Fossils & Geologic Time Portal

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<nav class="breadcrumb justify-content-center"> <span class="breadcrumb-item "> <a href="/" class="link-white">Home</a> </span> <span class="breadcrumb-item "> <a class="link-white" href="/browse/Science">Science</a> </span> <span class="breadcrumb-item "> <a class="link-white" href="/browse/Earth-Science-Geology-Fossils">Earth Science, Geologic Time & Fossils</a> </span> <span class="breadcrumb-item "> Fossils & Geologic Time </span> </nav> <h1 class="font-serif mt-30 mb-20">Fossils & Geologic Time</h1> <div class="font-serif grid"> <div class="col-sm-70 col-sm-offset-15"> Geologic time is the extensive interval of time occupied by the geologic history of Earth. Formal geologic time begins at the start of the Archean Eon (4.0 billion to 2.5 billion years ago) and continues to the present day.</div> </div> </div> </div> <div class="container"> <h2 class="label my-30">Fossils & Geologic Time Encyclopedia Articles</h2> <div class="grid top g-10 mb-40"> <div class="col-33 col-sm-20 col-md-16 col-lg-10"> <div class="border shadow p-10 text-center "> <a class="font-weight-bold font-14 " href="/browse/Fossil-Geologic-Time/1">ACH-CAS</a> </div> </div> <div class="col-33 col-sm-20 col-md-16 col-lg-10"> <div class="border shadow p-10 text-center "> <a class="font-weight-bold font-14 " href="/browse/Fossil-Geologic-Time/2">CAU-EIS</a> </div> </div> <div class="col-33 col-sm-20 col-md-16 col-lg-10"> <div class="border shadow p-10 text-center "> <a class="font-weight-bold font-14 " href="/browse/Fossil-Geologic-Time/3">ELE-LAM</a> </div> </div> <div class="col-33 col-sm-20 col-md-16 col-lg-10"> <div class="border shadow p-10 text-center "> <a class="font-weight-bold font-14 " href="/browse/Fossil-Geologic-Time/4">LAR-PAL</a> </div> </div> <div class="col-33 col-sm-20 col-md-16 col-lg-10"> <div class="border shadow p-10 text-center "> <a class="font-weight-bold font-14 " href="/browse/Fossil-Geologic-Time/5">PAL-SIM</a> </div> </div> <div class="col-33 col-sm-20 col-md-16 col-lg-10"> <div class="border shadow p-10 text-center "> <a class="font-weight-bold font-14 " href="/browse/Fossil-Geologic-Time/6">SIM-ZIT</a> </div> </div> </div> <h2 class="label my-30 text-center">Featured Articles</h2> <div class="js-pinboard grid gy-20"> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/science/Ordovician-Period" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/38/136138-050-725FA2B8/Distribution-landmasses-regions-seas-ocean-basins-Ordovician.jpg?w=400&h=225&c=crop" alt="Ordovician paleogeography" class="col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/science/Ordovician-Period" class="font-weight-bold font-16 lh-sm">Ordovician Period</a> <div class="font-serif mt-10 font-14"> Ordovician Period, in geologic time, the second period of the Paleozoic Era. It began 485.4 million years ago, following the Cambrian Period, and ended 443.8 million years ago, when the Silurian Period... </div> </div> </div> </div> </div> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/animal/dinosaur" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/50/8050-050-D930CD43/Mesozoic-Era-Age-of-Dinosaurs-periods-dinosaurs.jpg?w=400&h=225&c=crop" alt="dinosaurs to scale" class="col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/animal/dinosaur" class="font-weight-bold font-16 lh-sm">dinosaur</a> <div class="font-serif mt-10 font-14"> Dinosaur, (clade Dinosauria), the common name given to a group of reptiles, often very large, that first appeared roughly 245 million years ago (near the beginning of the Middle Triassic Epoch) and thrived... </div> </div> </div> </div> </div> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/science/fossil" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/05/77405-004-D48C88DA/footprint-dinosaur.jpg?w=400&h=225&c=crop" alt="fossil" class="col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/science/fossil" class="font-weight-bold font-16 lh-sm">fossil</a> <div class="font-serif mt-10 font-14"> Fossil, remnant, impression, or trace of an animal or plant of a past geologic age that has been preserved in Earth鈥檚 crust. The complex of data recorded in fossils worldwide鈥攌nown as the fossil