(View exact match)coringCATEGORY: technique
DEFINITION: Driving a hollow tube into the ground to get a stratigraphic sample of the subsoil.
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coreSYNONYMS OR RELATED TERMS: coring
DEFINITION: A black or gray zone in the interior cross-section of a vessel wall, usually associated with incomplete removal of carbonaceous matter from the clay during relatively low-temperature firing; not to be confused with black coring at high temperatures, which results from trapped gases and may lead to bloatingcore samplingSYNONYMS OR RELATED TERMS: coring
DEFINITION: A subsurface detection technique using a hollow metal tube driven into the ground to lift a column of earth for stratigraphic study. This technique is used in underground or undersea exploration. A core sample is a roughly cylindrical piece of subsurface material removed by a special drill and brought to the surface for examination. Such a sample reveals the properties of underground rock, such as its porosity and permeability and allows investigation of the features of a given strata.handle attachmentCATEGORY: artifact
DEFINITION: Pot-supported, scoring and slip, slippiston corerCATEGORY: tool
DEFINITION: A device for extracting columns of sediment from the ocean floor. Deeper cores are taken by the piston corer, which can take samples as long as 20 meters. In a piston corer, a closely fitted piston attached to the end of the lowering cable is installed inside the coring tube. When the coring tube is driven into the ocean floor, friction exerts a downward pull on the core sample. The hydrostatic pressure on the ocean bottom, however, exerts an upward pressure on the core that will work against a vacuum being created between the piston and the top of the core. The piston, in effect, provides a suction that overcomes the frictional forces acting between the sediment sample and the inside of the coring tube. The hydraulic piston corer is used by deep-sea drilling ships and can take undisturbed cores of lengths up to 200 meters. Dates for the different layers are obtained by radiocarbon, paleomagnetism, or uranium series methods.subsurface detectionCATEGORY: technique
DEFINITION: Remote sensing techniques carried out at ground level, and including bosing (or bowsing), augering, coring, Lerici periscope, resistivity detector, magnetometer, and radar techniques.tephrochronologySYNONYMS OR RELATED TERMS: tephrachronology
DEFINITION: A method for the relative dating of horizons in volcanic regions by identification of different layers of ash (tephra). Tephra layers (beds) are ideal stratigraphic markers because they are deposited instantaneously. Also, the chemical content of tephra (volcanic ash) is unique for each eruption. If artifacts lie below tephra known to have come from a certain eruption, the artifacts predate the eruption. Tephra layers may be dated by potassium-argon dating and fission track dating and they can sometimes be tied in to absolute chronology where radiocarbon dates can be obtained from material contemporary with the deposit. To establish a chronology it is necessary to identify and correlate as many tephra units as possible over the widest possible area. In the Mediterranean, deep-sea coring produced evidence for the ash fall from the eruption of Thera, and its stratigraphic position provided important information in the construction of a relative chronology. The identification of multiple tephra beds may give bracketing ages for intervening strata. Tephrochronology has also been used to date glacial advances, sea level changes, and alluvial fans.