In situIn situ (ɪn_ˈsɪtjuː,_-ˈsaɪtjuː,-_ˈsiː-; often not italicized in English) is a Latin phrase that translates literally to "on site" or "in position." It can mean "locally", "on site", "on the premises", or "in place" to describe where an event takes place and is used in many different contexts. For example, in fields such as physics, geology, chemistry, or biology, in situ may describe the way a measurement is taken, that is, in the same place the phenomenon is occurring without isolating it from other systems or altering the original conditions of the test.
Conchoidal fractureConchoidal fracture describes the way that brittle materials break or fracture when they do not follow any natural planes of separation. Mindat.org defines conchoidal fracture as follows: "a fracture with smooth, curved surfaces, typically slightly concave, showing concentric undulations resembling the lines of growth of a shell". Materials that break in this way include quartz, chert, flint, quartzite, jasper, and other fine-grained or amorphous materials with a composition of pure silica, such as obsidian and window glass, as well as a few metals, such as solid gallium.
Luminescence datingLuminescence dating refers to a group of methods of determining how long ago mineral grains were last exposed to sunlight or sufficient heating. It is useful to geologists and archaeologists who want to know when such an event occurred. It uses various methods to stimulate and measure luminescence. It includes techniques such as optically stimulated luminescence (OSL), infrared stimulated luminescence (IRSL), and thermoluminescence dating (TL). "Optical dating" typically refers to OSL and IRSL, but not TL.
ChronologyChronology (from Latin chronologia, from Ancient Greek χρόνος, chrónos, "time"; and -λογία, -logia) is the science of arranging events in their order of occurrence in time. Consider, for example, the use of a timeline or sequence of events. It is also "the determination of the actual temporal sequence of past events". Chronology is a part of periodization. It is also a part of the discipline of history including earth history, the earth sciences, and study of the geologic time scale.
Common EraCommon Era (CE) and Before the Common Era (BCE) are year notations for the Gregorian calendar (and its predecessor, the Julian calendar), the world's most widely used calendar era. Common Era and Before the Common Era are alternatives to the original Anno Domini (AD) and Before Christ (BC) notations used for the same calendar era. The two notation systems are numerically equivalent: " CE" and "AD " each describe the current year; "400 BCE" and "400 BC" are the same year.
Natural (archaeology)In archaeology, natural is a term to denote a layer (stratum) in the stratigraphic record where there is no evidence of human impact on the environment. While there may be "natural" layers interbedded with archaeologically interesting layers, such as when a site was abandoned for long periods between occupations, the top (or horizon) of the natural layer below which there is no anthropogenic activity on site, and thus where the archaeological record begins, is the point to terminate digging.
Megalithic architectural elementsThis article describes several characteristic architectural elements typical of European megalithic (Stone Age) structures. In archaeology, a forecourt is the name given to the area in front of certain types of chamber tomb. Forecourts were probably the venue for ritual practices connected with the burial and commemoration of the dead in the past societies that built these types of tombs. In European megalithic architecture, forecourts are curved in plan with the entrance to the tomb at the apex of the open semicircle enclosure that the forecourt creates.