record鈥攊s... </div> </div> </div> </div> </div> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/science/geochronology" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/86/106986-050-0119C0F2/Grand-Canyon-wall-cutaway-diagram-rock-layers.jpg?w=400&h=225&c=crop" alt="Grand Canyon rock layering" class="col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/science/geochronology" class="font-weight-bold font-16 lh-sm">geochronology</a> <div class="font-serif mt-10 font-14"> Geochronology, field of scientific investigation concerned with determining the age and history of Earth鈥檚 rocks and rock assemblages. Such time determinations are made and the record of past geologic... </div> </div> </div> </div> </div> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/science/Silurian-Period" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/37/136137-050-83DF315F/Distribution-landmasses-regions-seas-part-ocean-basins.jpg?w=400&h=225&c=crop" alt="Silurian paleogeography" class="col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/science/Silurian-Period" class="font-weight-bold font-16 lh-sm">Silurian Period</a> <div class="font-serif mt-10 font-14"> Silurian Period, in geologic time, the third period of the Paleozoic Era. It began 443.8 million years ago and ended 419.2 million years ago, extending from the close of the Ordovician Period to the beginning... </div> </div> </div> </div> </div> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/science/Carboniferous-Period" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/47/136147-050-F0548F0D/Distribution-landmasses-regions-seas-ocean-basins-locations.jpg?w=400&h=225&c=crop" alt="Carboniferous paleogeography" class="col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/science/Carboniferous-Period" class="font-weight-bold font-16 lh-sm">Carboniferous Period</a> <div class="font-serif mt-10 font-14"> Carboniferous Period, fifth interval of the Paleozoic Era, succeeding the Devonian Period and preceding the Permian Period. In terms of absolute time, the Carboniferous Period began approximately 358.9... </div> </div> </div> </div> </div> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/science/Holocene-Epoch" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/67/73167-050-C66534D1/chart.jpg?w=400&h=225&c=crop" alt="geologic time" class="col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/science/Holocene-Epoch" class="font-weight-bold font-16 lh-sm">Holocene Epoch</a> <div class="font-serif mt-10 font-14"> Holocene Epoch, younger of the two formally recognized epochs that constitute the Quaternary Period and the latest interval of geologic time, covering approximately the last 11,700 years of Earth鈥檚 history.... </div> </div> </div> </div> </div> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/science/Jurassic-Period" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/45/136145-050-0AC28C9A/Distribution-landmasses-regions-seas-ocean-basins-locations.jpg?w=400&h=225&c=crop" alt="Jurassic paleogeography" class="col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/science/Jurassic-Period" class="font-weight-bold font-16 lh-sm">Jurassic Period</a> <div class="font-serif mt-10 font-14"> Jurassic Period, second of three periods of the Mesozoic Era. Extending from 201.3 million to 145 million years ago, it immediately followed the Triassic Period (251.9 million to 201.3 million years ago)... </div> </div> </div> </div> </div> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/science/Pleistocene-Epoch" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/60/226660-050-A0E159F0/ice-age-Cordilleran-Laurentide-greenland-ice-sheet-North-America.jpg?w=400&h=225&c=crop" alt="Wisconsin glaciation" class="col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/science/Pleistocene-Epoch" class="font-weight-bold font-16 lh-sm">Pleistocene Epoch</a> <div class="font-serif mt-10 font-14"> Pleistocene Epoch, earlier and major of the two epochs that constitute the Quaternary Period of Earth鈥檚 history, an epoch during which a succession of glacial and interglacial climatic cycles occurred.... </div> </div> </div> </div> </div> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/science/Cretaceous-Period" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/44/136144-050-200CA3A5/Distribution-landmasses-regions-seas-ocean-basins-Cretaceous.jpg?w=400&h=225&c=crop" alt="Cretaceous