a. That part of any structure that is below ground, more particularly the
foundations. The latter may take many forms, according to the nature and
bearing strength of the ground. Hammond
b. The lower portion of a structure upon which something else is built up.
Crispin

a. The zone below the surface, in which geologic features, principally
stratigraphic and structural, are interpreted on the basis of drill
records and various kinds of geophysical evidence. AGI
b. Rock and soil materials lying beneath the Earth's surface.--adj. Formed
or occurring beneath a surface, esp. beneath the Earth's surface.
CF:surficial
c. An underground workplace. Long

subsurface contour

See:structure contour

subsurface correlation

Correlation of rock units and structures that do not appear at the
surface, by means of well logs, mine maps, and geophysical data.
Stokes

subsurface corrosion

Formation of isolated particles of corrosion products beneath the metal
surface. This results from the preferential reaction of certain alloy
constituents by inward diffusion of oxygen, nitrogen, and sulfur.
ASM, 1

subsurface geology

Geology and correlation of rock formations, structures, and other features
beneath the land or sea-floor surface as revealed or inferred by
exploratory drilling, underground workings, and geophysical methods.
CF:surface geology

subsurface injection

See:subsurface waste disposal

subsurface map

a. A map depicting geologic data or features below the Earth's surface;
esp. a plan of mine workings, or a structure-contour map of a petroleum
reservoir or an underground ore deposit, coal seam, or key bed.
AGI
b. A plane surface representation, generally in horizontal projection, of
geologic data or features beneath the Earth's surface. There are many
types of subsurface maps, such as structure contour maps, isopachous maps,
and maps showing variations in lithology, or proportions of different
types of lithology in rocks not exposed at the surface. Stokes

subsurface waste disposal

Waste disposal in which manufacturing wastes are deposited in porous
underground rock formations. Disposal wells should be at least 200 ft (61
m) deeper than the deepest water-bearing formation, and they must be
sealed with cement from top to bottom. Also called subsurface injection.

subsurface water

Water in the lithosphere in solid, liquid, or gaseous form. It includes
all water beneath the land surface and beneath bodies of surface water.
Syn:subterranean water; under ground water; ground water. AGI

subtense bar

A horizontal bar used in the subtense system of surveying by tacheometry.
It is held at a distant point and its distance is calculated from its
known length and the angle that it subtends at the observer's eye.
See also:tachymeter

subterrain

See:subterrane

subterrane

The bedrock beneath a surficial deposit or below a given geologic
formation. Syn:subterrain

subterranean

Formed or occurring beneath the Earth's surface, or situated within the
Earth. CF:subaerial
subterrane. AGI

subterranean stream

A body of subsurface water flowing through a cave or a group of
communicating caves, as in a karstic region. AGI

subterranean water

See:ground water; subsurface water.

subterrestrial

See:subterranean