Glossary of Geological Terms
Agate: quartz mineral with characteristic banding, form of the Chalcedony;
mostly in cavities of eruptive rocks (melaphyr-mandelstones; e.g. Idar-Oberstein).
Ammonites: extinct group of cephalopods with outer calcareous shell. The
shell was usually curled into a spiral. Many ammonites are excellent guide fossils;
they occured from the
Lower Devon until the end of the
Cretaceous era; there are more than 5000 species.
Amphiboles: rock-forming group of minerals; containing magnesium, iron,
calcium, sodium, aluminum or titanium.
Andesite: medium to dark gray, often porphyritic eruptive rock with
fine-grained, partly glassy groundmass with inclusions of plagioclase, biotite,
hornblende or pyroxenes.
Aragonite: rock very similar to calcite (CaCO3); component of the
shells and skeletons of many animals.
Arkose: sandstone with a high proportion of feldspars (over 25%) and mica;
formed under dry-hot conditions by weathering of Rocks rich in such minerals
(e.g., gneiss and granite).
Belemnites: extinct order of cephalopods from the
Lower Carboniferous until the
Upper Chalk. They had an elongated body with
an internal skeleton. Mostly only the massive, pointed body end ("thunderbolts")
has been preserved. Important guide fossils for the
Jurasic und
Cretaceous eras.
Biotite: dark green or brown to black mineral from the group of of
the mica.
Breccia: coarse-grained sedimentary rock; consolidated debris composed
of angular pieces of rock and minerals cemented by clayey, calcareous, or
siliceous binders.
Bruchtektonik (Fracture tectonics): fracturing and dislocation phenomena
of the earth's crust, associated with the formation of fractures, fissures,
and faults.
Bunte Schiefer (Variegated slate): oldest
Devonian
strata in the Hunsrück; mainly composed of clay, but can also consist of
coarse rubble.
Calcite (Kalkspat): mostly transparent, white mineral of the chemical
composition CaCO3 (calcium carbonate); frequently occurring, often rock-forming.
Chalcedony: cryptocrystalline variety of quartz; multicolored or
colorless, translucent.
Dacite: silica-rich eruptive rock with plagioclase inclusions, quartz,
biotite, hornblende and others in dense, partly glassy groundmass.
Diorite: light, granular bedrock.
Dolomite: granular to dense layered rock, which consists mainly
of magnesium carbonate and calcite; weathered in very characteristic form
(e.g., Dolomites in South Tyrol).
Druse: cavity in rocks lined with crystals.
Einsprengling (Inclusion): larger single crystal in the groundmass
of magmatic rocks.
Ergussgestein (Volcanic rock: Vulcanites): magmatic rocks, which are
formed in the course of volcanic activity by solidification of the liquid
magma from the earth's interior on the earth's surface.
Erosion: removal of the earth's surface, especially by the incising
and clearing out activity of the flowing water.
Eruption: collective term for volcanic eruptive activity, in particular
the outflow of liquid magma from the earth's interior to the earth's surface.
Faltung (Folding): upward and downward bending of rock strata caused
by lateral pressure and constriction of rock layers.
Faulschlamm (Sapropel): black sludge at the bottom of nutrient-rich
waters; very rich in fat and protein; precursor of petroleum formation.
Facies (Metamorphic facies): features that are characteristic of the
formation of a sedimentary rock.
Feldspars: group of rock-forming silicates; subdivisible into alkali
feldspars and plagioclases.
Fossils: remains of animals or plants (also their traces of life)
from the geological past.
Gebirgsbildung (Orogenesis: Mountain building): deformation of
limited areas of the earth's crust caused by uplift and subsidence processes;
with rock displacements, folding, fracture tectonics, volcanism and earthquakes
leading to surface forms with high relief energy. It is primarily caused
by movements of the earth's mantle.
Geology: study of the origin, development and change of the earth and
the living creatures inhabiting it in geological time.
Geosyncline: extensive subsidence area of the earth's crust in which
large quantities of sedimentary rocks accumulate. These can later, after folding,
be lifted out as mountains.
Gesteine (Rocks): natural, solid formations within the earth's crust;
according to their formation, a distinction is made between igneous,
sedimentary and metamorphic rocks.
Glimmer (Mica): flake-like silicates.
