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  1. The development of new crystals in a rock, often of the same composition as the original grains.
  2. A moving body of water, confined in a channel and running downhill under the influence of gravity.
  3. Describing a substance in which the atoms are arranged in a regular, repeating, orderly pattern.
  4. Silicate minerals that are structured so that none of the oxygen atoms are shared by silica tetrahedrons.
  5. For igneous rocks, refers to the size of mineral crystals in the rock.
  6. Group of minerals with a sheet silicate structure.
  7. Point of land along a coast.
  8. The grinding away of rock by friction and impact during transportation. (Begin Chapter 10)
  9. A drainage pattern in which tributaries of a river change direction and join one another at right angles.
  10. Low ridges of flood-deposited sediment formed on either side of a stream channel, which thin away from the channel.
  11. The total amount of a geologic material in all its deposits, discovered and undiscovered (see reserves).
  12. There is no definition for this term in the glossary.
  13. A measure of an earthquake's size by its effect on people and buildings.
  14. Dripstone deposit of calcite that precipitate from dripping water in caves.
  15. The ability of water to pick up and move rock and sediment.
  16. Naturally occurring material that can be profitably mined.
  17. of rock distinct from the igneous rock in which it is enclosed. (End Chapter 3)
  18. Soil not formed from the local rock but from parent material brought in from some other region and deposited, usually by running water, wind, or glacial ice.
  19. Mineral group, all members of which are single chain silicates.
  20. V-shaped valleys that run across the continental shelf and down the continental slope.
  21. A frothy volcanic glass.
  22. A type of frost action in which the expansion of freezing water pries a rock apart.
  23. Any rock that was older than and intruded by an igneous body.
  24. A concept suggesting that continents move over Earth's surface.
  25. A large, long-lasting mass of ice, formed on land by the compaction and recrystallization of snow, which moves because of its own weight.
  26. A tensional valley bounded by normal faults. Rift valleys are found at diverging plate boundaries on continents and along the crest of the mid-oceanic ridge.
  27. Heavy or large sediment particles in a stream that travel near or on the stream bed.
  28. Silicate structure in which two of each tetrahedron's oxygen ions are shared with adjacent tetrahedrons, resulting in a chain of tetrahedrons.
  29. That portion of a glacier in which ice is lost.
  30. The boundary separating the crust from the mantle beneath it (also called Moho),.
  31. In mass wasting, movement of a relatively coherent descending mass along one or more well-defined surfaces.
  32. Rapid sliding of a mass of bedrock along an inclined surface of weakness.
  33. Bend in layered bedrock.
  34. A body of intrusive rock classified on the basis of size, shape, and relationship to surrounding rocks.
  35. Rock with a chemical content between felsic and mafic compositions.
  36. A stream bar (see definition) deposited on the inside of a curve in the stream, where the water velocity is low.
  37. The lifting of rock or soil by the expansion of freezing water.
  38. Two thin layers of sediment, one dark and the other light in color, representing one year's deposition in a lake.
  39. Boundary separating two plates moving away from each other.
  40. Any unconsolidated material at Earth's surface.
  41. A force acting on a body, or rock unit, that tends to change the size or shape of that body, or rock unit. Force per unit area within a body.
  42. A small rock island that is an erosional remnant of a headland left behind as a wave-eroded coast retreats inland.
  43. The youngest geologic period; includes the present time.
  44. The sliding of the sea floor beneath a continent or island arc.
  45. A fine-grained, felsic, igneous rock made up mostly of feldspar and quartz.
  46. Rock that appears to have crystallized from magma emplaced in surrounding rock.
  47. An area where the strength of the magnetic field is greatest and where the magnetic lines of force appear to leave or enter Earth.
  48. A region of Earth's outer shell beneath the lithosphere. The asthenosphere is of indeterminate thickness and behaves plastically. (Begin Chapter 1)
  49. Layers of basalt flows that have built up to great thicknesses.
  50. A major concentration of earthquakes and composite volcanoes that runs through the Mediterranean Sea, crosses the Mideast and the Himalaya, and passes through the East Indies.
  51. A reverse fault in which the dip of the fault plane is at a low angle to horizontal. (End Chapter 15)
  52. A body of sediment deposited at the mouth of a river when the river velocity decreases as it flows into a standing body of water.
  53. A mine in which the valuable material is exposed at the surface by removing a strip of overburden.
  54. The land near the sea, including the beach and a strip of land inland from the beach.
  55. A region on the downwind side of mountains that has little or no rain because of the loss of moisture on the upwind side of the mountains.
  56. Greater than normal gravitational attraction.
  57. Movement within a glacier in which the ice is not fractured.
  58. Dense, viscous petroleum that flows slowly or not at all.
  59. A stream that receives water from the zone of saturation.
  60. In an intrusion, the finer-grained rock adjacent to a contact with country rock.
  61. A rock that is sufficiently porous and permeable to store and transmit petroleum.
  62. Unsorted and unlayered rock debris carried by a glacier.
  63. The detachment of part of the mantle portion of the lithosphere beneath a mountain belt.
  64. Describing a rock that splits easily along nearly flat and parallel planes.
  65. Large spindle- or lens-shaped pyroclast.
  66. In mass wasting, movement along a curved surface in which the upper part moves vertically downward while the lower part moves outward. Also called a slump.
  67. Age given in years or some other unit of time.
  68. Rock falling freely or bouncing down a cliff.
  69. Asphalt-cemented sand deposit.
  70. A seismic wave that travels on Earth's surface.
  71. A hill or mountain constructed by the extrusion of lava or rock fragments from a vent. (End Chapter 4)
  72. A gently sloping erosional surface cut into the solid rock of a mountain range in a dry region; usually covered with a thin veneer of gravel.
  73. A long, streamlined hill made of till.
  74. Distinct earthquake zone that begins at an oceanic trench and slopes landward and downward into Earth at an angle of about 30° to 60°.
  75. A curved line of islands.
  76. The grinding away of sharp edges and corners of rock fragments during transportation.
  77. Material is in equilibrium if it is adjusted to the physical and chemical conditions of its environment so that it does not change or alter with time.
