An epoch is the second smallest geochronologic unit. It is equivalent to a chronostratigraphic series. [14] [13] There are 37 defined epochs and one informal one. The current epoch is the Holocene. There are also 11 subepochs which are all within the Neogene and Quaternary. [2]

Jan 17, 2025 · 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.

Each eon saw the most significant changes in Earth's composition, climate and life. Each eon is subsequently divided into eras, which in turn are divided into periods, which are further divided into epochs. Earth is formed out of debris around the solar protoplanetary disk. There is no life.

The geological history of Earth follows the major geological events in Earth's past based on the geologic time scale, a system of chronological measurement based on the study of the planet's rock layers (stratigraphy).

The Geologic Time Scale is divided into four eons, ten eras, 22 periods, and several epochs and ages. Each eon, era, period, and epoch is defined by major geological or paleontological events. The eons are the Hadean, Archean, Proterozoic, and Phanerozoic.

Oct 5, 2021 · 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 ...

Jan 11, 2025 · The Geologic Time Scale or Geological Time Scale (GTS) is a chronological framework that organizes Earth’s history into various units based on geological and paleontological evidence. It divides Earth’s 4.6 billion-year history into hierarchical units such as eons, eras, periods, epochs, and ages.

Feb 28, 2020 · Geologic time spans are divided into units and subunits, the largest of which are eons. Eons are divided into eras, which are further divided into periods, epochs, and ages. Geologic dating is extremely imprecise.

In the Silurian Period, Britain lay south of the equator with a tropical to subtropical climate. A sea covered Britain that was shallower in the south (limestones) and deeper in the north (sandstones and mudstones).

Because of its usefulness for communicating about events in Earth's history, it is important that all students of geology, paleontology, and evolutionary biology commit the geological time scale to memory. This is most easily done by first breaking the time scale into its component parts: eons, eras, periods, and epochs.