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Absolute Zero The theoretical lowest temperature possible at which all molecular motion ceases. Absolute zero, 0 K or -273.15°C, has never been reached.
Acid Generally, a substance that reacts with bases to form a salt, several different definitions of acids have been proposed by different scientists (listed in parentheses). 1) (Arrhenius) a compound that releases hydrogen ions (H+) in solution; 2) (Brønsted-Lowry) a compound capable of donating hydrogen ions, 3) (Lewis) a compound that can accept a pair of electrons from a base.
Acid Rain Rain with a pH less than 5.
Activation Energy The energy required to initiate a chemical reaction or process, abbreviated Ea. For example, a cigarette lighter requires activation energy (provided in the form of a spark) to initiate the reaction of fuel with oxygen.
Adsorb To adhere in an extremely thin layer of molecules (as of gases, solutes, or liquids) to the surfaces of solid bodies or liquids with which a substance is in contact.
Aesthenosphere The semi-molten layer of the earth which starts at ~70-200 km depth and ends at 660 km depth. The aesthenosphere is part of the mantle, and is composed primarily of the rock peridotite. The aesthenosphere can flow very slowly, allowing rigid pieces of the lithosphere to move around on top of it.
Alcohol An organic compound containing a hydroxyl group. Common examples include methanol (CH3OH) and ethanol (CH3CH2OH).
Alkanes A group of hydrocarbons with the general formula CnH(2n+2). Alkanes contain no carbon-carbon multiple bonds; common examples include methane and propane.
Alkenes A group of hydrocarbons with the general formula CnH(2n). Alkenes contain at least one carbon-carbon double bond; common examples include ethylene.
Alkyne A group of hydrocarbons with the general formula CnH(2n-2). Alkynes contain at least one carbon-carbon triple bond; common examples include ethyne also known as acetylene.
Allele A variation of a genetic element, usually resulting in a distinct trait.
Alpha Particle A type of particle that is ejected from radioactive nuclei. Alpha particles consist of two protons and two neutrons and thus are equivalent to helium nuclei.
Alveolar Pertaining to an alveolus.
Alveoli The plural of alveolus.
Alveolus A small sac-like structure in the body, especially common in the lung. A lung alveolus has extremely thin walls that aid in the exchange of gases including O2 and CO2.
Amino Acid Biochemical molecules that contain at least one amine group (-NH2) and at least one carboxylic acid group (-COOH) and conform to the general formula NH2-R-COOH, where R is an organic molecule. Amino acids are essential basic building blocks of proteins.
Amphibious Having the ability to live both on land and in water.
Andean Margin A convergent plate boundary, where oceanic crust is being subducted beneath continental crust. Named after the Andes Mountains in South America, which are the classic example of a continent-ocean convergence.
Andesite An extrusive igneous rock of intermediate composition, often gray in color. The main minerals present in andesite are plagioclase and hornblende. The word “andesite” comes from the Andes Mountains in South America, where this rock type is common. Around the world, andesitic magma erupts out of volcanoes along convergent boundaries, and its intrusive equivalent is diorite.
Angstrom (Ångstrom) A unit of length equivalent to 10-10 meters. 1Å = 0.0000000001 m.
Anion An ion that migrates to the anode in an electrical cell; a negatively charged ion.
Anode A positively charged terminal in an electrical cell.
Anther Male part of a flowering plant that holds pollen.
Aquifer A porous and permeable body of rock or sediment through which groundwater flows.
Atom The smallest unit of an element that retains the chemical properties of the element. Atoms can exist alone or in combinations with other atoms forming molecules.
Atomic Mass The average mass of an atom of an element, usually expressed in atomic mass units. The term is often used interchangeably with atomic weight.
Atomic Mass Unit One atomic mass unit (amu or u) is defined as 1/12 the mass of the standard carbon-12 isotope, or 1.66 × 10-27 kg.
Atomic Number The number of protons in an atomic nucleus.
Atomic Unit Compare with Bohr radius and hartree.A system of non-SI units used in quantum chemistry to simplify calculations and mathematical expressions. The definitions of atomic units include physical constants (like the speed of light, the rest mass of the electron, and other quantities that never change), so that all constants drop out of expressions when atomic units are used.
Atomic Weight As listed on the periodic table, the atomic weight is a weighted average of the masses of stable isotopes of an element that occur in nature. Given in grams, the atomic weight is the weight of one mole of atoms of an element. Atomic weight is often used interchangeably with atomic mass.