  78. A relatively straight, elongate dune oriented perpendicular to the wind.
  79. The portion of a fracture zone between two offset segments of a mid oceanic ridge crest.
  80. Portion of a continent that has been structurally stable for a prolonged period of time.
  81. Very rapid and turbulent mass wasting of debris, air, and water.
  82. An irregular line marking the highest level to which the winter snow cover on a glacier is lost during a melt season. (Also called snow line.)
  83. Change in size (volume) or shape of a body (or rock unit) in response to stress.
  84. Arrangement of various faces on a crystal in a definite geometric relationship to one another.
  85. A seismometer with a recording device that produces a permanent record of Earth motion.
  86. A significant type of mechanical weathering that causes rocks to crack when overburden is removed.
  87. Distance between the focus and the epicenter of an earthquake.
  88. Boulder, cobble, or pebble with flat surfaces caused by the abrasion of wind-blown sand. (End Chapter 13)
  89. The point on Earth's surface directly above the focus of an earthquake.
  90. Varying rates of weathering resulting from some rocks in an area being more resistant to weathering than others.
  91. A sharp ridge that separates adjacent glacially carved valleys.
  92. An area with many sinkholes and a cave system beneath the land surface and usually lacking a surface stream.
  93. Surface mines in which valuable mineral grains are extracted from stream bar or beach deposits.
  94. A cavity in volcanic rock caused by gas in a lava.
  95. In a stream, the volume of water that flows past a given point in a unit of time.
  96. A type of surface seismic wave that behaves like a rolling ocean wave and causes the ground to move in an elliptical path.
  97. Capable of being molded and bent under stress.
  98. Drowned river mouth.
  99. A term used for oxygen plus silicon.
  100. A metamorphic rock composed of light and dark layers or lenses.
  101. Water flowing down a slope in a layer.
  102. A liquid mixture of naturally occurring hydrocarbons.
  103. A water table separated from the main water table beneath it by a zone that is not saturated.
  104. A ridge of sediment that cuts a bay off from the ocean.
  105. See rock-basin lake.
  106. An arrangement of interlocking crystals.
  107. A fine-grained, mafic, igneous rock composed predominantly of ferromagnesian minerals and with lesser amounts of calcium-rich plagioclase feldspar.
  108. Resistance to flow.
  109. Large fan-shaped pile of sediment that usually forms where a stream's velocity decreases as it emerges from a narrow canyon onto a flat plain at the foot of a mountain range.
  110. A principle or law stating that within a sequence of undisturbed sedimentary rocks, the oldest layers are on the bottom, the youngest on the top.
  111. Erosion and undercutting of stream banks caused by a stream swinging from side to side across its valley floor.
  112. The top layer of soil, characterized by the downward movement of water; also called zone of leaching. (Begin Chapter 5)
  113. Observations or measurements used by scientists to test hypotheses.
  114. Less than average strength of Earth's magnetic field.
  115. The maximum amount of stress that can be applied to a body before it deforms in a permanent way by bending or breaking.
  116. Narrow column of hot mantle rock that rises and spreads radially outward.
  117. A set of conditions that hold petroleum in a reservoir rock and prevent its escape by migration.
  118. A moving mass of water that develops parallel to a shoreline.
  119. In mass wasting, the resistance to movement or deformation of material.
  120. Sediment in a stream that is light enough in weight to remain lifted indefinitely above the bottom by water turbulence.
  121. Transparent or white mica that lacks iron and magnesium.
  122. Movement, caused by gravity, in which bedrock, rock debris, or soil moves downslope in bulk.
  123. A rock produced by metamorphism.
  124. A surface that represents missing rock strata but beds above and below that surface are parallel to one another.
  125. iron oxide that is attracted to a magnet.
  126. A type of movement that implies that a descending mass is moving downslope as a viscous fluid.
  127. The application of physical laws and principles to a study of Earth.
  128. Rate of temperature increase associated with increasing depth beneath the surface of Earth (normally about 25°C/km).
  129. A place where water flows naturally out of rock onto the land surface.
  130. An unconformity in which younger strata overlie an erosion surface on tilted or folded layered rock. (Begin Chapter 8)
  131. A glacier covering a large area (more than 50,000 square kilometers) of land.
  132. Mineral with the formula CaCO3.
  133. A margin consisting of a continental shelf, a continental slope, and an oceanic trench.
  134. Volcanic activity, including the eruption of lava and rock fragments and gas explosions.
  135. A trembling or shaking of the ground caused by the sudden release of energy stored in the rocks beneath the surface.
  136. Fine-grained igneous rock of intermediate composition. Up to half of the rock is plagioclase feldspar with the rest being ferromagnesian minerals. (Begin Chapter 3)
  137. The texture of a metamorphic rock in which minerals are separated into light and dark layers or lenses.
  138. A substance that contains silica as part of its chemical formula.
  139. Soil that develops directly from weathering of the rock below.
  140. Submarine ridge with which no earthquakes are associated.
  141. A margin that includes a continental shelf, continental slope, and continental rise that generally extends down to an abyssal plain at a depth of about 5 kilometers.
  142. Fragment of rock formed by volcanic explosion.
  143. A large, mobile slab of rock making up part of Earth's surface.
  144. A fine-grained rock that splits easily along flat, parallel planes.
  145. A luster giving a substance the appearance of unglazed pottery.
  146. An arched fold in which the rock layers usually dip away from the axis of the fold.
  147. The sudden release of progressively stored strain in rocks results in movement along a fault.
  148. A depression of the water table formed around a well when water is pumped out; it is shaped like an inverted cone.
  149. The physical removal of rock by an agent such as running water, glacial ice, or wind.
  150. The chemical precipitation of material in the spaces between sediment grains, binding the grains together into a hard rock.
  151. A submarine platform at the edge of a continent, inclined very gently seaward generally at an angle of less than 1°.
