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Million years ago, abbreviated as Mya, Myr (megayear) or Ma (megaannum), is a unit of time equal to 1,000,000 years (i.e. 1 × 10 6 years), or approximately 31.6 teraseconds. Usage [ edit ]
A megaannus (Ma) represents one million (10 6) years. The geologic time scale or geological time scale ( GTS ) is a representation of time based on the rock record of Earth . It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochronology (a scientific branch of geology that aims to ...
The Proterozoic eon lasted from 2.5 Ga to 538.8 Ma (million years) ago. [105] In this time span, cratons grew into continents with modern sizes. The change to an oxygen-rich atmosphere was a crucial development. Life developed from prokaryotes into eukaryotes and multicellular forms.
1.1 13,800 million years ago to 5,500 million years ago. ... (359–299 Ma), beginning of Permian period (299–252 Ma) First large sharks, ratfish and hagfish.
The Ca-Al-rich inclusions, which formed 2 million years before the chondrules, [1] are a key signature of a supernova explosion. c. 4,567 ±3 Ma – Rapid collapse of hydrogen molecular cloud , forming a third-generation Population I star , the Sun , in a region of the Galactic Habitable Zone (GHZ), about 25,000 light years from the center of ...
The Late Ordovician mass extinction (LOME), sometimes known as the end-Ordovician mass extinction or the Ordovician-Silurian extinction, is the first of the "big five" major mass extinction events in Earth's history, occurring roughly 445 million years ago (Ma). [1]
The Cretaceous (IPA: / k r ɪ ˈ t eɪ ʃ ə s / krih-TAY-shəss) [2] is a geological period that lasted from about 143.1 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 77 million years, it is the ninth and longest geological period of the entire Phanerozoic.
The Cambrian (/ ˈ k æ m b r i. ə n, ˈ k eɪ m-/ KAM-bree-ən, KAYM-) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. [5] The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordovician Period 486.85 Ma.