Attenuation/attenuate The behavior of waves as they radiate out from a source. As distance from the source increases, intensity of the waves decreases. Attenuation occurs because the same amount of energy is being spread out over a larger area.
Basalt A dark, fine-grained igneous rock formed by cooling of iron- and magnesium-rich lava above the surface of the earth. Basalt is the main component of the oceanic crust of the earth.
Base Generally, a substance that reacts with acids to form a salt, several different definitions of bases have been proposed by different scientists (listed in parentheses). 1) (Arrhenius) a compound that releases hydroxide ions (OH-) in solution; 2) (Brønsted-Lowry) a molecule or ion that accepts hydrogen ions from solution; 3) (Lewis) a molecule or ion that donates an electron pair to an acid.
Binomial A formal two word name given to each species, based on the combination of a genus name and a species name.
Biodiversity The variety and abundance of life and its ecological context, including the different kinds of organisms, the numbers of species, the variations in their genes, and the complexity of their ecological conditions.
Biogeochemical of or relating to the partitioning and cycling of chemical elements and compounds between the living and nonliving parts of an ecosystem
Biomass The combined mass of living or once-living organisms in a given area.
Biosphere The part of the world in which life can exist.
Buffer A substance that when added to solution compensates for any change in hydrogen ion concentration following the addition of an acid or a base, and thus maintains a relatively constant pH. Buffers can react with and neutralize small amounts of either acids or bases.
Buoyant Force The upward pressure exerted on an object by a fluid in which the object rests.
Calcareous Containing calcium.
Carbonic Acid The weak acid formed when CO2 dissolves in water.
Carpel (also called Pistil) Female part of a flowering plant consisting of ovary with ovules and stigma/stamen structures to receive pollen.
Cartesian Plane The Cartesian plane, named after the mathematician Rene Descartes, is a plane with a rectangular coordinate system that associates each point in the plane with a unique pair of numbers in an ordered pair of the form (x,y). The x value is the horizontal coordinate and the y value is the vertical coordinate.
Cathode A negatively charged terminal in an electrical cell.
Cathode Ray A negatively charged beam of particles (electrons) that are emitted from the negative terminal in a vacuum tube.
Cation An ion that migrates to the cathode in an electrical cell; a positively charged ion.
Chemical Bond A link between atoms. See ionic bond and covalent bond.
Chemical Reaction A process in which atoms and molecules recombine by forming or breaking chemical bonds. Chemical reactions form new products that have different chemical properties than the initial reacting material.
Classification (biological Classification) The arranging of groups of organisms into sets or divisions on the basis of their evolutionary relationships.
Combustion Commonly referred to as burning, a chemical reaction between a fuel (for example wood) and an oxidizing agent (for example oxygen) that produces heat (and usually, light).
Compound A material formed by the chemical combination of elements in defined proportions. Compounds can be chemically decomposed into simpler substances.
Conchoidal Fracture A type of breakage that produces a smooth, curved surface. Conchoidal fracture occurs when a substance has uniform strength in all directions and no pre-existing planes of atomic weakness. This generally occurs in two types of substances: minerals like quartz whose atomic structure consists of equally strong bonds in all directions, and volcanic glass, called obsidian, which has no definitive crystal structure.
Conic Section A curve formed by the intersection of a cone with a plane. This often results in a circle, ellipse or parabola. For more on conic sections, visit Mathworld's Conic Sections lesson.
Continental Crust The uppermost layer of the earth that forms the continents. Unlike oceanic crust, continental crust is created and destroyed very slowly, so there is some continental crust on the earth as old as 4 billion years. Continental crust ranges from 10-70 km thick and is composed primarily of granite.
Continental Drift The theory proposed in 1915 by Alfred Wegener, a German geophysicist and meteorologist. The theory stated that the continents had once been joined into one “supercontinent,” called Pangaea. About 200 million years ago, Pangaea broke apart and the continents drifted to their present positions. Wegener based his theory on the similarity of fossils and rock types on the east coast of South America and the west coast of Africa. The theory was widely ridiculed at the time because Wegener had not proposed a driving force for such drift.
Convection The movement or circulation of a fluid due to variations in its density as a result of the transfer of heat within the fluid.
