Before Present

Before Present (BP) years is a time scale used mainly in archaeology, geology and other scientific disciplines to specify when events occurred in the past. Because the "present" time changes, standard practice is to use 1 January 1950 as the commencement date of the age scale, reflecting the origin of practical radiocarbon dating in the 1950s. The abbreviation "BP" has alternatively been interpreted as "Before Physics";[1] that is, before nuclear weapons testing artificially altered the proportion of the carbon isotopes in the atmosphere, making dating after that time likely to be unreliable.[2][3]

In a convention that is not always observed, many sources restrict the use of BP dates to those produced with radiocarbon dating.

Usage of "BP"

The BP scale is sometimes used for dates established by means other than radiocarbon dating, such as stratigraphy.[4][5] This usage differs with the recommendation by van der Plicht & Hogg,[6] followed by the Quaternary Science Reviews,[7][8] both of which requested that publications should use the unit "a" for year and reserve the term "BP" for radiocarbon estimations.

Some archaeologists use the lowercase letters bp, bc and ad as terminology for uncalibrated dates for these eras.[9]

The Centre for Ice and Climate at the University of Copenhagen has proposed "b2k" as "years before AD 2000", based on the Greenland Ice Core Chronology 2005 (GICC05) time scale.[10]

Radiocarbon dating

Radiocarbon dating was first used in 1940. Beginning in 1954, metrologists established 1950 as the origin year for the BP scale for use with radiocarbon dating, using a 1950-based reference sample of oxalic acid. According to scientist A. Currie Lloyd:

The problem was tackled by the international radiocarbon community in the late 1950s, in cooperation with the U.S. National Bureau of Standards. A large quantity of contemporary oxalic acid dihydrate was prepared as NBS Standard Reference Material (SRM) 4990B. Its 14C concentration was about 5% above what was believed to be the natural level, so the standard for radiocarbon dating was defined as 0.95 times the 14C concentration of this material, adjusted to a 13C reference value of −19 per mil (PDB). This value is defined as "modern carbon" referenced to AD 1950. Radiocarbon measurements are compared to this modern carbon value, and expressed as "fraction of modern" (fM). "Radiocarbon ages" are calculated from fM using the exponential decay relation and the "Libby half-life" 5568 a. The ages are expressed in years before present (BP) where "present" is defined as AD 1950.[11]

The year 1950 was chosen because it was the standard astronomical epoch at that time. It also marked[2] the publication of the first radiocarbon dates in December 1949,[12] and 1950 also antedates large scale atmospheric testing of nuclear weapons, which altered the global ratio of carbon-14 to carbon-12.[13]

Radiocarbon calibration

Dates determined using radiocarbon dating come in two kinds: uncalibrated (also called Libby or raw) and calibrated (also called Cambridge) dates.[14] Uncalibrated radiocarbon dates should be clearly noted as such by "uncalibrated years BP", because they are not identical to calendar dates. This has to do with the fact that the level of atmospheric radiocarbon (carbon-14 or 14C) has not been strictly constant during the span of time that can be radiocarbon-dated. Uncalibrated radiocarbon ages can be converted to calendar dates by means of calibration curves based on comparison of raw radiocarbon dates of samples independently dated by other methods, such as dendrochronology (dating on the basis of tree growth-rings) and stratigraphy (dating on the basis of sediment layers in mud or sedimentary rock). Such calibrated dates are expressed as cal BP, where "cal" indicates "calibrated years", or "calendar years", before 1950.

Many scholarly/scientific journals require that published calibrated results be accompanied by the name (standard codes are used) of the laboratory concerned, and other information such as confidence levels, because of differences between the methods used by different laboratories and changes in calibrating methods.

