In a coal mine, atmosphere containing poisonous gases or a lack of
sufficient oxygen as a result of combustible gases explosions, coal-dust
explosions, combined gas and dust explosions, or mine fires, and which can
only be entered by persons wearing breathing apparatus. McAdam, 1
See:P wave; compressional wave.
A nearly obsolete syn. of intrusion. AGI
Line of equal value of an anomaly. Schieferdecker
Obsolete type of shaking table. Pryor, 3
See:ilmenorutile
An orthorhombic mineral, (U,Fe,Y,Ca)(Nb,Ta)4 (?) ; opaque black; at
Ishikawa, Iwaki Province, Japan.
Transparent sheet mica, commonly muscovite, principally from pegmatite
dikes. See also:mica; muscovite.
A group of islands having a curving, arclike pattern. Most island arcs lie
near the continental masses, but inasmuch as they rise from the deep ocean
floors, they are not a part of the continents proper. Stokes
a. A term for lines of equal volatile content (now called isovols) drawn
on a map or diagram. Tomkeieff
b. Lines of equal C:H ratio in coal drawn on the map or diagram.
Tomkeieff
An imaginary line or a line on a map or chart connecting or marking places
on the surface of the Earth where the height of the barometer reduced to
sea level is the same either at a given time or for a certain period.
Webster 3rd
A term used for a line that connects all areas of equal uplift or
depression; it is used esp. in Quaternary geology as a means for
expressing crustal movements related to postglacial uplift. AGI
a. A line on a map or chart that connects points of equal water depth.
Syn:bathymetric contour; depth contour. AGI
b. An imaginary line on a land surface along which all points are the same
vertical distance above the upper or lower surface of an aquifer or above
the water table. AGI
Lines of equal calorific value in coal drawn on a map or diagram.
Tomkeieff
On a map or diagram, a line connecting points of equal fixed-carbon
content in coal. See also:isocarbon map
A map showing, by contours, the areas having an equal quantity of carbon
within an assumed interval of stratigraphic section. See also:isocarb
Ballard
a. A line drawn on a map through points of equal drilled thickness for a
specified subsurface unit. Thickness figures are uncorrected for dip in
vertical wells, and corrected for hole angle, but not for dip, in deviated
wells. CF:isopach
b. In a phase diagram, a line connecting points of constant volume.
AGI
A map showing drilled thickness of a given stratigraphic unit by means of
isochores. Syn:convergence map
2 þÍB ÐB æ¹î Ì DICTIONARY TERMS:isochromatic lines In stress analysis by the photoe
[\B]isochromatic lines[\N]
A contour map that depicts the continuity and extent of color stains on
geologic formations. AGI
See:isochronous
Lines connecting points of equal times. When the relative seismic
velocities are known, the isochrones can be translated into depth
contours. See also:refraction shooting