Convergent Boundary A plate boundary where two plates are moving towards each other.
Core The innermost layer of the earth, which starts at ~2900 km depth. The core is composed mainly of iron and consists of a molten outer core and a solid inner core.
Coulomb A metric unit of electrical charge equal to the charge on 6.24 × 1018 electrons.
Covalent Bond A very strong chemical bond formed by the sharing of a pair of electrons. Multiple covalent bonds can be formed when multiple pairs of electrons are shared between atoms. Covalent bonds are generally characterized in two types, polar and non-polar covalent bonds. Compare to ionic bond, hydrogen bond.
Covalent Molecule A molecule held together by covalent bonds, that is, pairs of electrons shared between atoms. Covalent molecules are true chemical molecules whose interaction with other molecules is influenced by whether a polar molecule or non-polar molecule is formed.
Crust The uppermost 5-70 km of the earth. There are two types of crust: continental and oceanic. Continental crust ranges from 10-70 km thick and has a composition approximating that of granite. Oceanic crust, on the other hand, is approximately 5 km thick and has a composition similar to basalt, making it significantly denser than continental crust.
Crystal A solid of defined shape that is bound by plane surfaces (facets) that intersect at characteristic angles. The shape of a crystal is defined by the bonding and/or interaction between atoms, ions, or molecules that make up the solid. The substances, planar angles and defects in a crystal affect the electrical and optical properties (including color) of the crystal.
Crystallize/Crystallization The process through which crystals form, resulting in the change from a liquid or vapor to a solid. Crystallization can happen in two basic ways: 1. By lowering the temperature of a melted material like magma or water, atoms and ions start to aggregate into crystals, forming solid rock or ice. This can also happen from a vapor, as is the case with the formation of snowflakes, but it is much less common. 2. By evaporating water from a solution, the saturation point of the water is reached and a solid begins to precipitate out as crystals (for example, salt flats in the desert have been precipitated out of lakes that dried up).
Cytoplasm The internal fluid of a cell (called cytosol) along with all dissolved materials and cellular organelles except for the nucleus. The cytoplasm is the primary site for chemical activity in the cell.
Daughter A material that is derived from the breakdown or division of another. For example, a product of the radioactive decay of an element; or a cell or cells that are derived from the division of a parent cell.
Decompose To break up into constituent parts by or as if by a chemical process, to rot.
Delta Deltas form where rivers reach lakes, seas, or the ocean, and deposit their remaining sediment in a broad, flat plain as the river slows and eventually stops. The name comes from the Greek letter delta, shaped like a triangle, as these features are often triangular with one point at the river mouth.
Denitrification The loss or removal of nitrogen or nitrogen compounds; specifically: reduction of nitrates or nitrites commonly by bacteria (as in soil) that usually results in the escape of nitrogen into the air.
Density A measure of the compactness of a substance given by the mass per unit volume (d = m/v). Common units of density include g/ml, g/cm3, and kg/L. A measure of lead is not heavier than an equivalent measure of styrofoam, it is denser.
Diatomic A molecule that contains two atoms. All of the non-inert gases occur as diatomic molecules: H2, O2, N2, F2, and Cl2.
Diffract To undergo the process of diffraction.
Diffraction The bending or spreading of waves when they meet an obstruction.
Diffusion The movement of atoms or molecules from one part of a medium to another caused by their random thermal motion. The result of diffusion is a tendency for particles to move from an area of higher concentration to an area of lower concentration.
Diorite An intrusive igneous rock of intermediate composition, often called “salt-and-pepper” rock because of its speckled black and white appearance. The main minerals present are plagioclase and hornblende. Around the world, diorite forms below volcanoes along convergent boundaries, and its extrusive equivalent is andesite.
Dipole An asymmetrical distribution of electrical charge across an object. Polar molecules contain a dipole.
Dipole-dipole Interaction An interaction between two or more molecular dipoles resulting from the attraction between oppositely charged ends of the molecules.
Dissociate The breaking apart of a molecule, especially in the presence of heat or a polar solvent. For example, the ionic compound sodium chloride dissociates in water by separating into positively charged sodium ions and negatively charged chlorine atoms.
Divergent Boundary A plate boundary where two plates are moving away from each other.
DNA Deoxyribonucleic Acid. A double-stranded nucleic acid containing the sugar 2-deoxy-D-ribose. A constituent of cellular nuclear material responsible for encoding genetic information in most organisms. Specifically, a template for the synthesis of proteins and enzymes in most organisms.