Other dating conventions

See also


  1. ^ Flint, Richard Foster; Deevey, Edward S (1962). "Volume 4 – 1962". Radiocarbon. 4 (1): i.
  2. ^ a b Taylor RE (1985). "The beginnings of radiocarbon dating in American Antiquity: a historical perspective". American Antiquity. 50 (2): 309–325. doi:10.2307/280489.
  3. ^ Dincauze, Dena (2000). "Measuring time with isotopes and magnetism". Environmental Archaeology: Principles and Practice. Cambridge, England: Cambridge University Press. p. 110. ISBN 978-0-5213-1077-2.
  4. ^ "AGU Editorial Style Guide for Authors". American Geophysical Union. 21 September 2007. Archived from the original on 2008-07-14. Retrieved 2009-01-09.
  5. ^ North American Commission on Stratigraphic Nomenclature (November 2005). "North American Stratigraphic Code: Article 13 (c)". The American Association of Petroleum Geologists Bulletin. 89 (11): 1547–1591. doi:10.1306/07050504129.
  6. ^ J. van der Plicht, A. Hogg (2006). "A note on reporting radiocarbon". Quaternary Geochronology. 1 (4): 237–240. doi:10.1016/j.quageo.2006.07.001.
  7. ^ "The use of time units in Quaternary Science Reviews". Quaternary Science Reviews. 26 (9–10): 1193. May 2007. Bibcode:2007QSRv...26.1193.. doi:10.1016/j.quascirev.2007.04.002.
  8. ^ Wolff, Eric W. (December 2007). "When is the "present"?". Quaternary Science Reviews. 26 (25–28): 3023–3024. Bibcode:2007QSRv...26.3023W. doi:10.1016/j.quascirev.2007.10.008.
  9. ^ Edward J. Huth (25 November 1994). Scientific Style and Format: The CBE Manual for Authors, Editors, and Publishers. Cambridge University Press. pp. 495–. ISBN 978-0-521-47154-1. Retrieved 4 October 2012.
  10. ^ "The GICC05 time scale". Centre for Ice and Climate - University of Copenhagen. Retrieved September 17, 2018.
  11. ^ Currie Lloyd A (2004). "The Remarkable Metrological History of Radiocarbon Dating [II]" (PDF). Journal of Research of the National Institute of Standards and Technology. 109: 185–217. doi:10.6028/jres.109.013.
  12. ^ Arnold JR, Libby WF (1949-03-04). "Age determinations by radiocarbon content: Checks with samples of known age". Science. 109 (2827): 227–228. Bibcode:1949Sci...109..227L. doi:10.1126/science.109.2827.227. PMID 17818054.
  13. ^ AD or BC? from
  14. ^ Greene, Kevin (2002). Archaeology: An Introduction. Philadelphia: University of Pennsylvania Press. pp. 165–167. ISBN 0-8122-1828-0.
Aguilera (volcano)

Aguilera (e. 2546 m/8353 ft.) is a stratovolcano in southern Chile, which rises above the edge of the Southern Patagonian Ice Field. It is a remote volcano that was identified as such in 1985, but the first ascent only occurred in 2014, making it the last unclimbed major Andean volcano.

It is located west of Lake Argentino and northeast of Peel Fjord in the southern Andes and erupted mainly dacites and pyroclastic tephra. It has erupted several times in the Holocene, with a major eruption taking place 3,000 ± 1,000 years before present. Its eruptions have spread ashfalls over Patagonia.


Ampato (possibly from Quechua hamp'atu or from Aymara jamp'atu, both meaning "frog") is a dormant 6,288-metre (20,630 ft) stratovolcano in the Andes of southern Peru. It lies about 70–75 kilometres (43–47 mi) northwest of Arequipa and is part of a north-south chain that includes the volcanoes Hualca Hualca and Sabancaya, the last of which has been active in historical time.

Ampato consists of three volcanic cones, which lie on top of an older eroded volcanic edifice. They were formed sequentially by extrusion of lava flows, but Ampato has also had explosive eruptions which have deposited ash, lapilli and pumice in the surrounding landscape. One young lava flow has been dated to 17,000 ± 6,000 years before present, but a summit lava dome is even younger, and Holocene ash layers in surrounding peat bogs may testify to the occurrence of recent eruptions.

The present-day volcano is covered by an ice cap, and during the last glacial maximum glaciers advanced to low altitudes. In 1995, an Inca mummy known as Mummy Juanita was discovered on Ampato by Johan Reinhard; it had been offered as a human sacrifice more than six hundred years earlier on the mountain.

Billion years

A billion years (109 years) is a unit of time on the petasecond scale, more precisely equal to 3.16×1016 seconds.

It is sometimes abbreviated Gy, Ga ("giga-annum"), Byr and variants. The abbreviations Gya or bya are for "billion years ago", i.e. billion years before present.

The terms are used in geology, paleontology, geophysics, astronomy and physical cosmology.

The prefix giga- is preferred over billion- to avoid confusion in the long and short scales over the meaning of billion; the postfix annum may be further qualified for precision as a sidereal year or Julian year:

1 Gaj=3.15576×1016 s,

1 Gas=3.15581×1016 s (epoch J2000.0).

1 Gas=1×109 yByr was formerly used in English-language geology and astronomy as a unit of one billion years. Subsequently, the term gigaannum (Ga) has increased in usage, with Gy or Gyr still sometimes used in English-language works (at the risk of confusion with Gy as abbreviation for the gray, a unit of radiation exposure). Astronomers use Gyr or Gy as an abbreviation for gigayear.