Gneiss: group of metamorphic rocks with quartz, feldspar and mica
as main constituents; formed from igneous rocks (ortogneiss) or
sedimentary rocks (paragneiss).
Granite: in terms of quantity, the most common deep rock with the
main constituents of feldspar, quartz and mica; occurs in the form of
thick massifs (boulders) as well as in veins.
Greenschist: weakly metamorphic, fine-grained rocks with a
schistose structure; they are formed from clay-marly sedimentary rocks
or basic igneous rocks.
Grus (Rock debris): fine rock debris formed by weathering.
Härtling (Hard rock): elevation outstanding above its surroundings
due to its resistance to erosion and weathering.
Hornblende: important mineral from the group of amphiboles; main
component of many rocks, e.g. of the hornblende slate.
Intrusion: process of penetration and solidification of magma
in rocks of the earth's solid crust.
Kalkspat (Calcite): mostly transparent, white mineral of the chemical
composition CaCO3 (calcium carbonate). composition CaCO3 (calcium carbonate);
frequently occurring, often rock-forming.
Kalkstein (Limestone): sedimentary rock consisting predominantly
of calcite, but also of aragonite or dolomite; forms by chemical precipitation
or from lime shells and skeletons of animals or plant organisms.
Kies (Gravel): crushed, sedimentary unconsolidated rock; consists
of rock fragments or ice rounded rock fragments.
Klastische Gesteine (Clastic rocks, debris rocks): sedimentary rocks
that have been formed from the fragments of older rocks.
Konglomerat (Conglomerate): coarse-grained sedimentary rock consisting
of rounded rock fragments (boulders), which are cemented by clayey,
calcareous, siliceous or ferruginous binders.
Kontaktmetamorphose (Contact metamorphism): rock transformation that
has been caused by contact with rising hot magma.
Korrosion (Corrosion): decomposition of rocks by the chemical action
of water and the acids, bases and salts dissolved in it.
Lava: the hot magma escaping to the earth's surface from vents
and fissures during volcanic eruptions; also a term for the resulting rock mass.
The solidification forms depend on temperature, viscosity (flowability) and gas
content of the molten rock.
Leitfossilien (Guide fossils): fossil animal and plant species ("fossils")
that are characteristic of geological strata or strata sequences with the same
geological age.
Liparite (Rhyolite): light gray, reddish or greenish eruptive rock with
inclusions of plagioclase, quartz, biotite and others in an often glassy groundmass;
geologically older rhyolite is called quartz-porphyry.
Magma: glowing, liquid, predominantly silicate (consisting of silicates)
melt from the depths of the earth. One distinguishes between the processes of the
volcanism at or directly under the earth's surface and the processes of plutonism,
which take place at greater depths.
Magmatic rocks (Magmatites): the rocks formed by solidification of magma.
A distinction is made between volcanic rocks (e.g. basalt), plutonites (e.g. Granite)
and the intermediate gangue rocks.
Magmatite (Magmatic rocks): the rocks formed by solidification of magma.
A distinction is made between volcanic rocks (e.g. basalt), plutonites (e.g. Granite)
and the intermediate gangue rocks.
Melaphyre: igneous rock of basaltic composition; usually of dark or dark green
color, often weathering reddish; melaphyre mandelstones yield agates (e.g., in
Idar-Oberstein)).
Mergel (Marl): stratified rocks consisting mainly of clay and limestone (clay
marl and lime marl).
Metamorphic rocks: the rocks formed by metamorphism; unlike "ortho-rocks"
which originate from igneous rocks (e.g., granites), "para-rocks" are formed from
sediments, e.g. quartzites, marbles, schists, gneisses.
Metamorphism: the transformation and reshaping of a rock by high pressure
and temperature.
Minerals: the constituents of rocks that are uniform in terms of their
physical and chemical properties.
Moraine: the rock material carried and deposited by glaciers.
Nepheline: feldspar representative; common in basalts.
Olivine: group of rock-forming minerals.
Orogenesis (Mountain building): deformation of
limited areas of the earth's crust caused by uplift and subsidence processes;
with rock displacements, folding, fracture tectonics, volcanism and earthquakes
leading to surface forms with high relief energy. It is primarily caused
by movements of the earth's mantle.