Earthquake 1. The sudden motion or slip along a fault. 2. The ground shaking that results from the release of seismic energy either by (1) or by other means, such as the movement of magma beneath the surface of the earth.
Eclogite A metamorphic rock that forms from mafic rocks (like basalt and gabbro) under extremely high pressure. The main minerals present are garnet and a green pyroxene, giving the rock a characteristic, mottled red and green appearance. The most common environment where ecolgites form is deep in subduction zones, where subducted oceanic crust is put under very high pressures.
Ecosystem The complex of a community of organisms and its environment, functioning as a unit.
Electrical Charge A fundamental property used to explain attraction and repulsion between certain particles. Two types of charge exist: negative charge, which is generally conveyed as an excess of electrons; and positive charge, which is generally conveyed as a lack of electrons and excess of protons. The interaction of opposite charges produces an attractive electrical force, and the interaction of like charges produces a repulsive electrical force.
Electrical Force A fundamental force produced by the interaction of electrical charges. Sometimes called the ‘electromagnetic’ force, electrical force is several billion times stronger than gravitational force.
Electrolyte A substance that dissociates into 2 or more oppositely charged ions in water. Electrolytic solutions conduct electricity because the charged ions can carry electrons in water.
Electromagnetic Radiation A series of waves that are propagated by simultaneous, periodic variations of electrical and magnetic fields. Examples of electromagnetic radiation include radio waves, light, X-rays, gamma rays and others.
Electron A sub-atomic particle with a negative charge of 1.60 × 10-19 coulombs and a mass of 9.11 × 10-31 kg. Electrons are generally found around the nucleus of an atom, but may be gained or lost during ion formation. Compare to the proton.
Electron Shell The orbitals around the nucleus of an atom where electrons reside. Also called electron orbitals and energy levels.
Electronegativity A relative measure of the affinity (or attraction) that atoms of an element have for electrons. The higher the electronegativity of an atom, the stronger will be its affinity for electrons. The type of bond formed between two atoms (ionic or covalent) can be predicted by the difference in electronegativities of the two bonding atoms.
Element One of less than 118 pure chemical substances. An element is a substance composed of atoms with identical atomic number.
Endocytosis The uptake by a cell of material from its environment by a process in which the cell surrounds the material and engulfs it with a vesicle formed by its plasma membrane.
Endothermic A process or reaction that absorbs heat. For example, ice melting is an example of an endothermic process because it absorbs heat from its surroundings.
Energy An abstract property defined as the capacity to do work. The basic forms of energy include chemical, electrical, mechanical, nuclear and radiant (light).
Entropy A measure of disorder or randomness in a system. The 2nd law of thermodynamics states any spontaneous change is accompanied by an overall increase in entropy overall. For example, when water evaporates molecules are dispersed over greater distances resulting in an increase in entropy.
Enzyme Molecules produced by living organisms that help catalyze biochemical reactions. Enzymes are predominantly protein or protein-based molecules and are highly specific in their mechanism of action as well as the reactants that they work upon (called substrates).
Erosion The action or process of eroding: wearing away by the action of water, wind, glacial ice, etc.
Excited State An energy state for an atom in which electrons exist above the minimum or ground state configuration. In general, excited states are unstable and will quickly relax back to ground state through the emission of a quantum of energy.
Exothermic A process or reaction that releases heat. For example, wood burning in the presence of oxygen is an example of an exothermic reaction.
Extensive Property A property of matter that is dependent on the amount of material present. Common extensive properties include mass, volume, length and charge.
Extrusion A process by which viscous magma is emitted from below the surface of the earth to cool on the surface.
Floodplain The relatively flat land adjacent to a river channel that is underwater when the river floods. The floodplain is the site of deposition of sediments carried down the river and are often occupied by farms, due to the proximity of irrigation water, fertile soils, and flat topography.
Folk Taxonomy The names given to organisms and phenomena on the basis of cultural tradition as opposed to scientific study.
Force The result of an interaction that is capable of changing the state of motion of an object. A 'push or pull' on an object resulting from its interaction with another object.
Frequency The rate at which a vibration occurs that constitutes a wave, either in a material or in an electromagnetic field, usually measured in hertz (Hz).
