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dating

(Encyclopedia)dating, the determination of the age of an object, of a natural phenomenon, or of a series of events. There are two basic types of dating methods, relative and absolute. In relative dating, the tempor...

Anthropocene

(Encyclopedia)Anthropocene Epoch, an unofficial term used by scientists to describe a period of time—up to the present—in which humanity has impacted the planet on a global scale. The phrase was fir...

Jurassic period

(Encyclopedia)Jurassic period jərăsˈĭk [key] [from the Jura Mts.], second period of the Mesozoic era of geologic time, lasting from 213 to 144 million years ago. At the start of the Jurassic most of the contine...

coal

(Encyclopedia)coal, fuel substance of plant origin, largely or almost entirely composed of carbon with varying amounts of mineral matter. Coal is found in beds or seams interstratified with shales, clays, sands...

Permian period

(Encyclopedia)Permian period pûrˈmēən [key] [from Perm, Russia], sixth and last period of the Paleozoic era (see Geologic Timescale, tablegeologic timescale, table) from 250 to 290 million years ago. Many ma...

plant

(Encyclopedia)plant, any organism of the plant kingdom, as opposed to one of the animal kingdom or of the kingdoms Fungi, Protista, or Monera in the five-kingdom system of classification. (A more recent system, sug...

air pollution

(Encyclopedia)air pollution, contamination of the air by noxious gases and minute particles of solid and liquid matter (particulates) in concentrations that endanger health. The major sources of air pollution are t...

power, electric

(Encyclopedia)power, electric, energy dissipated in an electrical or electronic circuit or device per unit of time. The electrical energy supplied by a current to an appliance enables it to do work or provide some ...

Australopithecus

(Encyclopedia)Australopithecus ôstrāˌlōpĭthˈəkəs, –pəthēˈkəs [key], an extinct hominin genus found in Africa between about 4 and 1 million years ago. At least seven species of australopithecines are n...

mass extinction

(Encyclopedia)mass extinction, the extinction of a large percentage of the earth's species, opening ecological niches for other species to fill. There have been at least ten such events. The five greatest were thos...