Glossary
Amber: A fossil created from tree resin. Yellow or brown in color and transparent, sometimes containing ancient trapped insects.
Appalachian Plateau province: The geologic region of far western Virginia containing most of the state’s coal and natural gas. Made of mostly flat layers of sedimentary rocks with deep canyons, such as the one found in the Breaks Interstate Park measuring more than 5 miles long and 1600 feet deep.
Basalt: A dark, very fine-grained igneous rock formed by cooling lava. Basalt is generally found in the Blue Ridge province of Virginia. Small pieces of basalt called cinders can be spread on icy roads to increase traction in the winter.
Bedrock: The solid rock below the soil, gravel, or other material at the Earth’s surface.
Blue Ridge province: The long mountain chain that is a part of the Appalachian Mountains in western Virginia. Made of folded and faulted igneous and metamorphic rocks. Mount Rogers, the highest point in the state, is found in this region.
Clay: An earthy, mud-like sediment composed of very fine particles of minerals. Pliable when moist, but becomes hard when dry or fired. Commonly used to make brick, tile, and pottery. Generally found in the Piedmont and Coastal Plain provinces of Virginia.
Cleavage: The tendency of a mineral to break along defined planes determined by the mineral’s crystal structure. Also, the tendency of a rock to break along parallel, closely-spaced planes.
Coal: A black, combustible rock made of carbon. Formed after decomposed plant matter is subjected to extreme, prolonged pressure without access to air. Commonly used as a heating fuel. Found in the Appalachian Plateau province of Virginia.
Coastal Plain province: The broad, flat, eastern part of Virginia composed of thousands of layers of sand, clay, and other sediments. Formed by rivers and the ocean laying down sediments for more than a hundred million years. At one time, part of the Coastal Plain was the sea floor of the Atlantic Ocean.
Conglomerate: A coarse-grained sedimentary rock composed of a mass of rounded stones ranging from small pebbles to large boulders, in a matrix of finer grains such as sand or clay. Can be found in the Appalachian Plateau province of Virginia.
Core: The hot central part of the Earth, made of iron and nickel. Has a radius of about 2100 miles, and begins at about 1800 miles underground.
Crust: The outermost layer of the Earth, consisting mostly of crystalline rocks and making up less than 1% of the Earth’s total volume.
Crystal: A homogeneous solid that has a regularly repeating internal arrangement of its atoms and has external plane faces.
Deposition: The laying down or depositing of rock-forming materials by natural processes, such as the settling of sediment in a river.
Diabase: A dark, fine-grained igneous rock, consisting mainly of dark pyroxene surrounding light feldspar crystals. Generally found in the Piedmont province of Virginia and sometimes polished and used as a building stone.
Earthquake: A sudden shaking or trembling of the Earth that is volcanic or tectonic in origin.
Erosion: The wearing away of soil and rock. Natural forces such as weathering, glaciers, ocean waves, and underground water are responsible for most long-term erosion. Man-made forces such as pollution, chemicals, and land clearing are modern-day causes of erosion.
Fault: A fracture in the Earth’s crust, along which movement has occurred. The rocks on one side of a fault have moved with respect to those on the other side.
Feldspar: A group of rock-forming, igneous minerals that make up 60% of the Earth’s crust. Feldspar colors range from white and gray to pink. Pink and white feldspars are mainly found in Virginia’s Piedmont province. Commonly used in the ceramic industry for making glazes.
Fold: A bend or warping in rock, usually produced by forces after the deposition and consolidation of the rock.
Fossil: Any remnant, trace, or imprint of a plant, insect, or animal naturally buried and preserved in rocks or sediments from a past geologic time.
Garnet: A mineral commonly found in metamorphic rocks such as gneiss and schist. Typically looks like chunks of dark red glass. Used as a semiprecious stone and as an abrasive.
Geology: The scientific study of the planet Earth, including its history as recorded in rocks. Also known as earth sciences.
Geologist: A person who is trained in and works in the field of geology or earth sciences.
Glacier: A large mass of ice moving slowly down a slope or valley or spreading outward across land.
Grain: A mineral or rock particle measuring less than a few millimeters across, such as sand. The grain of an area can also mean the linear arrangement of topographic features in a region, such as parallel ridges or valleys.
Granite: A very hard, durable, light-colored igneous rock comprised mainly of quartz and feldspar. Widely used in building construction, as steps, and as kitchen countertops, among many other uses. Found in the Piedmont province of Virginia.
Graphite: A soft, black, lustrous mineral made of carbon. Easily conducts electricity. Used in lead pencils, paints, crucibles, and as a lubricant.
Greenstone: A term used to describe any compact, dark green, basic metamorphic rock. Common in the Blue Ridge province of Virginia.
Hardness: The comparative resistance of a mineral to scratching. The Mohs scale is commonly used to describe a mineral’s hardness, with a rating of 1 to 10 (softest to hardest).
Igneous rock: A rock or mineral that has crystallized from molten material, such as from a lava flow or from the magma below the Earth’s surface. This is one of three classifications of rocks; the other two are sedimentary and metamorphic. Virtually all of Virginia’s igneous rock is found in the Piedmont and Blue Ridge provinces.
Lava: Molten rock that has flowed out of the Earth through a volcano or fissure. The term \"lava rock\" is sometimes used to describe formerly molten lava that has solidified by cooling.
Limestone: A sedimentary rock consisting mainly of the mineral calcite (calcium carbonate). Used extensively in construction materials such as cement. Found in Virginia’s Piedmont province.
Luster: The quality and intensity of light reflected from the surface of a mineral.