  152. A sedimentary rock composed mostly of calcite.
  153. A broad, gently sloping, depositional surface formed at the base of a mountain range in a dry region by the coalescing of individual alluvial fans. (Begin Chapter 13)
  154. A feature found within sedimentary rocks, usually formed during or shortly after deposition of the sediment and before lithification.
  155. Separation of different ingredients from an originally homogeneous mixture.
  156. Mixed igneous and metamorphic rock.
  157. Principle that geologic processes operating at present are the same processes that operated in the past. The principle is stated more succinctly as "The present is the key to the past." Also, see actualism. (End Chapter 8)
  158. A long, narrow depression, shaped and more or less filled by a stream.
  159. The compass direction of a line formed by the intersection of an inclined plane (such as a bedding plane) with a horizontal plane.
  160. A feldspar containing sodium and/or calcium in addition to aluminum, silicon, and oxygen.
  161. A fracture or crack in bedrock along which essentially no displacement has occurred.
  162. Metamorphic rocks that contain the same set of pressure or temperature sensitive minerals are regarded as belonging to the same facies, implying that they formed under broadly similar pressure and temperature conditions.
  163. The covering of a large region of a continent by a sheet of glacial ice.
  164. Line about which a fold appears to be hinged. Line of maximum curvature of a folded surface.
  165. A fine-grained deposit of wind-blown dust.
  166. The texture of a rock in which visible platy or needle-shaped minerals have grown essentially parallel to each other under the influence of directed pressure.
  167. A crescent-shaped lake occupying the abandoned channel of a stream meander that is isolated from the present channel by a meander cutoff and sedimentation.
  168. An accumulation of broken rock at the base of a cliff. (End Chapter 9)
  169. Steep slope that retreats inland by mass wasting as wave erosion undercuts it.
  170. A mafic, coarse-grained igneous rock composed predominantly of ferromagnesian minerals and with lesser amounts of calcium-rich plagioclase feldspar.
  171. A wave of energy produced by an earthquake.
  172. The most recent of the eras; followed the Mesozoic Era.
  173. Boundary between two plates that are sliding past each other.
  174. Capable of being molded and bent under stress.
  175. A fingerlike ridge of sediment attached to land but extending out into open water.
  176. Silica-rich igneous rock or magma with a relatively high content of potassium and sodium.
  177. Fine-grained igneous rock of intermediate composition. Up to half of the rock is plagioclase feldspar with the rest being ferromagnesian minerals. (Begin Chapter 4)
  178. The general term for a slowly to very rapidly descending mass of rock or debris.
  179. A volcanic depression much larger than the original crater.
  180. A glacier covering a relatively small area of land but not restricted to a valley.
  181. Any of the layers of soil that are distinguishable by characteristic physical or chemical properties.
  182. An instrument that measures the strength of Earth's magnetic field.
  183. A numerical scale of earthquake magnitudes.
  184. The lengthening of a valley in an uphill direction above its original source by gullying, mass wasting, and sheet erosion.
  185. A map representing the geology of a given area.
  186. A wave that has become so steep that the crest of the wave topples forward, moving faster than the main body of the wave.
  187. A stress due to a force pulling away on a body.
  188. A major concentration of earthquakes and composite volcanoes that runs through the Mediterranean Sea, crosses the Mideast and the Himalaya, and passes through the East Indies.
  189. A change in Earth's magnetic field b,etween normal polarity and reversed polarity. In normal polarity the north magnetic pole, where magnetic lines of force enter Earth, lies near the geographic North Pole. In reversed polarity the south magnetic pole, where lines of force leave Earth, lies near the geographic North Pole (the magnetic poles have exchanged positions).
  190. The consolidation of sediment into sedimentary rock.
  191. That portion of a glacier with a perennial snow cover. (End of Chapter 12)
  192. Metamorphism that takes place at considerable depth underground.
  193. A luster that gives a substance a glazed, porcelainlike appearance.
  194. A free-falling mass of debris.
  195. The total number of neutrons and protons in an atom.
  196. The portion of the total sediment load in a stream that is carried in solution.
  197. A region with low precipitation (usually defined as less than 25 cm per year).
  198. Igneous rock formed at great depth.
  199. The horizontal distance between two wave crests (or two troughs).
  200. Total area drained by a stream and its tributaries.
  201. Mine in which ore is exposed at the surface in a large excavation.
  202. A bottom current that flows parallel to the slopes of the continental margin (along the contour rather than down the slope).
  203. A steep-sided, dome- or spine-shaped mass of volcanic rock formed from viscous lava that solidifies in or immediately above a volcanic vent.
  204. A thick shell of rock that separates Earth's crust above from the core below.
  205. A fold with gently dipping limbs.
  206. A fault in which movement is parallel to the dip of the fault surface.
  207. Rapid movement of debris as a coherent mass.
  208. Partly hollow, globelike body found in limestone or other cavernous rock.
  209. hardness scale Scale on which ten minerals are designated as standards of hardness.
  210. Flat-topped seamount.
  211. A rock formed from fine-grained pyroclastic particles (ash and dust).
  212. A mound of loose sand grains heaped up by the wind.
  213. Four-sided, pyramidal object that visually represents the four oxygen atoms surrounding a silicon atom; the basic building block of silicate minerals. Also called a silica tetrahedron or a silicon tetrahedron.
  214. Cracking or rupturing of a body under stress.
  215. The sum of the weight of the subatomic particles in an average atom of an element, given in atomic mass units.
  216. Platform of wave-deposited sediment that is flat or slopes slightly landward.
  217. A large discordant pluton with an outcropping area greater than 100 square kilometers.
  218. A body of rock of considerable thickness that has a recognizable unity or similarity making it distinguishable from adjacent rock units. Usually composed of one bed or several beds of sedimentary rock, although the term is also applied to units of metamorphic and igneous rock. A convenient unit for mapping, describing, or interpreting the geology of a region.
