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GLOSSARY /207/es/MHDQ243/tiL12214_disk1of1/0073512214/tiL12214_pagefiles

A with a knife and that react violently with the time interruption unconformity are
water to form an alkaline solution not parallel, meaning probable tilting or
absolute humidity a measure of the actual
alkaline earth metals members of family folding followed by a significant period of
amount of water vapor in the air at a given
IIA of the periodic table, having common erosion, which in turn was followed by a
time—for example, in grams per cubic
properties of soft, reactive metals that are period of deposition
meter
less reactive than alkali metals annular eclipse event that occurs when the
absolute magnitude a classification scheme
alkane a hydrocarbon with a single covalent penumbra reaches the surface of Earth; as
to compensate for the distance differences
bond between the carbon atoms seen from Earth, the Sun forms a bright
to stars; calculations of the brightness that
alkene a hydrocarbon with a double covalent ring around the disk of the new moon
stars would appear to have if they were at a
carbon-carbon bond Antarctic Circle the parallel identifying the
defined standard distance
alkyne a hydrocarbon with a carbon-carbon limit toward the equator where the Sun ap-
absolute zero the theoretical lowest tem-
triple bond pears above the horizon all day for at least
perature possible, which occurs when all
allotropic forms elements that can have one day during the summer; located at
random motion of molecules has ceased
several different structures with different 66.5°S latitude
abyssal plain the practically level bottom of
physical properties—for example, graphite anticline an arch-shaped fold in layered
the ocean floor
and diamond are two allotropic forms of bedrock
acceleration a change in velocity per change
carbon anticyclone a high-pressure center with
in time; by definition, a change in velocity
alpha particle the nucleus of a helium atom winds flowing away from the center; asso-
can result from a change in speed, a change
(two protons and two neutrons) emitted as ciated with clear, fair weather
in direction, or a combination of changes
radiation from a decaying heavy nucleus; antinode the region of maximum amplitude
in speed and direction
also known as an alpha ray between adjacent nodes in a standing wave
accretion disk a fat bulging disk of gas and
alpine glaciers glaciers that form at high el- apogee the point at which the Moon’s el-
dust from the remains of the gas cloud that
evations in mountainous regions liptical orbit takes the Moon farthest from
forms around a protostar
alternating current an electric current that Earth
achondrites homogeneously textured stony
moves first in one direction, then in the op- apparent local noon the instant when the
meteorites
posite direction with a regular frequency Sun crosses the celestial meridian at any
acid any substance that is a proton donor
amino acids organic functional groups that particular longitude
when dissolved in water; generally consid-
form polypeptides and proteins apparent local solar time the time found
ered a solution of hydronium ions in water
amp a unit of electric current; equivalent from the position of the Sun in the sky; the
that can neutralize a base, forming a salt
to C/s shadow of the gnomon on a sundial
and water
ampere the full name of the unit amp apparent magnitude a classification scheme
acid-base indicator a vegetable dye used to
amplitude the extent of displacement from for different levels of brightness of stars
distinguish acid and base solutions by a
the equilibrium condition; the size of a that you see; brightness values range from
color change
wave from the rest (equilibrium) position 1 to 6 with the number 1 (first magnitude)
air mass a large, more or less uniform body
angle of incidence the angle of an incident assigned to the brightest star and the num-
of air with nearly the same temperature and
(arriving) ray or particle to a surface; mea- ber 6 (sixth magnitude) assigned to the
moisture conditions throughout
sured from a line perpendicular to the sur- faintest star that can be seen
air mass weather the weather experienced
face (the normal) apparent solar day the interval between two
within a given air mass; characterized by
angle of reflection the angle of a reflected consecutive crossings of the celestial me-
slow, gradual changes from day to day
ray or particle from a surface; measured ridian by the Sun
alcohol an organic compound with a gen-
from a line perpendicular to the surface aquifer a layer of sand, gravel, or other
eral formula of ROH, where R is one of the
(the normal) highly permeable material beneath the sur-
hydrocarbon groups—for example, methyl
angular momentum quantum number in face that is saturated with water and is ca-
or ethyl
the quantum mechanics model of the atom, pable of producing water in a well or spring
aldehyde an organic molecule with the gen-
one of four descriptions of the energy state Archean a block of time of 4,000 to 2,500
eral formula RCHO, where R is one of the
of an electron wave; this quantum number million years before the present; one of
hydrocarbon groups—for example, methyl
describes the energy sublevels of electrons three Precambrian eons before the time of
or ethyl
within the main energy levels of an atom visible life
alkali metals members of family IA of the
angular unconformity a boundary in rock Arctic Circle the parallel identifying the
periodic table, having common properties
where the bedding planes above and below limit toward the equator where the Sun
of shiny, low-density metals that can be cut
G-1