Magma: Hot, melted rock inside the Earth. Forms igneous rock when it cools.
Mantle: The region of melted rock inside the Earth that is below the crust and above the core. Divided into two parts, the upper mantle and the lower mantle.
Marble: A metamorphic rock consisting of calcite, created when limestone is metamorphosed. Can be polished and used for a wide range of architectural uses from the exterior of buildings to fireplace mantels. Found in the Piedmont province of Virginia.
Metamorphic rock: A rock that has been altered physically, chemically, and mineralogically in response to strong changes in temperature, pressure, shearing stress, and underground water. Metamorphic rocks are found in the Piedmont and Blue Ridge provinces of Virginia.
Mica: A group of minerals with a sheet-like crystal structure that easily separate into thin, transparent leaves. Micas can be found in the igneous and metamorphic rocks of the Piedmont and Blue Ridge provinces of Virginia.
Mineral: A naturally occurring, homogeneous, usually inorganic, solid substance with a definite chemical composition and characteristic crystal structure, hardness, and color. Some examples of minerals are mica, feldspar, quartz, and salt.
Organic matter: Any substance or compound containing carbon as an essential component. Organic sedimentary rocks, such as coal, are chiefly composed of the remains of carbon-based plants or animals.
Pangaea: A supercontinent existing about 200 to 300 million years ago that included most of the world’s land mass. Geologists believe that today’s continents were formed by the splitting apart of this supercontinent.
Petrified wood: Wood that has been fossilized and converted into rock. Water containing the components of minerals such as quartz and calcite infiltrates the wood and, over time, replaces the organic material in the wood. The resulting petrified wood is made of rock but still has the appearance of wood.
Piedmont province: One of the five physiological provinces of Virginia (the others are the Appalachian Plateau, Valley and Ridge, Blue Ridge, and Coastal Plain). Located in the central part of the state, the Piedmont province has a bedrock of folded and faulted metamorphic and igneous rocks. The only sedimentary rocks found in this area are located in its Triassic basins. Diabase, granite, gneiss, marble, and schist are among the rocks found in the Piedmont province.
Plates: Large, thin, rigid sections of the Earth’s crust that cover the entire surface of the planet and fit together like puzzle-pieces. Zones of volcanic and seismic activity are found where one plate meets another.
Plate tectonics: The concept that the Earth’s surface is divided into a number of interconnected, large plates made of rock. These plates move very slowly over time, causing earthquakes and creating volcanoes, mountains, and valleys, depending on the direction of their movement.
Pressure: A force that is applied uniformly to a surface, measured as force per unit of area.
Pyrite: A common mineral consisting of iron disulfide that is often mistaken for gold (and called \"fool’s gold\") due to its bright, yellow, metallic luster. Used to make chemicals such as sulfur dioxide and sulfuric acid.
Quartz: Next to feldspar, quartz is the most common mineral. It can be found in igneous, sedimentary, and metamorphic rocks. Quartz is made of crystalline silica, can be transparent or opaque, and can be nearly any color but is most often white, gray, pink, or light brown. Found in all five provinces of Virginia.
Rock: An aggregate of one or more minerals, or a concentrated mass of stony material. Examples of rocks are granite, shale, marble, or conglomerate.
Sandstone: A sedimentary rock consisting of sand grains (often made of quartz), bounded together by silica, iron oxide, or calcite. Found in the Valley and Ridge province of Virginia.
Sedimentary rock: A layered rock formed by the consolidation of sediment. Sedimentary rocks are created as rock fragments are transported from their source and deposited elsewhere by water. Much of Virginia’s sedimentary rock is found in the Valley and Ridge province.
Sediment: Unconsolidated, loose, solid material such as pebbles, sand, or clay. Wind, water, or ice can transport these particles from their source and deposit them in rivers, lakes, or oceans.
Shale: A fine-grained sedimentary rock formed by the compaction of clay or mud. Characterized by a fine, layered structure allowing this rock to split easily along these layers. Some shales contain oil and can be mined for petroleum. Shale is found in the Valley and Ridge province of Virginia.
Silica: Silicon dioxide, which entirely composes the mineral quartz, and is a major component of many minerals, like feldspar and mica.
Sinkhole: A depression at the Earth’s surface caused by the underlying rock dissolving or collapsing. Partially dissolved masses of underground limestone often result in sinkholes and caverns.
Slate: Shale that has been metamorphosed, resulting in a dense, fine-grained metamorphic rock. The compression of sediments during metamorphism results in cleavage, allowing slate to split into slabs and thin plates. This property makes slate useful in architectural applications, such as walkways and roof shingles, as well as for pool tables and blackboards. Found in Virginia’s Piedmont province.
Soapstone: A soft metamorphic rock made up essentially of the mineral talc and having a \"soapy\" feel. Used for walkways, building stone, wood stoves, and sculptures. Found in Virginia’s Piedmont province.
Specific gravity: The ratio of the weight of a given volume of material to the weight of the same volume of water.
Streak: The color of a mineral when it is ground into a fine powder. This color is obtained by rubbing the mineral across a hard white surface (such as a streak plate) and observing the mark it leaves.
Subduction: The process of the edge of one crustal plate descending beneath the edge of another.
Valley and Ridge province: This region is located in the western part of Virginia and is characterized by its long, parallel valleys and ridges. It is made of folded and faulted sedimentary rocks. The Valley and Ridge contains large deposits of limestone, and most of the state’s caverns and sinkholes are located here.
Volcano: A vent in the surface of the Earth through which gases, ash, and molten rock erupt.
Weathering: The physical breakdown of rocks from exposure to the elements of rain, wind, and ice.