  219. Volcanic rock in parallel, usually vertical columns, mostly six-sided; also called columnar jointing.
  220. The quality and intensity of light reflected from the surface of a mineral.
  221. A closed depression found on land surfaces underlain by limestone.
  222. Bridge of rock left above an opening eroded in a headland by waves. (Begin Chapter 14)
  223. An instrument that measures the gravitational attraction between Earth and a mass within the instrument.
  224. Strip of sediment, usually sand but sometimes pebbles, boulders, or mud, that extends from the low-water line inland to a cliff or zone of permanent vegetation.
  225. The group of processes that change rock at or near Earth's surface. (End Chapter 5)
  226. The opening in Earth's surface through which a volcanic eruption takes place.
  227. The discovered deposits of a geologic material that are economically and legally feasible to recover under present circumstances.
  228. A metamorphic rock in which clay minerals have recrystallized into microscopic micas, giving the rock a silky sheen.
  229. Movement in which parts of a body slide relative to one another and parallel to the forces being exerted.
  230. A medium-grained sedimentary rock (grains between 1/16 mm and 2 mm) formed by the cementation of sand grains.
  231. Soil containing approximately equal amounts of sand, silt, and clay.
  232. Joints oriented in one direction approximately parallel to one another.
  233. A horizontal bench of rock formed beneath the surf zone as a coast retreats because of wave erosion.
  234. The stripping of concentric rock slabs from the outer surface of a rock mass.
  235. Usually slow but effective process of weathering and erosion in which rocks are dissolved by water.
  236. An eruption in which lava erupts out of a vent on the side of a volcano.
  237. A stream that flows in a network of many interconnected rivulets around numerous bars.
  238. A coarse-grained rock composed of interlocking calcite (or dolomite) crystals.
  239. A fine-grained, unfoliated metamorphic rock.
  240. The arrangement in map view of a river and its tributaries.
  241. Flow of water saturated debris over impermeable material.
  242. A blanket of till deposited by a glacier or released as glacier ice melted.
  243. The removal of clay, silt, and sand particles from the land surface by wind.
  244. Movement in which the entire glacier slides along as a single body on its base over the underlying rock.
  245. In mass wasting, the component of gravitational force that is parallel to an inclined surface.
  246. Drainage pattern of a river and its tributaries, which resembles the branches of a tree or veins in a leaf.
  247. Narrow currents that flow straight out to sea in the surf zone, returning water seaward that has been pushed ashore by breaking waves.
  248. Attachment of an atom to one or more adjacent atoms.
  249. Molten rock, usually mostly silica. The liquid may contain dissolved gases as well as some solid minerals.
  250. The percentage of a rock's volume that is taken up by openings.
  251. A fragment of rock that is distinct from the body of igneous rock in which it is enclosed.
  252. The low point of a wave.
  253. Broad, gently sloping cone constructed of solidified lava flows.
  254. Rock that has formed from (1) lithification of any type of sediment, (2) precipitation from solution, or (3) consolidation of the remains of plants or animals.
  255. Eon of Precambrian time.
  256. Boundary between two plates that are sliding past each other. (End Chapter 1)
  257. A principle or law stating that a disrupted pattern is older than the cause of disruption.
  258. The largest unit of geological time.
  259. The time it takes for a given amount of a radioactive isotope to be reduced by one-half.
  260. A fault with both strike-slip and dip-slip components.
  261. A broad, gently sloping platform that may be exposed at low tide.
  262. Concept of vertical movement of sections of Earth's crust to achieve balance or equilibrium.
  263. Glaciation of a mountainous area.
  264. An ultramafic rock composed primarily of the mineral olivine.
  265. A metamorphic rock characterized by coarse-grained minerals oriented approximately parallel.
  266. Characteristic cross-profile of a valley carved by glacial erosion.
  267. Small earthquake that follows a main shock. (Begin Chapter 16)
  268. A vertical angle measured downward from the horizontal plane to an inclined plane. (Begin Chapter 15)
  269. Crystal structure in which each silica tetrahedron shares three oxygen ions.
  270. The movement of water and water vapor from the sea to the atmosphere, to the land, and back to the sea and atmosphere again.
  271. The total amount of space taken up by openings between sediment grains.
  272. A steep-sided, amphitheater-like hollow carved into a mountain at the head of a glacial valley.
  273. Forces generated from within Earth that result in uplift, movement, or deformation of part of Earth's crust.
  274. A region of Earth's outer shell beneath the lithosphere. The asthenosphere is of indeterminate thickness and behaves plastically.
  275. A distinctive rock sequence found in many mountain ranges on continents.
  276. A deeply curved dune in a region of abundant sand. The horns point upwind and are often anchored by vegetation.
  277. Luster giving a substance the appearance of being made of metal.
  278. A powder of fine fragments of rock produced by glacial abrasion.
  279. The physical disintegration of rock into smaller pieces.
  280. The deposition of most water-laid sediment in horizontal or near-horizontal layers that are essentially parallel to Earth's surface.
  281. Polygonal crack formed in very fine grained sediment as it dries.
  282. Rocks, generally basalt, formed in pillow shaped masses fitting closely together; caused by underwater lava flows.
  283. Rock composed mostly of the remains of plants and animals.
  284. Silica-deficient igneous rock with a relatively high content of magnesium, iron, and calcium.
  285. The high point of a wave.
  286. The return of part of the energy of seismic waves to Earth's surface after the waves bounce off a rock boundary.
  287. The ability of a mineral to break along preferred planes.
  288. A very slow circulation of a substance driven by differences in temperature and density within that substance.
  289. and interrelationships of rock units.
  290. The spontaneous nuclear disintegration of certain isotopes.
  291. A naturally occurring, crystalline solid that has a specific chemical composition.
  292. A wedge of sediment that extends from the lower part of the continental slope to the deep sea floor.
  293. Bonding due to the attraction between positively charged ions and negatively charged ions.
  294. A soil layer characterized by the accumulation of material leached downward from the A horizon above; also called zone of accumulation.
