fissure a large crack in the crust through which magma might escape from
a volcano
fluvial(FLUE-vee-al) stream-deposited sediment
foraminifer(FOR-eh-MI-neh-fer) a calcium carbonate-secreting organ-
ism that lives in the surface waters of the oceans; after death, their shells
form the primary constituents of limestone and sediments deposited
onto the seafloor
formation a combination of rock units that can be traced over distance
fossil any remains, impression, or traces in rock of a plant or animal of a pre-
vious geologic age
fossil fuel an energy source derived from ancient plant and animal life that
includes coal,oil, and natural gas; when ignited, these fuels release car-
bon dioxide that was stored in Earth’s crust for millions of years
fusulinid(FEW-zeh-LIE-nid) a group of extinct foraminiferans resembling
a grain of wheat
galaxy a large , gravitationally bound cluster of stars
gastrolith(GAS-tra-lith) a stone ingested by an animal used to grind food
gastropod(GAS-tra-pod) a large class of mollusks, including slugs and
snails,characterized by a body protected by a single shell that is often
coiled
genus in systematics, the category of plants and animals under family and
comprising several species
geologic column the total thickness of geologic units in a region
geothermal the generation of hot water or steam by hot rocks in Earth’s
interior
geyser(GUY-sir) a spring that ejects intermittent jets of steam and hot water
glacier a thick mass of moving ice occurring where winter snowfall
exceeds summer melting
Glossopteris(GLOS-opt-ter-is) a late Paleozoic plant that existed on the
southern continents but not on the northern continents, thereby con-
firming the existence of Gondwana
gneiss(nise) a foliated metamorphic rock with a similar composition as
granite
Gondwana (gone-DWAN-ah) a southern supercontinent of Paleozoic
time, comprised of Africa, South America, India, Australia, and Antarc-
tica; it broke up into the present continents during the Mesozoic era
granite a coarse-grained, silica-rich igneous rock consisting primarily of
quartz and feldspars
graptolite(GRAP-the-lite) extinct Paleozoic planktonic animals resem-
bling tiny stems
greenhouse effect the trapping of heat in the lower atmosphere principally
by water vapor and carbon dioxideHistorical Geology