Bird stone

Bird stones are prehistoric, abstract stone carvings made by Native Americans. The artifacts were a common inclusion in graves and thought to have ceremonial importance. They are noted for their distinctive simplicity and beauty. They first appeared in the middle Archaic period around 5,000 years ago and continued into the early Woodland period to about 2,500 years before present.The exact purpose of these artifacts is not known, but most have a small hole drilled at the base of the neck and another at the aft end, presumably for mounting. Some theories suggest they were part of an atlatl (a short rod to hurl spears), in addition to their ceremonial uses. It has also been suggested that these artifacts were worn as decorative items denoting marriage status or pregnancy, and as totems representing tribes.Bird stones were mostly made east of the Mississippi, and the thousands in existence have been found primarily in New York, Ohio, Michigan and Wisconsin. The stones range in length from 3 to 6 inches, and have unique variations in style. Most are ground from grayish green, banded slate, and occasionally porphyry.

Bluefish Caves

Bluefish Caves is an archaeological site in Yukon, Canada, located 54 km (34 mi) southwest of the Vuntut Gwichin community of Old Crow, from which a specimen of allegedly human-worked mammoth bone has been radiocarbon dated to 24,000 years before present (BP), earlier than the generally accepted age for habitation of the New World.

Buena Vista, Peru

Buena Vista is an 8 hectare (20 acre) archaeological site located in Peru about 25 miles inland in the Chillon River Valley and an hour's drive north of Lima, the capital. It is in the Santa Rosa de Quives District, Canta Province, in the foothills of the Andes. The site was first excavated by Frederic Engel (1987). He obtained radiocarbon dates of artifacts that pertained to the Early Preceramic Period (9700 ± 200 uncalibrated radiocarbon years before present), and to the Early Intermediate Period (1960 ± 80 uncalibrated radiocarbon years before present).

In June 2004, archaeologist Robert Benfer and his team discovered Buena Vista’s most significant feature—the Temple of the Fox. It is named for the mural flanking the temple entrance, which depicts a fox curled up inside a llama. The Temple of the Fox dates back approximately 4200 years to a civilization that occupied the area a few millennia before the Inca. These ancient peoples had no writing system, and their name was not preserved; they are considered a late pre-ceramic culture and are believed to have followed the Kotosh religious tradition. Many archaeologists refer to them as the Andeans.The temple complex measures 33 feet tall and 55 feet long. It is most notable for the astronomical observatory at its top, which is the oldest of its kind in the Americas; it predates records of similar artistic and scientific achievements of the region by 800 years. Large rocks placed on a ridge to the east of the observatory entrance served as a calendar. The most prominent rock marked the summer solstice—on that day each year, from the perspective of the temple, the sun would rise directly over the rock. In the hours just before dawn on the summer solstice, a constellation known as the fox rose between two other large rocks on the same ridge.The temple’s reverence to the fox, apparent in both the entrance mural and its astrological orientation, may provide clues to the purpose of the temple. Among many indigenous peoples of South America, the fox is a symbol of water and cultivation. Benfer hypothesizes that the ancient inhabitants of Buena Vista used the Temple of the Fox to appeal to their gods for good harvests on the summer solstice, which would have been planting time for the civilization. Researchers' discovery of the remains of plants and vegetables inside the temple’s offering chamber has supported this theory.The observatory is further distinguished by its sophisticated carvings, and a three-dimensional life-size sculpture of a musician, unique for a period known in that region for two-dimensional reliefs.The Buena Vista site as a whole includes ruins ranging in age from 10,000 years to fewer than 3,000 years ago. Besides the temple, the site encompasses a ceremonial center, stepped pyramids, and residences for the elites and for commoners. These buildings are from varying time periods, many of which were built later than the heyday of the temple. Most of these structures have been looted. The Temple of the Fox narrowly escaped looting as it was buried beneath several layers of earth.


Bukkehåmmårtjørna is a small lake in eastern Jotunheimen. This is the highest lake that

has been investigated as a climate archive in southern Norway, being situated 1594 m above sea level.

A small glacier, Bukkehåmmårbreen, is draining meltwater into the lake at present. This glacier reformed just short of 6,000 years ago following the Holocene climate optimum and has existed continuously since. After growing gradually towards 4,000 years before present (BP) the glacier has been of near present size over the last 4,000 years, growing slightly larger over the last 2-2,500 years.

Prior to the climate optimum and following the deglaciation the glacier melted some 10,000 years before present.

The flat valley-shoulder that the lake is eroded into is locally known as a "fly". This particular level at about 1600 m a.s.l. and is believed to have been formed between 100 and 85 million years ago during the Cretaceous period. Standing on the shore-line of Bukkehåmmårtjørna thus means that you are standing on the remnants of a landscape that the Dinosaurs ruled.