  295. A rock composed of sand-sized grains of quartz that have been welded together during metamorphism.
  296. A well in which water rises above the aquifer.
  297. A study of ancient magnetic fields.
  298. An intrusive structure that apparently represents magma that solidified within the throat of a volcano.
  299. A terrane that may not have formed at its present site.
  300. A flowing mass of sediment-laden water that is heavier than clear water and therefore flows downslope along the bottom of the sea or a lake.
  301. The loss of the glacial ice or snow by melting, evaporation, or breaking off into icebergs. (Also called wastage). (Begin Chapter 12)
  302. Valuable materials of geologic origin that can be extracted from Earth.
  303. A mode of transport that carries sediment downcurrent in a series of short leaps or bounces.
  304. An arrangement of relatively thin layers of rock inclined at an angle to the more nearly horizontal bedding planes of the larger rock unit.
  305. The ratio of the mass of a substance to the mass of an equal volume of water, determined at a specified temperature.
  306. The present epoch of the Quaternary Period.
  307. Seismic wave that travels through Earth's interior.
  308. Lithified till.
  309. Iron/magnesium bearing mica.
  310. Collective term for several clay minerals.
  311. The concept that the ocean floor is moving away from the mid oceanic ridge and across the deep ocean basin, to disappear beneath continents and island arcs.
  312. The sequence in which minerals crystallize from a cooling basaltic magma.
  313. An aquifer completely filled with pressurized water and separated from the land surface by a relatively impermeable confining bed, such as shale.
  314. Boundary separating two plates moving away from each other.
  315. An igneous body that crystallized deep underground.
  316. A giant mountain range that lies under the ocean and extends around the world.
  317. Terrane that did not form at its present site on a continent.
  318. The water that lies beneath the ground surface, filling the cracks, crevices, and pore space of rocks.
  319. Mass wasting in which motion is taking place throughout the moving mass (flow). The common varieties are earthflow, mudflow, and debris avalanche.
  320. A volcano constructed of loose rock fragments ejected from a central vent.
  321. Boundary surface between two different rock types or ages of rocks.
  322. Paper record of earth vibration.
  323. The vast amount of time that preceded the Paleozoic Era.
  324. Sediment composed of particles with a diameter between 1/16 mm and 2 mm.
  325. Rock that forms from crystals precipitating during evaporation of water.
  326. Any of the large crystals in porphyritic igneous rock.
  327. Great fan-shaped deposit of sediment on the deep-sea floor at the base of many submarine canyons.
  328. An area of volcanic eruptions and high heat flow above a rising mantle plume.
  329. Color of a pulverized substance; a useful property for mineral identification.
  330. A sharp peak formed where cirques cut back into a mountain on several sides.
  331. Smallest possible particle of an element that retains the properties of that element.
  332. A rock containing organic matter that is converted to petroleum by burial and other postdepositional changes.
  333. Loose, solid particles that can originate by (1) weathering and erosion of preexisting rocks, (2) chemical precipitation from solution, usually in water, and (3) secretion by organisms.
  334. A basinlike depression over a vent at the summit of a volcanic cone.
  335. Fracture in rock usually filled with late stage magmatic minerals and often containing metal ore. (End Chapter 7)
  336. Principle that states that an original sedimentary layer extends laterally until it tapers or thins at its edges.
  337. An area underlain by one or more oil pools.
  338. The earliest Eon of Earth's history.
  339. A reef attached directly to shore. (See barrier reef.)
  340. A flowing mixture of debris and water, usually moving down a channel.
  341. An epoch of the Quaternary Period characterized by several glacial ages.
  342. Portion of a fold shared by an anticline and a syncline.
  343. At times in the past, colder climates prevailed during which significantly more of the land surface of Earth was glaciated than at present.
  344. Silica-deficient igneous rock with a relatively high content of magnesium, iron, and calcium.
  345. A theoretical concept relating tectonism, erosion, and various rock-forming processes to the common rock types.
  346. Major line of weakness in Earth's crust that crosses the mid-oceanic ridge at approximately right angles.
  347. A resistant ridge of calcium carbonate formed on the sea floor by corals and coralline algae.
  348. Major belt around the edge of the Pacific Ocean on which most composite volcanoes are located and where many earthquakes occur.
  349. A large, rounded landform developed in a massive rock, such as granite, by the process of exfoliation.
  350. Protons and neutrons form the nucleus of an atom. Although the nucleus occupies an extremely tiny fraction of the volume of the entire atom, practically all the mass of the atom is concentrated in the nucleus.
  351. Traces of plants or animals preserved in rock.
  352. Open fissure in a glacier.
  353. A measure of the energy released during an earthquake.
  354. The decomposition of rock resulting from exposure to water and atmospheric gases.
  355. In geology, correlation usually means determining time equivalency of rock units. Rock units may be correlated within a region, a continent, and even between continents.
  356. The capacity of a rock to transmit a fluid such as water or petroleum.
  357. Luster that gives a substance the appearance of being made of something other than metal (e.g., glassy).
  358. A strike-slip fault in which the block seen across the fault appears displaced to the left.
  359. A loss in overall volume and pore space of a rock as the particles are packed closer together by the weight of overlying material.
  360. A fold in which the layered rock usually dips toward an axis.
  361. Boundary surface between two different rock types or ages of rocks.
  362. A bar of marine sediment connecting a former island or stack to the mainland.
  363. An ice-transported boulder that does not derive from bedrock near its present site.
  364. A tabular intrusive structure concordant with the country rock.
  365. A resource that forms at extremely slow rates compared to its rate of consumption.
  366. A drainage pattern consisting of parallel main streams with short tributaries meeting them at right angles. (End Chapter 10)
  367. A plane containing all of the hinge lines of a fold.
  368. A structure in which beds dip away from a central point.
  369. A glacier with a negative budget, which causes the glacier to grow smaller as its edges melt back.
  370. A hard, compact, fine-grained sedimentary rock formed almost entirely of silica.
  371. Gradual loss of heat (per unit of surface area) from Earth's interior out into space.
  372. The bending of seismic waves as they pass from one material to another.
  373. Determining the age of a rock or mineral through its radioactive elements and decay products (previously and somewhat inaccurately called radiometric or radioactive dating).
