Chronological dating in the context of "Geologic epoch"

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). Earth formed approximately 4.54 billion years ago through accretion from the solar nebula, a disk-shaped mass of dust and gas remaining from the formation of the Sun, which also formed the rest of the Solar System.

Initially, Earth was molten due to extreme volcanism and frequent collisions with other bodies. Eventually, the outer layer of the planet cooled to form a solid crust when water began accumulating in the atmosphere. The Moon formed soon afterwards, possibly as a result of the impact of a protoplanet with Earth. Outgassing and volcanic activity produced the primordial atmosphere. Condensing water vapor, augmented by ice delivered from asteroids, produced the oceans. However, in 2020, researchers reported that sufficient water to fill the oceans may have always been on Earth since the beginning of the planet's formation.

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.

Germanic paganism or Germanic religion was the traditional, culturally significant religion of the Germanic peoples. With a chronological range of at least one thousand years in an area covering Scandinavia, the British Isles, modern Germany, the Netherlands, and at times other parts of Europe, the beliefs and practices of Germanic paganism varied. Scholars typically assume some degree of continuity between the beliefs and practices of the Roman era and those found in Norse paganism, as well as between Germanic religion and reconstructed Indo-European religion and post-conversion folklore, though the precise degree and details of this continuity are subjects of debate. Germanic religion was influenced by neighboring cultures, including that of the Celts, the Romans, and, later, by Christianity. Very few sources exist that were written by pagan adherents themselves; instead, most were written by outsiders and can thus present problems for reconstructing authentic Germanic beliefs and practices.

Some basic aspects of Germanic belief can be reconstructed, including the existence of one or more origin myths, the existence of a myth of the end of the world, a general belief in the inhabited world being a "middle-earth", as well as some aspects of belief in fate and the afterlife. The Germanic peoples believed in a multitude of gods, and in other supernatural beings such as jötnar (often glossed as giants), dwarfs, elves, and dragons. Roman-era sources, using Roman names, mention several important male gods, as well as several goddesses such as Nerthus and the matronae. Early medieval sources identify a pantheon consisting of the gods *Wodanaz (Odin), *Thunraz (Thor), *Tiwaz (Tyr), and *Frijjō (Frigg), as well as numerous other gods, many of whom are only attested from Norse sources (see Proto-Germanic folklore).

Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method for determining the age of an object containing organic material by using the properties of radiocarbon, a radioactive isotope of carbon.

The method was developed in the late 1940s at the University of Chicago by Willard Libby. It is based on the fact that radiocarbon (
C) is constantly being created in the Earth's atmosphere by the interaction of cosmic rays with atmospheric nitrogen. The resulting
C combines with atmospheric oxygen to form radioactive carbon dioxide, which is incorporated into plants by photosynthesis; animals then acquire
C by eating the plants. When the animal or plant dies, it stops exchanging carbon with its environment, and thereafter the amount of
C it contains begins to decrease as the
C undergoes radioactive decay. Measuring the amount of
C in a sample from a dead plant or animal, such as a piece of wood or a fragment of bone, provides information that can be used to calculate when the animal or plant died. The older a sample is, the less
C there is to be detected. The half-life of
C (the period of time after which half of a given sample will have decayed) is about 5,730 years, so the oldest dates that can be reliably measured by this process date to approximately 50,000 years ago, although special preparation methods occasionally make an accurate analysis of older samples possible. Libby received the Nobel Prize in Chemistry for his work in 1960.

Relative dating is the science of determining the relative order of past events (i.e., the age of an object in comparison to another), without necessarily determining their absolute age (i.e., estimated age). In geology, rock or superficial deposits, fossils and lithologies can be used to correlate one stratigraphic column with another. Prior to the discovery of radiometric dating in the early 20th century, which provided a means of absolute dating, archaeologists and geologists used relative dating to determine ages of materials. Though relative dating can only determine the sequential order in which a series of events occurred, not when they occurred, it remains a useful technique. Relative dating by biostratigraphy is the preferred method in paleontology and is, in some respects, more accurate. The Law of Superposition, which states that older layers will be deeper in a site than more recent layers, was the summary outcome of 'relative dating' as observed in geology from the 17th century to the early 20th century.

Geochronology is the science of determining the age of rocks, fossils, and sediments using signatures inherent in the rocks themselves. Absolute geochronology can be accomplished through radioactive isotopes, whereas relative geochronology is provided by tools such as paleomagnetism and stable isotope ratios. By combining multiple geochronological (and biostratigraphic) indicators the precision of the recovered age can be improved.

Geochronology is different in application from biostratigraphy, which is the science of assigning sedimentary rocks to a known geological period via describing, cataloging and comparing fossil floral and faunal assemblages. Biostratigraphy does not directly provide an absolute age determination of a rock, but merely places it within an interval of time at which that fossil assemblage is known to have coexisted. Both disciplines work together hand in hand, however, to the point where they share the same system of naming strata (rock layers) and the time spans utilized to classify sublayers within a stratum.