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Geologic time scale

Geologic time scale
The geologic time scale (GTS) is a system of chronological measurement that relates stratigraphy to time, and is used by geologists, paleontologists, and other earth scientists to describe the timing and relationships between events that have occurred throughout Earth's history. The table of geologic time spans presented here agrees with the nomenclature, dates and standard color codes set forth by the International Commission on Stratigraphy. Evidence from radiometric dating indicates that the Earth is about 4.54 billion years old. The geology or deep time of Earth's past has been organized into various units according to events which took place in each period. Different spans of time on the GTS are usually delimited by changes in the composition of strata which correspond to them, indicating major geological or paleontological events, such as mass extinctions. Terminology[edit] History and nomenclature of the time scale[edit] Graphical representation of Earth's history as a spiral

Homo habilis Homo habilis (also Australopithecus habilis) is a species of the Hominini tribe, which lived from approximately 2.33 to 1.44 million years ago, during the Gelasian Pleistocene period.[1] While there has been scholarly controversy regarding its placement in the genus Homo rather than the genus Australopithecus,[2][3] its brain size has been shown to range from 550 cm3 to 687 cm3, rather than from 363 cm3 to 600 cm3 as formerly thought.[3][4] These more recent findings concerning brain size favor its traditional placement in the genus Homo, as does the need for the genus to be monophyletic if H. habilis is indeed the common ancestor.[citation needed] Homo habilis has often been thought to be the ancestor of the more gracile and sophisticated Homo ergaster, which in turn gave rise to the more human-appearing species, Homo erectus. Findings[edit] KNM ER 1813[edit] OH 7[edit] OH 24[edit] KNM ER 1805[edit] Interpretations[edit] Homo habilis - Forensic facial reconstruction/approximation Notes[edit]

Grand Canyon Lava Flows: A Survey of Isotope Dating Methods Do analyses of the radioactive isotopes of rocks give reliable estimates of their ages? That is a good question, which ordinarily requires a lengthy and technical answer. In order to give an initial response, we might confine our attention to dating of lava flows, the most easily dated rocks, and limit our discussion to the Grand Canyon, which contains thoroughly studied lava flows profoundly relevant to the creation/evolution question. Furthermore, we might begin by focusing our investigation to "wholerock" potassium-argon (K-Ar) and rubidium-strontium (Rb-Sr) techniques, the two most popular methods for dating rocks. Popular Dating Methods Both the K-Ar and Rb-Sr methods make use of radioactive decay of a parent isotope to a stable daughter isotope. 87 S r p = 87 Sr o + 87 Rb p (e lt -1) & nbsp; (1) The analytical equipment used to determine the abundances of isotopes is more accurate in determining ratios of isotopes than their absolute abundances. Grand Canyon Lava Flows 1. * Dr.

Geological history of Earth Geologic time represented in a diagram called a geological clock, showing the relative lengths of the eons of Earth's history and noting major events The geological history of Earth follows the major events in Earth's past based on the geologic time scale, a system of chronological measurement based on the study of the planet's rock layers (stratigraphy). Earth formed about 4.54 billion years ago by accretion from the solar nebula, a disk-shaped mass of dust and gas left over from the formation of the Sun, which also created the rest of the Solar System. As the surface continually reshaped itself over hundreds of millions of years, continents formed and broke apart. The present pattern of ice ages began about 40 million years ago, then intensified at the end of the Pliocene. Precambrian[edit] The Precambrian includes approximately 90% of geologic time. Hadean Eon[edit] Archean Eon[edit] By 3.5 billion years ago, the Earth's magnetic field was established. Proterozoic Eon[edit]

Homo gautengensis Homo gautengensis is a hominin species proposed by biological anthropologist Darren Curnoe in 2010. The species is composed of South African hominin fossils previously attributed to Homo habilis, Homo ergaster or in some cases Australopithecus and is argued by Curnoe to be the earliest species in the genus Homo.[1] Discovery and analysis[edit] Analysis announced in May 2010 of a partial skull found decades earlier in South Africa's Sterkfontein Caves in Gauteng near Johannesburg identified the species, named Homo gautengensis by anthropologist Dr. Geochronology[edit] Identification of H. gautengensis was based on partial skulls, several jaws, teeth and other bones found at various times and cave sites in the Cradle of Humankind. Description[edit] Curnoe believes H. gautengensis stood just over 3 feet (0.91 m) tall and weighed about 110 pounds (50 kg). The researchers believe it lacked speech and language skills. Implications[edit] See also[edit] References[edit]

