geological time by:dk

4000 to 2500,During the Archean Eon, methane droplets in the air shrouded the young Earth in a global haze. ... 2.7 billion years ago, bluish-green microscopic organisms called cyanobacteria flourished in Earth's oceans.

Underwater life thrived during the Silurian Period, 443 million years ago to 416 million years ago. The Paleozoic Era, which ran from about 542 million years ago to 251 million

299 to 251 million years ago.he Permian period, which ended in the largest mass extinction the Earth has ever known, began about 299 million years ago.

The Silurian Period occurred from 443 million to 416 million years ago. It was the third period in the Paleozoic Era. It followed the Ordovician Period and preceded the Devonian Period.

The dinosaurs and the mammals appeared during the Triassic period, roughly 225 million years ago. The dinosaurs went extinct 65 million years ago.The Mesozoic Era lasted about 180 million years, and is divided into three periods, the Triassic, the Jurassic, and the Cretaceous.

Following the Paleozoic, the Mesozoic extended roughly 186 million years, from 252.17 to 66 million years ago when the Cenozoic Era began.

199.6 to 145.5 million years ago

The largest dinosaurs of the time -- in fact, the largest land animals of all time -- were the gigantic sauropods, such as the famous Diplodocus (pictured at lower left), Brachiosaurus and Apatosaurus.

66 million to 23 million years ago, the Neogene 23 million to 2.6 million years ago), and the Quaternary 2.6 million years ago to the present.

The Cenozoic Era, which began about 65 million years ago and continues into the present, is the third documented era in the history of Earth.Quaternary Period 2.6 million years ago to the present), consisting the Pleistocene and Holocene epochs.The Cenozoic Era, which began about 65 million years ago and continues into the present, is the third documented era in the history of Earth. The current locations of the continents and their modern-day inhabitants, including humans, can be traced to this period

The Oligocene Epoch, right smack in the middle of the Tertiary Period (and end of the Paleogene), lasted from about 33.9 to 23 million years ago.* Although it lasted a "short" 11 million years, a number of major changes occurred during this time. These changes include the appearance of the first elephants with trunks, early horses, and the appearance of many grasses — plants that would produce extensive grasslands in the following epoch, the Miocene.

  • The Pliocene, 5.3 to 2.6 million years ago,* was a time of global cooling after the warmer Miocene. The cooling and drying of the global environment may have contributed to the enormous spread of grasslands and savannas during this time. The change in vegetation undoubtedly was a major factor in the rise of long-legged grazers who came to live in these areas.

The Holocene Epoch is the current period of geologic time. Another term that is sometimes used is the Anthropocene Epoch, because its primary characteristic is the global changes caused by human activity. This term can be misleading, though; modern humans were already well established long before the epoch began. The Holocene Epoch began 12,000 to 11,500 years ago at the close of the Paleolithic Ice Age and continues through today.

Created By
Deshaun Keith


Created with images by Darren Shilson - "Roche Rock Redux" • NASA Goddard Photo and Video - "Blue Marble 2000" • Trailmix.Net - "Trilobite" • James St. John - "Helicoprion fossil shark reconstruction (Permian) 1" • James St. John - "Sthenarocalymene celebra fossil trilobite (Cedarville Dolomite, Middle Silurian; Preble County, southwestern Ohio, USA)" • BioDivLibrary - "n90_w1150" • James St. John - "Dasypus novemcinctus skeleton (nine-banded armadillo) 1" • Blacren - "Jurassic" • James St. John - "Nimravus major (fossil false sabertooth mammal with canine tooth piercing another bone) (Oligocene; Black Hank Canyon, Wildcat Hills, Nebraska, USA) 3" • James St. John - "Ursus spelaeus (cave bear) (Pleistocene; France) 3" • James St. John - "Paranthropus boisei fossil hominid (Koobi Fora Formation, Lower Pleistocene, 1.75 Ma; Olduvai Gorge, western Arusha Region, northern Tanzania, eastern Africa) 1" • James St. John - "Lambis scorpius (scorpion spider conch) 2"

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