Historical Geology Understanding Our Planet\'s Past

(Marvins-Underground-K-12) #1

greenstone a g reen, weakly formed, metamorphic igneous rock
greenstone belt a mass of Archean metamorphosed igneous rock
gypsum a white , colorless calcium sulfate mineral formed during the evap-
oration of brine pools; when calcined, it forms plaster of Paris
Hallucigenia(HA-loose-ah-gen-ia) an unusual animal of the early Cam-
brian with stiltlike legs and multiple mouths along the back
hexacoral coral with six-sided skeletal walls
horn a peak on a mountain formed by glacial erosion
hydrocarbon a molecule consisting of carbon chains with attached hydro-
gen atoms
Iapetus Sea(EYE-ap-I-tus) a former sea that occupied a similar area as the
present Atlantic Ocean prior to the assemblage of Pangaea
ice age a per iod of time when large areas of Earth were covered by massive
glaciers
ichthyosaur(IK-the-eh-sore) an extinct Mesozoic aquatic reptile with a
streamlined body and long snout
Ichth yostega (IK-the-eh-ste-ga) an extinct primitive Paleozoic fishlike
amphibian
impact the point on the surface upon which a celestial object lands
index fossil a r epresentative fossil that identifies the rock strata in which it
is found
interglacial a w arming period between glacial periods
inverte brate an animal with an external skeleton such as shellfish and insects
iridium a rar e isotope of platinum, relatively abundant on meteorites
island arc volcanoes landward of a subduction zone parallel to a trench and
above the melting zone of a subducting plane
karst a ter rain comprised of numerous sinkholes in limestone
lacustrine(leh-KES-trene) inhabiting or produced in lakes
Laurasia(lure-AY-zha) a northern supercontinent of Paleozoic time, con-
sisting of North America, Europe, and Asia
Laurentia(lure-IN-tia) an ancient North American continent
lava molten magma that flows out onto the surface
limestone a sedimentary rock composed of calcium carbonate secreted
from seawater by invertebrates and whose skeletons compose the bulk of
deposits
lithosphere(LI-tha-sfir) the rocky outer layer of the mantle that includes
the terrestrial and oceanic crusts;the lithosphere circulates between
Earth’s surface and mantle by convection currents
lithospheric a segment of the lithosphere, the upper layer plate of the man-
tle, involved in the interaction of other plates in tectonic activity
loess a thick deposit of airborne dust
lungfish a bon y fish that breathes on land and in water


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