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 determine the age of rocks). It is used primarily by Earth scientists (including geologists, paleontologists, geophysicists, geochemists, and paleoclimatologists) to describe the timing and relationships of events in geologic history. The time scale has been developed through the study of rock layers and the observation of their relationships and identifying features such as lithologies, paleomagnetic properties, and fossils. The definition of standardised international units of geological time is the responsibility of the International Commission on Stratigraphy (ICS), a constituent body of the International Union of Geological Sciences (IUGS), whose primary objective is to precisely define global chronostratigraphic units of the International Chronostratigraphic Chart (ICC) that are used to define divisions of geological time. The chronostratigraphic divisions are in turn used to define geochronologic units.
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👉 Geological epoch in the context of Catastrophism
In geology, catastrophism is the theory that the Earth has largely been shaped by sudden, short-lived, violent events, possibly worldwide in scope.This contrasts with uniformitarianism (sometimes called gradualism), according to which slow incremental changes, such as erosion, brought about all the Earth's geological features. The proponents of uniformitarianism held that the present was "the key to the past", and that all geological processes (such as erosion) throughout the past resembled those that can be observed today. Since the 19th-century disputes between catastrophists and uniformitarians, a more inclusive and integrated view of geologic events has developed, in which the scientific consensus accepts that some catastrophic events occurred in the geologic past, but regards these as extreme examples of explicable natural processes.
Proponents of catastrophism proposed that each geological epoch ended with violent and sudden natural catastrophes such as major floods and the rapid formation of major mountain chains. Plants and animals living in the parts of the world where such events occurred became extinct, to be replaced abruptly by the new forms whose fossils defined the geological strata. Some catastrophists attempted to relate at least one such change to the Biblical account of Noah's flood.
Geological epoch in the context of Anthropocene
Anthropocene is a term that has been used to refer to the period of time during which humanity has become a planetary force of change. It appears in scientific and social discourse, especially with respect to accelerating geophysical and biochemical changes that characterize the 20th and 21st centuries on Earth. Originally a proposal for a new geological epoch following the Holocene, it was rejected as such in 2024 by the International Commission on Stratigraphy (ICS) and the International Union of Geological Sciences (IUGS).
The term has been used in research relating to Earth's water, geology, geomorphology, landscape, limnology, hydrology, ecosystems and climate. The effects of human activities on Earth can be seen, for example, in regards to biodiversity loss, and climate change. Various start dates for the Anthropocene have been proposed, ranging from the beginning of the Neolithic Revolution (12,000–15,000 years ago), to as recently as the 1960s. The biologist Eugene F. Stoermer is credited with first coining and using the term anthropocene informally in the 1980s; Paul J. Crutzen re-invented and popularized the term.
Geological epoch in the context of British history
The history of the British Isles began with its sporadic human habitation during the Palaeolithic from around 900,000 years ago. The British Isles has been continually occupied since the early Holocene, the current geological epoch, which started around 11,700 years ago. Mesolithic hunter-gatherers migrated from the Continent soon afterwards at a time when there was no sea barrier between Britain and Europe, but there was between Britain and Ireland. There were almost complete population replacements by migrations from the Continent at the start of the Neolithic around 4,100 BC and the Bronze Age around 2,500 BC. Later migrations contributed to the political and cultural fabric of the islands and the transition from tribal societies to feudal ones at different times in different regions.
England and Scotland were sovereign kingdoms until 1603, and then legally separate under one monarch until 1707, when they united as one kingdom. Wales and Ireland were composed of several independent kingdoms with shifting boundaries until the medieval period.