  374. Breaking waves.
  375. The area in which S waves from the earthquake are absent.
  376. A lake occupying a depression caused by glacial erosion of bedrock.
  377. An earthquake magnitude calculated from the strength of the rock, surface area of the fault rupture, and the amount of rock displacement along the fault.
  378. A ridge of till piled up along the front edge of a glacier.
  379. A theoretical downward limit for stream erosion of Earth's surface.
  380. A line of batholiths or volcanoes. Generally the line, as seen from above, is curved.
  381. Mineral group in which all members are double chain silicates. (Begin Chapter 2)
  382. A glacier confined to a valley. The ice flows from a higher to a lower elevation.
  383. A depression caused by the melting of a stagnant block of ice that was surrounded by sediment.
  384. Iron/magnesium-bearing mineral, such as augite, hornblende, olivine, or biotite.
  385. Rock with a chemical content between felsic and mafic compositions.
  386. A tentative and testable theory. Usually written as an if/then statement.
  387. The location in which deposition occurs, usually marked by characteristic physical, chemical, or biological conditions.
  388. A structure in which the beds dip toward a central point.
  389. A layer of weathered, unconsolidated material on top of bedrock; often also defined as containing organic matter and being capable of supporting plant growth.
  390. A valley-deepening process caused by erosion of a stream bed.
  391. The speed at which water in a stream travels.
  392. The upper surface of the zone of saturation.
  393. Crude oil and natural gas. (Some geologists use petroleum as a synonym for oil.)
  394. A material that forms as the organic matter of buried wood is either filled in or replaced by inorganic silica carried in by ground water.
  395. The overlying surface of an inclined fault plane.
  396. The era that followed the Paleozoic Era and preceded the Cenozoic Era.
  397. A fold overturned to such an extent that the limbs are essentially horizontal.
  398. A new, shorter channel across the narrow neck of a meander.
  399. The rigid outer shell of Earth, 70 to 125 or more kilometers thick.
  400. A stress due to a force pushing together on a body. (Begin Chapter 7)
  401. A fold in which the limbs are parallel to one another.
  402. A single, negative electric charge that contributes virtually no mass to an atom.
  403. The balance or equilibrium between adjacent blocks of crust resting on a plastic mantle.
  404. The vertical distance between points on Earth's surface.
  405. Crystal structure in which all four oxygen ions of a silica tetrahedron are shared by adjacent ions.
  406. The relative ease or difficulty with which a smooth surface of a mineral can be scratched; commonly measured by Mohs' scale.
  407. Mineral with the formula SiO2.
  408. Land-derived sediment that has found its way to the sea floor.
  409. A coastal inlet that is a glacially carved valley, the base of which is submerged.
  410. Change in direction of waves due to slowing as they enter shallow water. (End Chapter 14)
  411. A partially filled aquifer exposed to the land surface and marked by a rising and falling water table.
  412. A relatively steep slope extending from a depth of 100 to 200 meters at the edge of the continental shelf down to oceanic depths.
  413. Cone-shaped mass of dripstone formed on cave floors, generally directly below a stalactite.
  414. A compressional wave (seismic wave) in which rock vibrates parallel to the direction of wave propagation.
  415. Each era of the standard geologic time scale is subdivided into periods (e.g., the Cretaceous Period).
  416. A meander that retains its sinuous curves as it cuts vertically downward below the level at which it originally formed.
  417. Major subdivision of the standard geologic time scale (e.g., Mesozoic Era).
  418. A very rapidly moving, turbulent mass of broken-up bedrock.
  419. Eon of geologic time. Includes all time following the Precambrian.
  420. A coarse-grained sedimentary rock (grains coarser than 2 mm) formed by the cementation of angular rubble.
  421. Slow-to-rapid mass wasting in which debris moves downslope as a very viscous fluid.
  422. Triangular facet where the lower end of a ridge has been eroded by glacial ice.
  423. A body of till either being carried on a glacier or left behind after a glacier has receded.
  424. Stage in the evolution of major mountain belts characterized by the accumulation of great thicknesses (several kilometers) of sedimentary or volcanic rocks.
  425. A broad, flat-topped hill bounded by cliffs and capped with a resistant rock layer.
  426. Stress due to forces that tend to cause movement or strain parallel to the direction of the forces.
  427. Being able to physically follow a rock unit between two places.
  428. Cracks that develop parallel to the outer surface of a large mass of expanding rock, as pressure is released during unloading.
  429. The central zone of Earth.
  430. The point within Earth from which seismic waves originate in an earthquake.
  431. A subatomic particle that contributes mass and a single positive electrical charge to an atom.
  432. Bonding due to the sharing of electrons by adjacent atoms.
  433. The steep, downwind slope of a dune; formed from loose, cascading sand that generally keeps the slope at the angle of repose (about 34°).
  434. A small discordant pluton with an outcropping area of less than 100 square kilometers.
  435. The ability of a rock to break along closely spaced parallel planes.
  436. Depression eroded into the hard rock of a stream bed by the abrasive action of the stream's sediment load.
  437. Rock in which most of the grains are larger than 1 millimeter (igneous) or 2 millimeters (sedimentary).
  438. Rock deposited by precipitation of ions from solution in hot water.
  439. A complex of old Precambrian metamorphic and plutonic rocks exposed over a large area.
  440. Ridge of sand paralleling the shoreline and extending above sea level.
  441. A type of hot spring that periodically erupts hot water and steam.
  442. A fine-grained sedimentary rock (grains finer than 1/16 mm in diameter) formed by the cementation of silt and clay (mud). Shale has thin layers (laminations) and an ability to split (fissility) into small chips.
  443. Rock formed from large pieces of volcanic rock (cinders, blocks, bombs).
  444. An electrically charged atom or group of atoms.
  445. A gaseous mixture of naturally occurring hydrocarbons.
  446. Flood of very high discharge and short duration; sudden and local in extent.
  447. A ferromagnesian mineral with the formula (Fe, Mg)2SiO4.
  448. The way a substance breaks where not controlled by cleavage.
  449. A narrow, deep trough parallel to the edge of a continent or an island arc.
  450. A ridge of sediment, usually sand or gravel, that has been deposited in the middle or along the banks of a stream by a decrease in stream velocity.