paleogeography" class="col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/science/Cretaceous-Period" class="font-weight-bold font-16 lh-sm">Cretaceous Period</a> <div class="font-serif mt-10 font-14"> Cretaceous Period, in geologic time, the last of the three periods of the Mesozoic Era. The Cretaceous began 145.0 million years ago and ended 66 million years ago; it followed the Jurassic Period and... </div> </div> </div> </div> </div> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/science/Tertiary-Period" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/22/148022-050-CA2C991E/Gypsum-cones-evaporation-basin-Mediterranean-Sea-Sorbas.jpg?w=400&h=225&c=crop" alt="Messinian Stage" class="col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/science/Tertiary-Period" class="font-weight-bold font-16 lh-sm">Tertiary Period</a> <div class="font-serif mt-10 font-14"> Tertiary Period, former official interval of geologic time lasting from approximately 66 million to 2.6 million years ago. It is the traditional name for the first of two periods in the Cenozoic Era (66... </div> </div> </div> </div> </div> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/science/Quaternary" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/50/136150-050-BC0EEAA7/Distribution-landmasses-regions-seas-ocean-basins-locations.jpg?w=400&h=225&c=crop" alt="Quaternary paleogeography" class="col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/science/Quaternary" class="font-weight-bold font-16 lh-sm">Quaternary</a> <div class="font-serif mt-10 font-14"> Quaternary, in the geologic history of Earth, a unit of time within the Cenozoic Era, beginning 2,588,000 years ago and continuing to the present day. The Quaternary has been characterized by several periods... </div> </div> </div> </div> </div> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/science/Devonian-Period" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/48/136148-050-381060F0/Distribution-landmasses-regions-seas-ocean-basins-locations.jpg?w=400&h=225&c=crop" alt="Devonian paleogeography" class="col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/science/Devonian-Period" class="font-weight-bold font-16 lh-sm">Devonian Period</a> <div class="font-serif mt-10 font-14"> Devonian Period, in geologic time, an interval of the Paleozoic Era that follows the Silurian Period and precedes the Carboniferous Period, spanning between about 419.2 million and 358.9 million years... </div> </div> </div> </div> </div> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/science/Cambrian-Period" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/39/136139-050-F14C623B/Distribution-landmasses-regions-seas-ocean-basins-Cambrian.jpg?w=400&h=225&c=crop" alt="Cambrian paleogeography" class="col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/science/Cambrian-Period" class="font-weight-bold font-16 lh-sm">Cambrian Period</a> <div class="font-serif mt-10 font-14"> Cambrian Period, earliest time division of the Paleozoic Era, extending from 538.8 million to 485.4 million years ago. The Cambrian Period is divided into four stratigraphic series: the Terreneuvian Series... </div> </div> </div> </div> </div> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/topic/Australopithecus" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/37/79537-050-D822C2E7/Australopithecus-afarensis-rendering-Artist.jpg?w=400&h=225&c=crop" alt="Australopithecus afarensis" class="col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/topic/Australopithecus" class="font-weight-bold font-16 lh-sm">Australopithecus</a> <div class="font-serif mt-10 font-14"> Australopithecus, (genus Australopithecus), group of extinct primates closely related to, if not actually ancestors of, modern human beings and known from a series of fossils found at numerous sites in... </div> </div> </div> </div> </div> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/science/Precambrian" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/67/73167-050-C66534D1/chart.jpg?w=400&h=225&c=crop" alt="geologic time" class="col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/science/Precambrian" class="font-weight-bold font-16 lh-sm">Precambrian</a> <div class="font-serif mt-10 font-14"> Precambrian, period of time extending from about 4.6 