Paleontology: includes the branches of science that deal with the study
of the ancient animal and plant world.
Phyllite: greenish-gray, silky shiny, fine-foliated shale; formed by
metamorphosis from clay shales.
Plagioclase: rock-forming mineral from the feldspar group.
Plutonism: formation, alteration and migration of natural rock melts
within the Earth's crust; the solidified rocks at greater depths are called
deep rocks or "plutonites"; large deep rock bodies in the earth's crust are
called "plutons".
Plutonite (Deep rocks): igneous rocks, which are formed by the
solidification of magma in the deeper crust of the earth.
Porphyry: collective term for igneous rocks with individual larger
crystals (mostly alkali feldspars and/or quartz) as inclusions in a
fine-grained and dense groundmass. The term is used today only in compositions,
e.g. quartz porphyry or granite porphyry.
Pyrite (Sulfur pyrite): common mineral in ore deposits.
Pyroxenes: group of rock-forming minerals; mostly green or brown to black;
crystals mostly columnar to stalked.
Quartz: group of important rock-forming minerals; always present in
crystallized form.
Quartzite: very hard, mostly dense, fine-grained, mainly of Quartz,
metamorphic rock; it formed from sandstone (also called called rock quartzite).
Quartz porphyry: reddish colored eruptive rock; occurs in the
Red-Lying era.
Rhyolith (Liparite): light gray, reddish or greenish eruptive rock with
inclusions of plagioclase, quartz, biotite and others in an often glassy groundmass;
geologically older rhyolite is called quartz-porphyry.
Sandstone: sedimentary rock consisting largely of quartz grains, cemented
by a clayey, siliceous or ferruginous binder.
Sapropel (Faulschlamm): black sludge at the bottom of nutrient-rich
waters; very rich in fat and protein; precursor of petroleum formation.
Schicht (Layer): a rock body of areal extent formed by deposition.
Individual layers are separated from each other by bedding joints.
Schiefer (Slate): a rock formed by tectonic processes and metamorphism;
in thin, flat plates breaking rock.
Sedimentation: process of separating or settling solid substances
that are transported by water.
Sedimentary rock (Layered rock): a rock formed by the consolidation
of sediments; clastic sediments consist of mechanically crushed rock fragments
of various grain sizes; chemical sediments are formed by precipitation of dissolved
constituents from fluids; biogenic sediments form under substantial participation
of animal or vegetable organisms.
Silicates: the most important rock-forming minerals of the earth (silicon);
they include quartz, feldspar and mica.
Störung (Discontinuity): separation joint where an adjustment of two
rock layers has taken place.
Syncline: depression in a geological fold.
Taunus quartzite: relief-determining quartzite in Hunsrück with high
quartz content; difficult to weather.
Tectonics: branch of geology that deals with the structure of the
earth's crust and the movements and forces that affect the earth's crust.
Tiefengesteine (Plutonite): igneous rocks, which are formed by the
solidification of magma in the deeper crust of the earth.
Tone (Clays): fine-grained, clastic unconsolidated rocks that
consist mainly of clay minerals, which are newly formed during weathering.
Tonschiefer (Clay schist): thin-slate clay rock that splits into
flat plates along parallel cleavage planes; formed by tectonic pressure
and slight metamorphosis from slate clay (e.g. roofing slate).
Trümmergesteine (Debris rocks, clastic rocks): sedimentary rocks
that have been formed from the fragments of older rocks.
Tuff: solidified volcanic ash.
Verwerfung (Discontinuity): the relative displacement of two rock
layers along the length of a fault.
Verwitterung (Weathering): the decay of rocks and minerals at or
near the earth's surface caused by the action of physical-mechanical,
chemical, and biological influences. Type and intensity of weathering
depend on rock and climate. Weathering is a prerequisite for the
formation of sedimentary rocks and the formation of soil.
Volcanism: all geological processes associated with the escape
of solid, liquid or gaseous substances from the earth's interior to the
surface. Volcanic activity occurs mainly in tectonic zones of weakness
(e.g., faults), or at stable melting zones in the Earth's mantle
("hot spots").
Volcanic rocks (Eruptive rocks): igneous rocks formed during
volcanic activity by solidification of the liquid magma at the
earth's surface.