  451. An unconformity in which an erosion surface on plutonic or metamorphic rock has been covered by younger sedimentary or volcanic rock.
  452. The process whereby the minerals that crystallize at a high temperature in a cooling magma move downward in the magma chamber because they are denser than the magma.
  453. The gradual straightening of an irregular shoreline by wave erosion of headlands and wave deposition in bays.
  454. A drainage pattern in which streams diverge outward like spokes of a wheel.
  455. An episode of intense deformation of the rocks in a region, generally accompanied by metamorphism and plutonic activity.
  456. Sediment made up of fine-grained clay and the skeletons of microscopic organisms that settle slowly down through the ocean water.
  457. Coarse-grained igneous rock of intermediate composition. Up to half of the rock is plagioclase feldspar and the rest is ferromagnesian minerals.
  458. A single bed with coarse grains at the bottom of the bed and progressively finer grains toward the top of the bed.
  459. Naturally formed, consolidated material composed of grains of one or more minerals. (There are a few exceptions to this definition.
  460. A shallow temporary lake (following a rainstorm) on a flat valley floor in a dry region.
  461. A fault in which the hanging-wall block moved down relative to the footwall block.
  462. Large, symmetrical ridge of sand parallel to the wind direction.
  463. Very flat sediment-covered region of the deep-sea floor, usually at the base of the continental rise.
  464. A group of closely spaced mountains or parallel ridges.
  465. The total number of protons in an atom.
  466. A means of gaining knowledge through objective procedures.
  467. A rock in which most of the mineral grains are less than one millimeter across.
  468. Magma on Earth's surface.
  469. Steplike landform found above a stream and its flood plain.
  470. A reef separated from the shoreline by the deeper water of a lagoon.
  471. A circular reef surrounding a deeper lagoon.
  472. A pronounced sinuous curve along a stream's course.
  473. A region in which the geology is markedly different from that in adjoining regions.
  474. A coarse-grained sedimentary rock (grains coarser than 2 mm) formed by the cementation of rounded gravel.
  475. Huge ocean wave produced by displacement of the sea floor; also called seismic sea wave.
  476. Movement by rolling, sliding, or dragging of sediment fragments along a stream bottom.
  477. The section of the beach exposed to wave action.
  478. Original rock before being metamorphosed.
  479. A strike-slip fault in which the block seen across the fault appears displaced to the right.
  480. The lower edge of a glacier.
  481. A river let down onto a buried geologic structure by erosion of overlying layers.
  482. A crescent-shaped dune with the horns of the crescent pointing downwind.
  483. A type of iron oxide that has a brick-red color when powdered; Fe2O3.
  484. A sedimentary rock composed of fragments of preexisting rock.
  485. A fossil from a very short-lived species known to have existed during a specific period of geologic time.
  486. Bodies of rock (e.g., rock salt) or magma that ascend within Earth's interior because they are less dense than the surrounding rock.
  487. An arrangement of rock fragments bound into a rigid network by cement.
  488. An igneous rock in which large crystals are enclosed in a matrix (or ground mass) of much finer-grained minerals or obsidian.
  489. A subsurface zone in which rock openings are generally unsaturated and filled partly with air and partly with water; above the saturated zone.
  490. A type of iron oxide that is yellowish-brown when powdered; Fe2O3•nH2O.
  491. The settling or coming to rest of transported material.
  492. Scale expressing intensities of earthquakes (judged on amount of damage done) in Roman numerals ranging from I to XII.
  493. A fracture in bedrock along which movement has taken place.
  494. Each period of the standard geologic time scale is divided into epochs (e.g., Pleistocene Epoch of the Quaternary Period).
  495. A long chain (thousands of kilometers) of mountain ranges.
  496. Broad, flat-topped area elevated above the surrounding land and bounded, at least in part, by cliffs.
  497. Dark-colored soil layer that is rich in organic material and forms just below surface vegetation.
  498. Outporuing of lava extruded to Earth's surface.
  499. Very slow, continuous downslope movement of soil or debris. (Begin Chapter 9)
  500. A theory that Earth's surface is divided into a few large, thick plates that are slowly moving and changing in size. Intense geologic activity occurs at the plate boundaries.
  501. A nearly flat surface separating two beds of sedimentary rock.
  502. Underground accumulation of oil.
  503. A subsurface zone in which all rock openings are filled with water.
  504. A fold in which both limbs dip in the same direction.
  505. Greater than average strength of the earth's magnetic field.
  506. A principle or law stating that fossil species succeed one another in a definite and recognizable order; in general, fossils in progressively older rock show increasingly greater differences from species living at present.
  507. A rock in which most of the mineral grains are less than one millimeter across (igneous) or less than 1/16 mm (sedimentary).
  508. Weight per given volume of a substance.
  509. Upper part of a glacier in which there is no plastic flow.
  510. The lowering of the water table near a pumped well.
  511. The era that followed the Precambrian and began with the appearance of complex life, as indicated by fossils.
  512. The movement of eroded particles by agents such as rivers, waves, glaciers, or wind.
  513. Rounded by weathering from an initial blocky shape.
  514. On minerals, extremely straight, parallel lines. (End Chapter 2)
  515. See tsunami.
  516. Volcanic glass.
  517. Conical mountain rising 1,000 meters or more above the sea floor.
  518. An explanation for observed phenomena that has a high possibility of being true.
  519. The compass direction in which the angle of dip is measured.
  520. Elongate region in which subduction takes place.
  521. Various different species of fossils in a rock.
  522. A stress due to a force pushing together on a body.
  523. The temperature below which a material becomes magnetized.
  524. A seismic wave propagated by a shearing motion, which causes rock to vibrate perpendicular to the direction of wave propagation.
