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Ordovician Mac OS

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Ordovician Mass Extinction Percent Of Life
Ordovician Mass Extinction Event

OrdovicianMac.zip 41 MB. OrdovicianPC.zip 40 MB. Log in with itch.io to leave a comment. JupiterHadley 5 years ago. Some freaky looking sea.
The user has requested enhancement of the downloaded file.Some of the authors of this publication are also working on these related projects: The Genesis of Moncorvo Iron Ore Deposit and The Use of Portable XRF and XRD for Grade Control (PhD thesis) View project Calymenina Trilobites from Devonian of Portugalfollowing this page was uploaded by Carlos Augusto Pinto Meireles on 09 December 2016.
GitHub - ordovician/PLists.jl: Reading and writing standard config files on macOS and NeXT. Just the plain text versions of the plist format.

The four eras of geological time

Automatic translation

Category: evolution
Updated June 01, 2013

There are 4.55 billion years, the dust of ancient giant stars are proto solar nebula rotated about what will become of our Sun.
The Earth is not constituted.
The disk surrounding the proto-sun heats up at birth, size reached 200 AU (astronomical unit). It begins to solidify and the atoms stick to each other to form grains of material. Thus sets up the accretion will lead to the formation of planets. Of dust grains condense, gravity increases attracting more and more objects, large and small. Over time a large ball covered with lava rock, is formed.

At this point resembles the young Earth, a huge ball molten rock.
Since the first microorganisms to man through the first oxygenated atmosphere, the first aerobic organisms, the first animals to external skeleton in the seas, the first fish, the first marine and terrestrial reptiles, the first plants, first insects, dinosaurs, mammals and primates, the Earth has left traces that have allowed us to define the characteristics eras in its history.
The Earth is only half of his life and the geological eras to come, remain very long.

Geological time span of today, there are 4.55 billion years, time of the birth of the Earth.
This story begins with the first geological eon of Earth, the Hadean through the Archean, Proterozoic, and the ends of the Phanerozoic. The Hadean is 700 million years, the Achaean my 1300, the Proterozoic and Phanerozoic 2000 my 540 my. Eras are best defined naturally on the last million years.

Image: The geological eons of Earth, the Hadean to now, the Phanerozoic.

Ordovician

The Ordovician is the second of six geological systems constituting the Paleozoic located himself in the last geological eon, the Phanerozoic. It takes 45 million years and extends from -488.3 ± 1.7 to -443.7 ± 1.5 million years.
The term Ordovician, from the name of the Celtic tribe of Ordovices, was created in the 19th century by Charles Lapworth to designate a stratigraphic sequence from north Wales.
During the Ordovician sea level reached a maximum, however, there is a supercontinent, Gondwana from the fracture of an even older supercontinent, Rodinia.
It is in the Ordovician that the diversity of marine life explodes with the so-called 'events of the Great Ordovician Biodiversification' (Great Ordovician Biodiversification Event: GOBE).

Life in the Ordovician

The first explosion of life date from the Cambrian (-542 to -488 million years) with the emergence of the main current animal living in the seabed. But it was in the Ordovician that the oceans are full of life with a truly exceptional increase in the number of marine organisms.
The study of reasons for this 'Great Ordovician Biodiversification' was the subject of an international program, the International Geoscience Program (IGCP) Project No. 503, Ordovician Palaeogeography and Palaeoclimate, in which several French teams participated.
The synthesis of these results, published in the journal GSA Today in 2010, explains that the key factor in the expansion of marine life in the Ordovician, was the increase in areas where the continental shelf seas are shallow and rich in life.

The Ordovician period is known as one of particular interest to life.
After the breakup of Rodinia, Precambrian supercontinent on the separation of continents has reached its maximum, before coming together again to form Pangaea, Permian, in the late Paleozoic.
The Ordovician period is the Paleozoic that had the largest number of continents.
Source: CNRS / INSU

Image: Limestone in trilobites, brachiopods, corals, gastropods (Lower Silurian), Anticosti Island, Quebec, Canada.
© Axel Munnecke, Universität Erlangen-Nürnberg

Mass extinction of the Ordovician

The Ordovician was a time of giving shallow inland sea rich in life, animal life existed only in the sea but there are about 440 to 445 million years, at the boundary between the Ordovician and Silurian two mass extinctions occur.
Although the geological eras are all marked by more or less massive extinctions, the five major extinctions in the Phanerozoic are known, including that of the transition between the Ordovician and Silurian.
During the Ordovician, nearly all the submerged lands were located south of the equator.
A period of glaciation would have resulted in climatic and ecological disturbances, it seems to be the cause of this extinction.
The diversity of marine life would have declined because of lower sea level restricting ecosystems.
Older brands streaks left by glaciers, indicating that a large Gondwana ice cap at the end of the Ordovician.
This ice age would have made it difficult for the adaptation of species and ecosystems with a decline of the sea hundreds of kilometers.
Like all great chapters in the history of the Earth, beginning with the Ordovician species that had survived several extinctions.
The mass extinction that would end the Ordovician, touched mainly trilobites, which became the most important arthropod of the time. Insects, scorpions, spiders and crustaceans belong to the phylum arthropods.
Extinction dates are only approximate because in ancient times, they are set by the fossil record, with dates in broad ranges, and refined over time by other scientific discoveries.

Image: Mass extinctions according Raupp, D.M. 1993.
L'extinctions des espèces. Gallimard.

Image: Biodiversity evolution in the Phanerozoic.
Mass extinctions have always been followed by explosions radiative (rapid evolution of species). Species disappearing free ecological niches for other species will benefit.