The small lake existed prior to the Last Glacial Maximum since it contains organic material older than 30,000 years old. Currently being reassessed, growing evidence now indicates that much of the landscape that can be seen from this site is practically unchanged since the age of the Mammoth who lived on the wide plateaus more than 40,000 years ago.

The view from the lake, or higher up on the mountain-peak Høgdebrotet therefore includes a view into the landscapes of the distant past, including the landscape of the dinosaurs, the pre-ice age landscape, the landscape of the Mammoth during the last glacial period. By squinting your eyes and imagining the present forest-limit below, located some 300 m higher than at present and by imagining the glaciers of Leirungsalpene being absent you can also see the landscape as it was 7,000 years ago.


Circa (from Latin, meaning 'around, about') – frequently abbreviated c., ca. or ca and less frequently circ. or cca. – signifies "approximately" in several European languages and as a loanword in English, usually in reference to a date. Circa is widely used in historical writing when the dates of events are not accurately known.

When used in date ranges, circa is applied before each approximate date, while dates without circa immediately preceding them are generally assumed to be known with certainty.


1732–1799: Both years are known precisely.

c. 1732 – 1799: The beginning year is approximate; the end year is known precisely.

1732 – c. 1799: The beginning year is known precisely ; the end year is approximate.

c. 1732 – c. 1799: Both years are approximate.


An epoch, for the purposes of chronology and periodization, is an instant in time chosen as the origin of a particular calendar era. The "epoch" serves as a reference point from which time is measured.

The moment of epoch is usually decided by congruity (makes simple sense), or by following conventions understood from the epoch in question. The epoch moment or date is usually defined from a specific, clear event of change, epoch event. In a more gradual change, a deciding moment is chosen when the epoch criterion was reached.

Global temperature record

The global temperature record shows the fluctuations of the temperature of the atmosphere and the oceans through various spans of time. The most detailed information exists since 1850, when methodical thermometer-based records began. There are numerous estimates of temperatures since the end of the Pleistocene glaciation, particularly during the current Holocene epoch. Older time periods are studied by paleoclimatology.


The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years before present, after the last glacial period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene together form the Quaternary period. The Holocene has been identified with the current warm period, known as MIS 1. It is considered by some to be an interglacial period within the Pleistocene Epoch.The Holocene has seen the growth and impacts of the human species worldwide, including all its written history, development of major civilizations, and overall significant transition toward urban living in the present. Human impacts on modern-era Earth and its ecosystems may be considered of global significance for future evolution of living species, including approximately synchronous lithospheric evidence, or more recently hydrospheric and atmospheric evidence of human impacts. In July 2018, the International Union of Geological Sciences split the Holocene epoch into three distinct subsections, Greenlandian (11,700 years ago to 8,326 years ago), Northgrippian (8,326 years ago to 4,200 years ago) and Meghalayan (4,200 years ago to the present), as proposed by International Commission on Stratigraphy. The boundary stratotype of Meghalayan is a speleothem in Mawmluh cave in India, and the global auxiliary stratotype is an ice core from Mount Logan in Canada.The name Holocene comes from the Ancient Greek words ὅλος (holos, whole or entire) and καινός (kainos, new), meaning "entirely recent".

Holocene calendar

The Holocene calendar, also known as the Holocene Era or Human Era (HE), is a year numbering system that adds exactly 10,000 years to the currently dominant (AD/BC or CE/BCE) numbering scheme, placing its first year near the beginning of the Holocene geological epoch and the Neolithic Revolution, when humans transitioned from a hunter-gatherer lifestyle to agriculture and fixed settlements. The year 2019 in the Holocene calendar is 12019 HE. The HE scheme was first proposed by Cesare Emiliani in 1993 (11993 HE).

Homo luzonensis

Homo luzonensis is an extinct species of primitive human in the genus Homo. In 2007, a third metatarsal bone (MT3) was discovered in Callao Cave, Luzon, Philippines by Philip J. Piper and initially identified as modern human by Florent Détroit. This find was dated using uranium series ablation to an age of 66,700 ± 1000 years before present, while associated faunal remains and a hominin tooth found in 2011 delivered dates of around 50,000 years ago.In 2019, Florent Détroit et al. described the subsequent discovery of "twelve additional hominin elements that represent at least three individuals that were found in the same stratigraphic layer of Callao Cave as the previously discovered metatarsal" and identified the fossils as belonging to a newly discovered species, Homo luzonensis, on the basis of differences from previously identified species in the genus Homo. This included H. floresiensis and H. sapiens. However, some scientists think additional evidence is required to confirm the fossils as a new species, rather than a locally adapted population of other Homo populations, such as H. erectus.

