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It is commonly used as a unit of time to denote length of time before the present in 10 9 years. This initialism is often used in the sciences of astronomy , geology , and paleontology . The "billion" in bya is the 10 9 "billion" of the short scale of the U.S. , [ 1 ] not the long-scale 10 12 "billion" of some European usage.
Researchers at McGill University found a rock with a very old model age for extraction from the mantle (3.8 to 4.28 billion years ago) in the Nuvvuagittuq greenstone belt on the coast of Hudson Bay, in northern Quebec; [2] the true age of these samples is still under debate, and they may actually be closer to 3.8 billion years old. [3]
Although the term aeon may be used in reference to a period of a billion years (especially in geology, cosmology and astronomy), its more common usage is for any long, indefinite period. Aeon can also refer to the four aeons on the geologic time scale that make up the Earth's history, the Hadean , Archean , Proterozoic , and the current aeon ...
The Paleozoic (/ ˌ p æ l i. ə ˈ z oʊ. ɪ k,-i. oʊ-, ˌ p eɪ-/ PAL-ee-ə-ZOH-ik, -ee-oh-, PAY-; [1] or Palaeozoic) Era is the first of three geological eras of the Phanerozoic Eon. . Beginning 538.8 million years ago (Ma), it succeeds the Neoproterozoic (the last era of the Proterozoic Eon) and ends 251.9 Ma at the start of the Mesozoic Er
According to evidence from radiometric dating and other sources, Earth formed about 4.54 billion years ago. [7] [8] [9] The current dominant theory of planet formation suggests that planets such as Earth form in about 50 to 100 million years but more recently proposed alternative processes and timescales have stimulated ongoing debate in the planetary science community. [10]
The Mesozoic Era [3] is the era of Earth's geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Periods.It is characterized by the dominance of gymnosperms such as cycads, ginkgoaceae and araucarian conifers, and of archosaurian reptiles such as the dinosaurs; a hot greenhouse climate; and the tectonic break-up of Pangaea.
The geology of Australia includes virtually all known rock types, spanning a geological time period of over 3.8 billion years, including some of the oldest rocks on earth. Australia is a continent situated on the Indo-Australian Plate .
Estimates have placed the structure’s age to be 2.023 billion years (± 4 million years) [5] or 2.019/2.020 billion years (± 2-3 million years) old, [6] which places it in the Orosirian Period of the Paleoproterozoic Era. It is the second oldest universally accepted impact structure on Earth.