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]
KIC 12557548 History of detection[edit] The existence of the planet was first evidenced in data collected by the Kepler spacecraft. However, the light curve of the star, a graph of its stellar flux versus time, showed that while there were regular drops in stellar flux approximately every 15 hours, the amount of light being blocked covered a wide range, from 0.2% to 1.3% of the starlight being blocked.[2] Rappaport et al. (2012) proposed various possible phenomena which may have caused the anomalies in the light curve, including two planets orbiting each other,[6] and an eclipsing binary orbiting the star in a larger triple-star system.[2] However, the authors found the hypothetical binary planet system to be unstable[2] and the latter scenario to be poorly supported by the data collected by Kepler.[2] Planetary system[edit] References[edit] ^ Jump up to: a b c d e f "Basic data: 2MASS J19235189+5130170 -- Infra-Red source". Brogi, M.; Keller, C. Notes[edit] External links[edit]
untitled Geologic time scale Online exhibits Geologic time scale Take a journey back through the history of the Earth — jump to a specific time period using the time scale below and examine ancient life, climates, and geography. You might wish to start in the Cenozoic Era (65.5 million years ago to the present) and work back through time, or start with Hadean time (4.6 to 4 billion years ago)* and journey forward to the present day — it's your choice. Ways to begin your exploration: Use the links in the "time machine" below and explore a specific period that interests you.Read more about the geologic time scale, its origins and its time divisions.Find out more about plate tectonics, an important geological concept in any time period!
Future of the Earth Conjectured illustration of the scorched Earth after the Sun has entered the red giant phase, 7 billion years from now.[1] During the next four billion years, the luminosity of the Sun will steadily increase, resulting in a rise in the solar radiation reaching the Earth. This will cause a higher rate of weathering of silicate minerals, which will cause a decrease in the level of carbon dioxide in the atmosphere. In about 600 million years, the level of CO 2 will fall below the level needed to sustain C3 carbon fixation photosynthesis used by trees. Some plants use the C4 carbon fixation method, allowing them to persist at CO 2 concentrations as low as 10 parts per million. In about 1.1 billion years, the solar luminosity will be 10% higher than at present. Human influence[edit] There are multiple scenarios for known risks that can have a global impact on the planet. Should the human race become extinct, then the various features assembled by humanity will begin to decay. Glaciation[edit]
untitled Prehistory Prehistory (meaning "before history", or "before knowledge acquired by investigation", from the Latin word for "before," præ, and historia) is the span of time before recorded history or the invention of writing systems. Prehistory refers to the period of human existence before the availability of those written records with which recorded history begins.[1] More broadly, it can refer to all the time preceding human existence and the invention of writing. The notion of "prehistory" began to surface during the Enlightenment in the work of antiquarians who used the word 'primitive' to describe societies that existed before written records.[2] The first use of the word prehistory in English, however, occurred in the Foreign Quarterly Review in 1836.[3] The occurrence of written materials (and so the beginning of local "historic times") varies generally to cultures classified within either the late Bronze Age or within the Iron Age. Definition[edit] Stone Age[edit] Paleolithic[edit] uninhabited
Holocene extinction The dodo, a flightless bird of Mauritius, became extinct during the mid-late seventeenth century after humans destroyed the forests where the birds made their homes and introduced mammals that ate their eggs. The Holocene extinction includes the disappearance of large mammals known as megafauna, starting between 9,000 and 13,000 years ago, the end of the last Ice Age. This may have been due to the extinction of the mammoth that had maintained grasslands that became birch forests without the mammoths.[3] The new forest and the resulting forest fires may have induced climate change.[3] Such disappearances might be the result of the proliferation of modern humans which led to climate change. These extinctions, occurring near the Pleistocene–Holocene boundary, are sometimes referred to as the Quaternary extinction event. The Holocene extinction continues into the 21st century. Prehistoric extinctions[edit] North and South America[edit] New Zealand[edit] Pacific, including Hawaii[edit]
untitled Geology Entrance You might wish to start in the Cenozoic Era (65 million years ago to the present) and work back through time, or start with Hadean time (4.5 to 3.8 billion years ago) and journey forward to the present day. No matter "when" you start, don't forget to stop along the way to learn about the stratigraphy, ancient life, fossil localities, and tectonics of the various time periods. Here are three links that can help to speed your journey: 1) Get helpful hints on navigating the Geology Wing. 2) Read about the history of the geologic time scale, and find out more about how it is organized. 3) Jump to a specific time period using the UCMP Geological Time Machine. Last but not least, don't forget to visit our exhibit on Plate tectonics, an important geological concept in any time period!
Ross 248 This star has about 12% of the Sun's mass and 16% of the Sun's radius, but only 0.2% of the Sun's luminosity. It has a stellar classification of M6 V,[3] which indicates it is a type of main sequence star known as a red dwarf. This is a flare star that occasionally increases in luminosity.[13] With high probability there appears to be a long-term cycle of variability with a period of 4.2 years. Long term observations of this star by the Sproul Observatory show no astrometric perturbations by an unseen companion.[15] The proper motion of this star was examined for a brown dwarf or stellar companion orbiting at a wide separation (between 100–1400 AU) but none was found.[16] A search for a faint companion using the Hubble Space Telescope Wide Field Planetary Camera revealed nothing,[7] nor did a search with near-infrared speckle interferometry.[17] However, none of these searches rule out a companion that is smaller than the detection minima. Field star[edit] See also[edit] References[edit]
untitled 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
Tidal acceleration A picture of the Earth and the Moon from Mars. The presence of the moon (which has about 1/81 the mass of Earth), is slowing Earth's rotation and lengthening the day by about 2 ms every century. Tidal acceleration is an effect of the tidal forces between an orbiting natural satellite (e.g. the Moon), and the primary planet that it orbits (e.g. Earth). The similar process of tidal deceleration occurs for satellites that have an orbital period that is shorter than the primary's rotational period, or that orbit in a retrograde direction. The naming is somewhat confusing, because the actual speed of the satellite is decreased as a result of tidal acceleration, and increased as a result of tidal deceleration. Earth–Moon system[edit] Discovery history of the secular acceleration[edit] Edmond Halley was the first to suggest, in 1695,[1] that the mean motion of the Moon was apparently getting faster, by comparison with ancient eclipse observations, but he gave no data. Historical evidence[edit]