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The categorisation of the past into discrete, quantified named blocks of time is called periodization. [1] This is a list of such named time periods as defined in various fields of study. These can be divided broadly into prehistorical periods and historical periods (when written records began to be kept).
Diagram illustrating how the uterus lining builds up and breaks down during the menstrual cycle Menstruation (also known as a period, among other colloquial terms) is the regular discharge of blood and mucosal tissue from the inner lining of the uterus through the vagina. The menstrual cycle is characterized by the rise and fall of hormones. Menstruation is triggered by falling progesterone ...
See history, history by period, and periodization for different organizations of historical events. For earlier time periods, see Timeline of the Big Bang , Geologic time scale , Timeline of evolution , and Logarithmic timeline .
The Triassic (/ t r aɪ ˈ æ s ɪ k / try-ASS-ik; sometimes symbolized 🝈) [8] is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago (), to the beginning of the Jurassic Period 201.4 Mya. [9]
Menstruation (also called menstrual bleeding, menses or a period) is the first and most evident phase of the uterine cycle and first occurs at puberty. Called menarche, the first period occurs at the age of around twelve or thirteen years. [8] The average age is generally later in the developing world and earlier in the developed world. [42]
The Permian (/ ˈ p ɜːr m i. ə n / PUR-mee-ən) [4] is a geologic period and stratigraphic system which spans 47 million years from the end of the Carboniferous Period 298.9 million years ago (Mya), to the beginning of the Triassic Period 251.902 Mya. It is the sixth and last period of the Paleozoic Era; the following Triassic Period belongs ...
The name is derived from the Latin creta, 'chalk', which is abundant in the latter half of the period. It is usually abbreviated K, for its German translation Kreide. The Cretaceous was a period with a relatively warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas.
Azolla event may have ended a long warm period 5.3–2.6: Pliocene climate became cooler and drier, and seasonal, similar to modern climates. 2.5 to present: Quaternary glaciation, with permanent ice on the polar regions, many named stages in different parts of the world