Mesozoic The Mesozoic era /mɛzɵˈzoʊɪk/ is an interval of geological time from about 252 to 66 million years ago. It is also called the age of reptiles, a phrase introduced by the 19th century paleontologist Gideon Mantell who viewed it as dominated by reptiles such as Iguanadon, Megalosaurus, Plesiosaurus and what are now called Pseudosuchia.[1] The era began in the wake of the Permian–Triassic extinction event, the largest well-documented mass extinction in Earth's history, and ended with the Cretaceous–Paleogene extinction event, another mass extinction which is known for having killed off non-avian dinosaurs, as well as other plant and animal species. Geologic periods[edit] The lower (Triassic) boundary is set by the Permian–Triassic extinction event, during which approximately 90% to 96% of marine species and 70% of terrestrial vertebrates became extinct.[3] It is also known as the "Great Dying" because it is considered the largest mass extinction in the Earth's history. Climate[edit]

Homo rudolfensis Homo rudolfensis (also Australopithecus rudolfensis) is an extinct species of the Hominini tribe known only through a handful of representative fossils, the first of which was discovered by Bernard Ngeneo, a member of a team led by anthropologist Richard Leakey and zoologist Meave Leakey in 1972, at Koobi Fora on the east side of Lake Rudolf (now Lake Turkana) in Kenya. On 8 August 2012, a team led by Meave Leakey announced the discovery of a face and two jawbones belonging to H. rudolfensis. KNM-ER 1470[edit] UR 501 (original specimen), the oldest fossil of genus Homo The fossil KNM-ER 1470 was the center of much debate concerning its species. In March 2007, a team led by Timothy Bromage, an anthropologist at New York University, reconstructed the skull of KNM-ER 1470. 2012 fossil find[edit] See also[edit] References[edit] ^ Jump up to: a b В.П. External links[edit]

Cretaceous The Cretaceous (/krɨˈteɪʃəs/, krə-TAY-shəs), derived from the Latin "creta" (chalk), usually abbreviated K for its German translation Kreide (chalk), is a geologic period and system from circa 145 ± 4 to 66 million years (Ma) ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the Cenozoic era. It is the last period of the Mesozoic Era, and, spanning 79 million years, the longest period of the Phanerozoic Eon. Geology[edit] Key events in the Cretaceous An approximate timescale of key Cretaceous events. Research history[edit] Stratigraphic subdivisions[edit] As with other older geologic periods, the rock beds of the Cretaceous are well identified but the exact ages of the system's base is uncertain by a few million years. Rock formations[edit] The high eustatic sea level and warm climate of the Cretaceous meant a large area of the continents was covered by warm shallow seas. Paleogeography[edit] Climate[edit] Life[edit]

Hominidae The Hominidae (/hɒˈmɪnɨdiː/; also known as great apes[notes 1]) form a taxonomic family of primates, including four extant genera: The term "hominid" is also used in the more restricted sense as hominins or "humans and relatives of humans closer than chimpanzees".[2] In this usage, all hominid species other than Homo sapiens are extinct. A number of known extinct genera are grouped with humans in the Homininae subfamily, others with orangutans in the Ponginae subfamily. History[edit] Species close to the last common ancestor of gorillas, chimpanzees, bonobos and humans may be represented by Nakalipithecus fossils found in Kenya and Ouranopithecus found in Greece. Taxonomic history[edit] The classification of the great apes has been revised several times in the last few decades. The primatological term hominid is easily confused with a number of very similar words: Especially close human relatives form a subfamily, the Homininae. Classification[edit] Extant[edit] Fossil[edit] Family Hominidae

