Geologic Time Periods Time Scale Facts Britannica

Geologic Time Periods Time Scale Facts Britannica The geologic time scale is the “calendar” for events in earth history. it subdivides all time into named units of abstract time called—in descending order of duration— eons, eras, periods, epochs, and ages. the enumeration of those geologic time units is based on stratigraphy, which is the correlation and classification of rock strata. Geologists have mapped out a time scale that is a “calendar” of earth’s geologic history. the scale of geologic time starts some 4 billion years ago, when earth’s crust was formed. earth itself is slightly older than this, but when it was first formed the planet was in a hot and thick liquid form. as it cooled, the surface of the planet.

Geologic Time Periods Time Scale Facts Britannica The quaternary period (2.6 million years ago to the present) is composed of the pleistocene and holocene epochs. the holocene epoch began 11,700 years ago and continues into modern time. the vast interval of time that spans earth’s geologic history is known as geologic time. it began roughly 4.6 billion years ago when earth began to form as a. The pregeologic period. from the point at which the planet first began to form, the history of earth spans approximately 4.6 billion years. the oldest known rocks—the faux amphibolites of the nuvvuagittuq greenstone belt in quebec, canada—however, have an isotopic age of 4.28 billion years. there is in effect a stretch of approximately 300. The geologic time scale is a chart containing the names and time ranges of the eons, eras, periods, and other divisions of geologic time. the scale extends from the archean eon more than 3.6 billion years ago (bottom right) to the quaternary period of the present day (upper left). Geologic time scale showing the geologic eons, eras, periods, epochs, and associated dates in millions of years ago (mya). the time scale also shows the onset of major evolutionary and tectonic events affecting the north american continent and the northern cordillera (scak, south central alaska; seak, southeast alaska; nak, northern alaska; cak central alaska).