Gabbro A dark-colored intrusive igneous rock that consists mostly of the minerals plagioclase, pyroxene, and olivine. Gabbro has a similar composition to basalt, which is extrusive. Both gabbro and basalt are mafic rocks, composed of minerals high in iron and magnesium.
Gamete Egg or sperm cell with one copy of each chromosome.
Gene Material (usually DNA) that is inherited from a parent and which encodes for a cellular component important for some cellular function.
Genotype The genetic determinants of a specific phenotype.
Genus A taxonomic category one rank or step above Species in the Linnaean system, and which may include one or many species in it.
Geosphere The part of the world in which there are rocks and minerals.
Glacial Period Any of those parts of geologic time from Precambrian onward when a much larger portion of the earth was covered by glaciers than at present.
Glossary Terms Terms highlighted in red in the main lesson text are hyperlinked to a pop-up glossary to provide easy access to definitions.
Granite A light-colored, coarse-grained igneous rock formed by cooling of silica-rich magma below the surface of the earth. Granite is considered to be the average composition of the continental crust of the earth.
Greenhouse Effect The greenhouse effect is created by gases like carbon dioxide in the earth's atmosphere. Carbon dioxide and other greenhouse gases allow radiation from the sun to pass through the atmosphere; the earth then absorbs this radiation and emits heat. That heat is absorbed by the
greenhouse gases, resulting in atmospheric warming.
Greenhouse Gas A greenhouse gas is a component of the atmosphere that absorbs heat radiated by the earth and subsequently warms the atmosphere, creating what is commonly known as the greenhouse effect. Common greenhouse gases include carbon dioxide (CO2), methane (CH4), water vapor, amd sulfate (SO4).
Ground State The lowest energy state for an atom or molecule. When an atom is in its ground state, its electrons fill the lowest energy levels before they begin to occupy higher orbitals.
Groundwater Water that fills pore space in rocks and sediments and forms a subsurface aquifer. Groundwater is distinct from soil moisture, which does not completely fill pore spaces and is immediately beneath the surface.
Half-life The time required for half of the original amount of a substance to undergo a process. For example, the time required for half of the atoms of a radioactive substance to undergo decay; or the time required for half of a ingested substance to be excreted from the body.
Heat A measure of the total internal energy of a substance that can be increased or decreased when objects with different temperatures are placed into contact. Heat is a process, not a property of a material.
Heterogeneous Mixture A mixture of two or more substances that can be easily separated by common physical means (i.e. settling, filtration, etc.). A mixture in which the components can be visibly distinguished. For example, oil and water. Compare to homogeneous mixture.
Homeothermic Of, or pertaining to, the maintenance of a uniform temperature regardless of the temperature of the surroundings. In biology, synonymous with warm-blooded.
Homogeneous Mixture A mixture of two or more substances that cannot be easily separated by common physical means (i.e. settling, filtration, etc.). A mixture with no visible separation between its components. For example, salt and water. Compare to heterogeneous mixture.
Hot Spot A fixed plume of hot magma which rises through the mantle and creates volcanoes on the earth’s surface. The Hawaiian Island chain is an example of a hot spot. Because the plumes are fixed, the hot spots record past plate motions.
Hydrocarbon An organic compound that contains only hydrogen and carbon.
Hydrogen Bond A strong dipole-dipole attraction between two or more molecules, at least one of which has a hydrogen atom bonded to an electron-withdrawing atom. More specifically, a weak bond formed between a hydrogen atom on one molecule which has developed a partial positive charge because of its bonding to an electronegative atom (commonly N, O, or F) and an electronegative atom on another molecule.
Hydrophilic Literally meaning water loving, a substance that readily associates with water. Often polar molecules or some ionic molecules that easily dissolve in or form solutions with water. Compare to hydrophobic.
Hydrophobic Literally meaning water fearing, a substance that has little affinity for water. Generally, non-polar molecules that do not dissolve in or form solutions with water. Compare to hydrophilic.
Hydroxyl An -OH group within a molecule.
Igneous Formed from the cooling and crystallization of a magma. Igneous rocks can be extrusive, meaning that they cooled on or very near the earth’s surface, or intrusive, meaning that they cooled below the earth’s surface.
Inert Deficient in active properties; especially: lacking a usual or anticipated chemical or biological action.
Intensive Property A property of matter that is independent of the amount of material present. Common intensive properties include boiling point, color, density, melting point, and solubility.