Horr's Island archaeological site

The Horr's Island archaeological site is a significant Archaic period archaeological site located on an island in Southwest Florida formerly known as Horr's Island. Horr's Island (now called Key Marco, not to be confused with the archaeological site Key Marco) is on the south side of Marco Island in Collier County, Florida. The site includes four mounds and a shell ring. It has one of the oldest known mound burials in the eastern United States, dating to about 3400 radiocarbon years Before Present (BP). One of the mounds has been dated to as early as 6700 BP. It was the largest known community in the southeastern United States to have been permanently occupied during the Archaic period (8000 BCE-1000 BCE).

The island is named for Capt. John Foley Horr, who raised pineapples on the island in the late 19th century. The Capt. John Foley Horr House was listed on the U.S. National Register of Historic Places on October 8, 1997. In the late 1980s, a development company planned to build a bridge to Horr's Island and develop it. In response to state law requiring an archaeological assessment of the island before it could be developed, the development company funded a research project. The research team carried out excavations for three months.

List of volcanoes in India

This is a list of Quaternary active, dormant/extinct volcanoes in India.


Millets (/ˈmɪlɪts/) are a group of highly variable small-seeded grasses, widely grown around the world as cereal crops or grains for fodder and human food.

Millets are important crops in the semiarid tropics of Asia and Africa (especially in India, Mali, Nigeria, and Niger), with 97% of millet production in developing countries. The crop is favored due to its productivity and short growing season under dry, high-temperature conditions.

Millets are indigenous to many parts of the world. The most widely grown millet is pearl millet, which is an important crop in India and parts of Africa. Finger millet, proso millet, and foxtail millet are also important crop species.

Millets may have been consumed by humans for about 7,000 years and potentially had "a pivotal role in the rise of multi-crop agriculture and settled farming societies".

Pinza-Abu Cave Man

The Pinza-Abu Cave Man (ピンザアブ洞人, Pinza-Abu Dōjin) is a prehistoric people known from bones found in the Pinza-Abu Cave, near Ueno in Miyako Island, southern Japan. The remains appear to have the modern man anatomical type and have been dated to about 30,000 years ago, i.e. 25,800 ± 900 and 26,800 ± 1,300 before present. The name "Pinza-Abu" literally means "goat cave" in the local Miyako language.


The Pleistocene ( , often colloquially referred to as the Ice Age) is the geological epoch which lasted from about 2,588,000 to 11,700 years ago, spanning the world's most recent period of repeated glaciations. The end of the Pleistocene corresponds with the end of the last glacial period and also with the end of the Paleolithic age used in archaeology.

The Pleistocene is the first epoch of the Quaternary Period or sixth epoch of the Cenozoic Era. In the ICS timescale, the Pleistocene is divided into four stages or ages, the Gelasian, Calabrian, Middle Pleistocene (unofficially the 'Chibanian') and Upper Pleistocene (unofficially the 'Tarantian'). In addition to this international subdivision, various regional subdivisions are often used.

Before a change finally confirmed in 2009 by the International Union of Geological Sciences, the time boundary between the Pleistocene and the preceding Pliocene was regarded as being at 1.806 million years Before Present (BP), as opposed to the currently accepted 2.588 million years BP: publications from the preceding years may use either definition of the period.


Sollipulli (Spanish pronunciation: [soʝiˈpuʝi]; lit. reddish mountain in the Mapuche language) is an ice-filled volcanic caldera and volcanic complex, which lies southeast of the small town of Melipeuco in the La Araucanía Region, Chile. It is part of the Southern Volcanic Zone of the Andes, one of the four volcanic belts in the Andes chain.

The volcano has evolved in close contact with glacial ice. It differs from many calderas in that Sollipulli appears to have collapsed in a non-explosive manner. The age of collapse is not yet known, but it is presently filled with ice to thicknesses of 650 m (2,130 ft). The ice drains through two glaciers in the west and the north of the caldera. Sollipulli has developed on a basement formed by Mesozoic and Cenozoic geological formations.

Sollipulli was active in the Pleistocene and Holocene epochs. A large Plinian eruption occurred 2,960–2,780 years before present, forming the Alpehué crater and generating a high eruption column and ignimbrite deposits. The last activity occurred 710 ± 60 years before present and formed the Chufquén scoria cone on the northern flank. Sollipulli is among the 118 volcanoes which have been active in recent history.

Key topics
Astronomic time
Geologic time
Genetic methods
Linguistic methods
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