billion years ago (the point at which Earth began to form) to the beginning of the Cambrian Period, 541 million years ago. The Precambrian encompasses... </div> </div> </div> </div> </div> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/science/Permian-Period" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/49/136149-050-C031C75E/Distribution-landmasses-regions-seas-ocean-basins-Permian.jpg?w=400&h=225&c=crop" alt="Permian paleogeography" class="col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/science/Permian-Period" class="font-weight-bold font-16 lh-sm">Permian Period</a> <div class="font-serif mt-10 font-14"> Permian Period, in geologic time, the last period of the Paleozoic Era. The Permian Period began 298.9 million years ago and ended 252.2 million years ago, extending from the close of the Carboniferous... </div> </div> </div> </div> </div> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/topic/Homo-erectus" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/38/79538-050-6D89C9E3/Homo-erectus-rendering-Artist.jpg?w=400&h=225&c=crop" alt="illustration of Homo erectus" class="col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/topic/Homo-erectus" class="font-weight-bold font-16 lh-sm">Homo erectus</a> <div class="font-serif mt-10 font-14"> Homo erectus, extinct species of the human genus (Homo), perhaps an ancestor of modern humans (Homo sapiens). H. erectus most likely originated in Africa, though Eurasia cannot be ruled out. Regardless... </div> </div> </div> </div> </div> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/science/geologic-time" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/67/73167-050-C66534D1/chart.jpg?w=400&h=225&c=crop" alt="geologic time" class="col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/science/geologic-time" class="font-weight-bold font-16 lh-sm">geologic time</a> <div class="font-serif mt-10 font-14"> Geologic time, the extensive interval of time occupied by the geologic history of Earth. Formal geologic time begins at the start of the Archean Eon (4.0 billion to 2.5 billion years ago) and continues... </div> </div> </div> </div> </div> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/science/dating-geochronology" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/79/143879-004-C683ADF2/strata-outcropping-side-Morrison-Formation-Denver-Colorado.jpg?w=400&h=225&c=crop" alt="Morrison Formation" class="col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/science/dating-geochronology" class="font-weight-bold font-16 lh-sm">dating</a> <div class="font-serif mt-10 font-14"> Dating, in geology, determining a chronology or calendar of events in the history of Earth, using to a large degree the evidence of organic evolution in the sedimentary rocks accumulated through geologic... </div> </div> </div> </div> </div> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/biography/Charles-Darwin" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/30/19630-120-CE960DDD/Charles-Darwin-photograph-Julia-Margaret-Cameron-1868.jpg?w=400&h=225&c=crop" alt="Charles Darwin" class="col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/biography/Charles-Darwin" class="font-weight-bold font-16 lh-sm">Charles Darwin</a> <div class="font-serif mt-10 font-14"> Charles Darwin was an English naturalist whose scientific theory of evolution by natural selection became the foundation of modern evolutionary studies. An affable country gentleman, Darwin at first shocked... </div> </div> </div> </div> </div> <div class="p-10 d-inline-flex js-pin col-100 col-sm-33 col-md-25 "> <div class="card text-normal col-100 "> <div class="card-media position-relative"> <a href="https://www.britannica.com/science/Triassic-Period" style="--aspect-ratio: 16/9"> <img loading="lazy" src="https://cdn.britannica.com/46/136146-050-AC38F468/Distribution-landmasses-regions-seas-ocean-basins-locations.jpg?w=400&h=225&c=crop" alt="Triassic paleogeography" class="col-100" /> </a> </div> <div class="col"> <div class="card-body text-hyphenate"> <a href="https://www.britannica.com/science/Triassic-Period" class="font-weight-bold font-16 lh-sm">Triassic Period</a> <div class="font-serif mt-10 font-14"> Triassic Period, in geologic time, the first period of the Mesozoic Era. 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