Interglacial Period Any of those parts of geologic time from Precambrian onward when a similar or lesser portion of the earth was covered by glaciers than at present.
Interstitial Pertaining to or located between the small spaces and gaps between tissues in an organism.
Ion An atom or molecule that has acquired an electrical charge by either gaining or losing electrons. A cation is an ion that has lost electrons and acquired a positive charge. An anion is an ion that has gained electrons and acquired a negative charge.
Ionic Bond A chemical bond characterized by electrostatic attraction between ions of opposite charge. The formation of an ionic bond involves a complete transfer of electrons between atoms, and can be predicted when one bonding atom has a much higher electronegativity than the other. Compare to covalent bond, hydrogen bond.
Ionic Compound A chemical compound held together by ionic bonds, that is, electrostatic attraction between positive and negative ions. Ionic compounds generally form ordered structures in which each cation is surrounded by several anions and vice versa. Thus ionic compounds commonly form complex lattices rather than true molecules.
Isomers Molecules with identical molecular formulas but differing in the sequence of bonding or arrangement in space of their atoms, i.e. their structural formulas.
Isotope Atoms of the same element with different numbers of neutrons in their atomic nucleus. Isotopes have the same chemical properties and atomic number but different atomic masses. Isotopes can differ greatly in nuclear stability.
joule A metric unit of work and energy. 1 joule (J) = 1 kg·m2/s2.
Kinetic Energy The energy an object possesses by virtue of its motion.An object of mass m moving at velocity v has a kinetic energy of ½m·v2.
Lattice A characteristic pattern formed by the spatial distribution of repeating units.
Leaching Dissolving out by the action of a percolating liquid.
Light A form of electromagnetic radiation. Visible light is that associated with stimulating the organs of sight, which for normal human vision ranges in wavelength from 3900 to 7700 ångstroms.
Limestone A sedimentary rock composed mainly of calcite (CaCO3). Limestone forms through chemical precipitation in warm, shallow seas, and often contains marine fossils.
Limiting Reactant A reactant that limits the amount of product produced in a chemical reaction.
Line Spectra An emission spectrum of light that contains very sharply defined lines. Line spectra are given off when matter is heated or excited in some way and each line corresponds to a wavelength of light given off during an electron transition from an excited state to the ground state.
Linnaean Hierarchy The seven major categories of biological classification based on Linnaeus’ system: Kingdom, Phylum, Class, Order, Family, Genus, and Species.
Lipids A diverse group of organic molecules that contain long hydrocarbon chains or rings and are hydrophobic. Examples are fats, oils, waxes, and steroids.
Lithosphere The rigid upper layer of the earth consisting of the crust and the upper mantle. The earth’s tectonic plates are composed of pieces of the lithosphere. The lithosphere ranges in thickness from 10-12 km underneath the oceans to 70-200 km at the continents.
Magma Molten rock below the surface of the earth.
Mantle The middle portion of the interior of the earth, starting below the crust at 5-70 km below the earth’s surface and continuing to a depth of 2900 km. The mantle is composed mainly of the rock peridotite.
Mass a fundamental property of matter which is a numerical measure of the inertia of an object or the amount of matter that an object contains. The mass of an object is different from its weight as mass is independent of the gravitational field exerted on an object.
Mass Spectrometer A spectrometer that measures the composition of samples by analyzing the mass to charge ratio (m/z) of components in the sample. To do this, the sample introduced into the spectrometer is ionized under high energy, and the various ions are then seperated in a magnetic field and measured. The specific m/z signature of each ion is then used to identify the parent element or compound. For additional information, see the Wikipedia's definition of mass spectrometry.
Mesosphere 1. The lowermost portion of the mantle. 2. The layer of the atmosphere above the stratosphere, where temperature decreases with altitude.
Metabolism A sequence of biochemical reactions in living organisms that converts food into energy used to drive other biological processes. Also, the sequence of transformations foreign compounds undergo inside a living cell.
Metamorphic Formed through the processes involved in metamorphism, which include deep burial, exposure to high temperatures and pressures, and interactions with hydrothermal fluids. Metamorphic rocks are generally considered to have a parent rock, or protolith, which can be any rock type. The minerals and textures that are produced through metamorphism are indicative of both the protolith and the metamorphic environment.
Metamorphism Physical and chemical