Jurassic Etymology[edit] The chronostratigraphic term "Jurassic" is directly linked to the Jura Mountains. Alexander von Humboldt recognized the mainly limestone dominated mountain range of the Jura Mountains as a separate formation that had not been included in the established stratigraphic system defined by Abraham Gottlob Werner, and he named it "Jurakalk" in 1795.[4][5][6][7] The name "Jura" is derived from the Celtic root "jor", which was Latinised into "juria", meaning forest (i.e., "Jura" is forest mountains).[5][6][8] Divisions[edit] Key events in the Jurassic An approximate timescale of key Jurassic events. Various dinosaurs roamed forests of similarly large conifers during the Jurassic period. Paleogeography and tectonics[edit] During the early Jurassic period, the supercontinent Pangaea broke up into the northern supercontinent Laurasia and the southern supercontinent Gondwana; the Gulf of Mexico opened in the new rift between North America and what is now Mexico's Yucatan Peninsula.

Homininae Homininae is a subfamily of Hominidae that includes humans, gorillas, chimpanzees, bonobos and some extinct relatives; it comprises all hominids that arose after the split from orangutans (Ponginae). The Homininae cladogram has three main branches, which lead to gorillas, chimpanzees and bonobos, and humans. There are several extant species of chimpanzees and gorillas, but only one human species remains, although traces of several hypothetical species have been found with dates as recent as 12,000 years ago (Homo floresiensis, Homo denisova). History of discoveries and classification[edit] Today, chimpanzees and gorillas live in tropical forests with acid soils that rarely preserve fossils. Taxonomic classification[edit] Homininae[5][6] Evolution[edit] Evolution of bipedalism[edit] Recent studies of Ardipithecus ramidus (4.4 million years old) and Orrorin tugenensis (6 million years old) suggest some degree of bipedalism. Brain size evolution[edit] See also[edit] Notes[edit] Citations[edit]

One metre-tall human challenges history of evolution | Science Australian and Indonesian scientists have identified a new and completely unexpected species of human. It was only a metre high, had a small brain but a distinctly human face. It made delicate stone tools and it shared the planet with Homo sapiens at least 18,000 years ago. The scientists report in Nature today that they found the skull and incomplete skeleton of creature known as LB1 in the sediments of a limestone cave at Liang Bua on the remote island of Flores in Indonesia last September. Since then, fragments of bone from at least seven individuals have been found. The new creature, officially titled Homo floresiensis but nicknamed "the hobbit" by some researchers, upsets the orthodox view of human evolution. It means that researchers will now start looking for unexpected human remains in other isolated regions of the world. It also confirms the belief that modern humans - the only survivors of the genus Homo - are an evolutionary exception. "How did it live?

New human species found in Siberia | Science The remains of a little finger discovered in a cave in the mountains of southern Siberia belong to a previously unknown human ancestor, scientists said today. The finding suggests an undocumented human species lived alongside Neanderthals and early modern humans in parts of Asia as recently as 30,000 years ago. If confirmed, it would be the first time a new human ancestor has been identified since the discovery of Homo floresiensis, the diminutive "hobbits" that lived on the Indonesian island of Flores until 13,000 years ago. Fragments of the finger bone were recovered from Denisova cave in the Altai mountain range that straddles Russia, Mongolia, China and Kazakhstan. The cave was occupied by humans for 125,000 years and a variety of stone tools and bones have been recovered. The size of the bone has led scientists to believe it came from a child, aged between five and seven, though they are unable to say whether it was male or female.

Scientists discover hominid cranium in Ethiopia Last modified: Monday, March 27, 2006 FOR IMMEDIATE RELEASE March 27, 2006 BLOOMINGTON, Ind. -- A team of scientists conducting palaeoanthropological field research at Gona, in the Afar Administrative State of Ethiopia, have discovered a significantly complete cranium of a human ancestor estimated to be Middle Pleistocene in age. The new hominid was discovered at Gawis (pronounced "gow-wees"), in the Gona Paleoanthropological Research Project study area of Ethiopia. Scientists have reported finding a nearly complete cranium of a human ancestor estimated to be Middle Pleistocene in age. Print-Quality Photo The new cranium from Gawis appears to be intermediate between the earlier Homo erectus and later Homo sapiens and may be sampling a single lineage. The southwest portion of the project area near the Gawis River contains the youngest part of the archive, which is estimated to the Middle Pleistocene, a period from 780,000 to 125,000 years ago. Support Primary contact: Other contacts: