. Global cooling and volcanism are also thought to have contributed to this extinction.

Mississippian Periods, 358-323 mya

car90971 — 2024-06-11 02:11:56 UTC

The first half of the Carboniferous Period. Referred to as the "Age of Crinoids," due to the abundance of their fossils in limestone from the period. Amphibians appear.

Pennsylvanian Period, 232-298 mya

car90971 — 2024-06-11 02:18:49 UTC

Second half of the Carboniferous Period, referred to as the "Age of the Amphibians;" amniotes (egg-layers) divorced reproductive needs from water sources and the sea. Swamp forests and terrestrial habitats become widely distributed, later becoming coal deposits.

Permian Period, 289-251 mya

car90971 — 2024-06-11 02:23:20 UTC

Pangea forms, surrounded by the Panthalassa Ocean. The Appalachian Mountains rise. Reptiles become the dominant life form, amphibians are present in large numbers. Brachiopods, gastropods, cephalopods, and crinoids fill the oceans.

Permian Extinction Event

car90971 — 2024-06-11 02:34:25 UTC

Also called "The Great Dying," 90% of Earth's species were lost; less than 5% of ocean life survived, approximately 1/3 of land animals, and nearly all trees died. Believed to be caused by a massive volcanic eruption in Siberia, creating basalt flows and the Siberian Traps. This release increased sulfur dioxide and carbon dioxide in the oceans, depriving marine species of oxygen and acidifying the oceanic environment. Atmospheric carbon dioxide also increased, and global temperatures rose. Methan emissions and burning were another contributing factor, and a meteor may have also played a role.

Mesozoic Era

car90971 — 2024-06-11 02:37:25 UTC

The Mesozoic Era encompasses the Triassic, Jurassic, and Cretaceous periods, seeing the rise and fall of dinosaurs, as well as the beginning of the rise of mammals.

Triassic Period, 251-201 mya

car90971 — 2024-06-11 02:42:18 UTC

Pangaea begins to break up into modern continents. The first dinosaurs and mammals begin to appear. Flying reptiles begin to appear. This is the beginning of the "Age of Reptiles." Plant life continues to diversify.

Triassic Extinction Event

car90971 — 2024-06-11 02:55:17 UTC

Archosauromorphs and large amphibians became extinct, as did between 25-35% of marine species. Plant species also experienced a decline, although not as significant as the animals did. Contributing factors include: sea level fall, climate change, volcanism, impacts from comets or asteroids, ocean acidification, and metal poisoning from mercury released during volcanic eruptions.

Jurassic Period, 201-145 mya

car90971 — 2024-06-11 02:59:09 UTC

A wide variety of dinosaurs flourish. The first birds appear. Pangaea continues to break apart.

Cretaceous Period, 145-66 mya

car90971 — 2024-06-11 03:05:23 UTC

During the Cretaceous period, flowering plants appear and diversify. The first snakes and primates appear. Rocky Mountains begin to rise. Placental mammals arrive on the scene.

Cretaceous Extinction Event

car90971 — 2024-06-11 03:12:09 UTC

The end of the Cretaceous period is marked by another mass extinction, the largest ever recorded. Creatures on land, in the air, and in the ocean were devastated. Dinosaurs, most tetrapods over 55lbs., mammals, birds, lizards, insects, plants, marine plankton, marine organisms, and all pterosaurs were lost. 3/4 of life on Earth ceased to exist. This was a global event thought to be caused by an asteroid impact, which correlates to a layer of iridium found in sediment deposits world-wide dating to this time frame.

Cenozoic Era, 66mya-Present Day.

car90971 — 2024-06-11 03:14:27 UTC

The Cenozoic Ear is divided into 3 periods: the Paleogene, Neogene, and Quaternary periods. It is referred to as the Age of Mammals.

Paleogene Period, 66-56mya

car90971 — 2024-06-11 03:26:23 UTC

North America begins drying up, sea levels are rising. the beginning of the period is marked by small mammals, and by the mid-Paleocene, ungulates become abundant. Grasses become widespread; flora diversifies to include pines, cacti, and palms. Early primates appear, including tarsiers and tree shrews. Mammal species diversify and include: dogs, cats, horses, rhinos, camels, tapir, and megafauna, including giant sloths, saber toothed cats, mastodons, giant beavers, and giant armadillos.

Neogene Period, 23-2.6 mya

car90971 — 2024-06-11 03:32:22 UTC

Global cooling leads to a decrease in forests and an increase in grasslands. Mammals and birds continue to evolve and diversify, notably, horses. The landscape of North America changes, becomes wetter and connected to South America, allowing animal species to move between continents. The climate continues to cool.

Quaternary Period, 2.6mya-Present Day.

car90971 — 2024-06-11 03:38:57 UTC

This period is characterized by periods of glacial growth and retreat, including the Ice Age, covering the Earth in sheets of ice, lowering sea levels so that land bridges, such as the Bering Strait, become navigable, allowing humans to migrate from Asia to North America. Modern humans develop and proliferate. Megafauna becomes extinct. Human civilization leads to industrialization, increasing atmospheric carbon dioxide levels leading to global warming, and perhaps the 6th great extinction event.