Conditions for the emergence of life...	The world population, always galloping...	The smallest frog in the world...	Kamchatka crab giant...	Neanderthal, the first man disappeared...	This animal is immortal...
Toumai our ancestor, old 7 million years...	Megapode uses the volcanic heat...	Ardi is older than 4 million years...	Life in the abyss is surprising...	Explosion of life in the Ordovician...	Natural selection, the peppered birch...
Liquid water, accelerator of chemical reactions...	Cosmic rays and mutation of species...	Bioluminescence of living organisms	The bipedalism in hominids...	Story of the evolution towards the living...	Primordial soup...

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The rocks that originated during the Ordovician Period constitute the Ordovician System. The Ordovician System is divided into seven stages—two each from the early and middle epochs and three from the late epoch. Of these, only three stages are named. A new species of echinoid, Bothriocidaris maquoketensis, has been discovered in the Cincinnatian (Upper Ordovician) Fort Atkinson Formation, Maquoketa Group, of northeastern Iowa. The new species is characterized by two widely spaced primary perforate tubercles on opposite sides of the peripodia and by numerous paired interambulacral plates.

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Mac Os Versions

The Ordovician environment
- Paleogeography
  - Oceanography
Ordovician life
- Marine organisms
- Terrestrial organisms
- Ordovician radiation
- Extinctions
Ordovician geology

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Join Britannica's Publishing Partner Program and our community of experts to gain a global audience for your work! Steven M. Holland

Professor of Geology, University of Georgia, Athens.

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 began. Ordovician rocks have the distinction of occurring at the highest elevation on Earth—the top of Mount Everest.

The Ordovician Period ushered in significant changes in plate tectonics, climate, and biological systems. Rapid seafloor spreading at oceanic ridges fostered some of the highest global sea levels in the Phanerozoic Eon. As a result, continents were flooded to an unprecedented level, with North America almost entirely underwater at times. These seas deposited widespread blankets of sediment that preserved the extraordinarily abundant fossil remains of marine animals. Numerical models of the Ordovician atmosphere estimate that levels of carbon dioxide were several times higher than today. This would have created warm climates from the Equator to the poles; however, extensive glaciation did occur for a brief time over much of the Southern Hemisphere at the end of the period.

The Ordovician Period was also characterized by the intense diversification (an increase in the number of species) of marine animal life in what became known as the Ordovician radiation. This event precipitated the appearance of almost every modern phylum (a group of organisms having the same body plan) of marine invertebrate by the end of the period, as well as the rise of fish. Ordovician seas were filled with a diverse assemblage of invertebrates, dominated by brachiopods (lamp shells), bryozoans (moss animals), trilobites, mollusks, echinoderms (a group of spiny-skinned marine invertebrates), and graptolites (small, colonial, planktonic animals). On land the first plants appeared, as well as possibly the first invasion of terrestrial arthropods. The end of the Ordovician was heralded by a mass extinction, the second largest in Earth’s history. (The largest mass extinction took place at the end of the Permian Period and resulted in the loss of about 90 percent of existing species; see alsoPermian extinction.)

The Ordovician was demarcated in the late 19th century as a compromise in a dispute over the boundaries of the Cambrian and Silurian systems. Studying the rock succession from northwest to southeast within Wales, English geologist Adam Sedgwick named the Cambrian System in 1835. At the same time and working in the opposite direction, Scottish geologist Roderick Murchison named the Silurian System. Both geologists expanded their systems until they overlapped, triggering a scientific feud. English geologist Charles Lapworth proposed the Ordovician System (named for an ancient Celtic tribe of northern Wales called the Ordovices) in 1879 to define the disputed overlapping interval. Lapworth’s proposal was resisted in Britain into the 1890s and, despite subsequent widespread international usage, was not officially adopted there until 1960.

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The Ordovician is divided into three epochs: Early Ordovician (485.4 million to 470 million years ago), Middle Ordovician (470 million to 458.4 million years ago), and Late Ordovician (458.4 million to 443.8 million years ago).

The Ordovician environment

Paleogeography

During the Ordovician Period, four major continents were present and separated by three major oceans. Although the positions of these continents are frequently updated with new evidence, current understanding of their position is based on paleomagnetic evidence, fossil markers, and climatically sensitive sediments, such as evaporite minerals. The craton (stable interior portion of a continent) of Laurentia—made up of most of present-day North America, Greenland, and part of Scotland—straddled the Equator and was rotated approximately 45° clockwise from its present orientation. The craton made up of Siberian and Kazakhstania (which is also called Siberia-Kazakhstan) lay east of Laurentia, along and slightly north of the Equator. The Iapetus Ocean separated these two landmasses on the south from the Baltica craton, which included present-day Scandinavia and north-central Europe. The microcontinent of Avalonia—made up of England, New England, and maritime Canada—was positioned to the west of Baltica and also faced Laurentia across the Iapetus Ocean. The Paleotethys Sea separated Avalonia, Baltica, and Kazakhstan from the supercontinent of Gondwana, which consisted of Africa, South America, India, Arabia, China, Australia, Antarctica, Western Europe, the southeastern United States, and the Yucatán Peninsula of Mexico. This immense supercontinent straddled both the South Pole, located then in what is now northwest Africa, and the Equator, which then crossed present-day Australia and Antarctica. In this position, Africa and South America were rotated nearly 180° from their present orientation. A single body of water, the Panthalassic Ocean, covered almost the entire Northern Hemisphere and was as wide at the Equator as the modern Pacific Ocean.

Ordovician Mass Extinction Percent Of Life

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Ordovician Mass Extinction Event

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