  525. Any igneous rock that forms at Earth's surface, whether it solidifies directly from a lava flow or is pyroclastic.
  526. A long, sinuous ridge of sediment deposited by glacial meltwater.
  527. Highly leached soil that forms in regions of tropical climate with high temperatures and very abundant rainfall.
  528. A boundary between two plates that are moving toward each other.
  529. A fold in which the hinge line (or axis) is not horizontal.
  530. A soil layer composed of incompletely weathered parent material.
  531. An arrangement of layers or beds of rock. (Begin Chapter 6)
  532. A tabular intrusive structure concordant with the country rock. (End Chapter 6)
  533. A very flat surface underlain by hard, mud-cracked clay.
  534. Large angular pyroclast.
  535. A depression on the land surface caused by wind erosion.
  536. Pressure applied equally on all surfaces of a body; also called geostatic or lithostatic pressure.
  537. Block of glacier-derived ice floating in water.
  538. A worldwide relative scale of geologic time divisions.
  539. Small shifting river channel that carries water away from the main river channel and distributes it over a delta's surface.
  540. The oldest eon of Earth's history.
  541. A sedimentary rock composed mostly of the mineral dolomite.
  542. Rounded particles coarser than 2 mm in diameter.
  543. Sediment composed of particles with diameter less than 1/256 mm.
  544. A range created by uplift along normal or vertical faults.
  545. A low ridgelike pile of till along the side of a glacier.
  546. A plot of seismic-wave arrival times against distance.
  547. Fine-grained material found in the pore space between larger sediment grains.
  548. When pressures on a body are not of equal strength in all directions.
  549. Line dividing one drainage basin from another.
  550. The outer layer of rock, forming a thin skin over Earth's surface.
  551. A portion of a major mountain belt characterized by large thrust faults, stacked one upon another. Layered rock between the faults was folded when faulting was taking place.
  552. The sequence in which events took place (not measured in time units).
  553. Material deposited by debris-laden meltwater from a glacier.
  554. A boundary between two plates that are moving toward each other.
  555. A smaller valley that terminates abruptly high above a main valley.
  556. A fault in which movement is parallel to the strike of the fault surface.
  557. The vertical distance between the crest (the high point of a wave) and the trough (the low point).
  558. A rock formed or apparently formed from solidification of magma.
  559. The region on Earth's surface, 103° to 142° away from an earthquake epicenter, in which P waves from the earthquake are absent.
  560. Ground that remains permanently frozen for many years.
  561. A surface that represents a break in the geologic record, with the rock unit immediately above it being considerably younger than the rock beneath.
  562. A subatomic particle that contributes mass to an atom and is electrically neutral.
  563. Stream that loses water to the zone of saturation.
  564. The transformation of preexisting rock into texturally or mineralogically distinct new rock as a result of high temperature, high pressure, or both, but without the rock melting in the process.
  565. The situation in mass wasting that occurs when material free-falls or bounces down a cliff.
  566. A hydrous aluminum-silicate that occurs as a platy grain of microscopic size with a sheet silicate structure.
  567. A representation of a portion of Earth in a vertical plane.
  568. An apparent movement of the earth's poles.
  569. A tabular, discordant intrusive structure.
  570. A volcano constructed of alternating layers of pyroclastics and rock solidified from lava flows.
  571. A mineral of commercial value.
  572. Mechanical weathering of rock by freezing water.
  573. Glacier with a positive budget, so that accumulation results in the lower edges being pushed outward and downward.
  574. Parallel alignment of textural and structural features of a rock.
  575. A narrow pinnacle of resistant rock with a flat top and very steep sides.
  576. Crystal development and growth.
  577. Metamorphism coupled with the introduction of ions from an external source.
  578. Any of the small ridges formed on sediment surfaces exposed to moving wind or water. The ridges form perpendicularly to the motion.
  579. Group of most common minerals of Earth's crust. All feldspars contain silicon, aluminum, and oxygen and may contain potassium, calcium, and sodium.
  580. A substance that cannot be broken down to other substances by ordinary chemical methods. Each atom of an element possesses the same number of protons.
  581. The solid material that precipitates in the pore space of sediments, binding the grains together to form solid rock.
  582. A sedimentary rock formed from the consolidation of plant material. It is rich in carbon, usually black, and burns readily.
  583. The underlying surface of an inclined fault plane.
  584. A fault in which the hanging-wall block moved up relative to the footwall block.
  585. Rock composed entirely or almost entirely of ferromagnesian minerals.
  586. A lake formed during an earlier time of abundant rainfall.
  587. Less than normal gravitational attraction.
  588. A rock composed of material precipitated directly from solution.
  589. A broad strip of land built up by sedimentation on either side of a stream channel.
  590. A type of surface seismic wave that causes the ground to move side to side in a horizontal plane perpendicular to the direction the wave is traveling.
  591. The rise of Earth's crust after the removal of glacial ice.
  592. Atoms (of the same element) that have different numbers of neutrons but the same number of protons.
  593. Iciclelike pendant of dripstone formed on cave ceilings.
  594. Metamorphism under conditions in which high temperature is the dominant factor.
  595. A body of saturated rock or sediment through which water can move readily. (Begin Chapter 11)
  596. Turbulent mixture of pyroclastics and gases flowing down the flank of a volcano.
  597. A feldspar with the formula KAlSi3O8.
  598. A hole, generally cylindrical and usually walled or lined with pipe, that is dug or drilled into the ground to penetrate an aquifer below the zone of saturation. (End Chapter 11)
  599. A felsic, coarse-grained, intrusive igneous rock containing quartz and composed mostly of potassium- and sodium-rich feldspars.
  600. Region of magnetic force that surrounds Earth.
  601. Hard, rounded mass that develops when a considerable amount of cementing material precipitates locally in a rock, often around an organic nucleus.
  602. Movement of sediment parallel to shore when waves strike a shoreline at an angle.
  603. Downhill slope of a stream's bed or the water surface, if the stream is very large.
  604. A stream that exhibits a delicate balance between its transporting capacity and the sediment load available to it.
  605. Shale with a high content of organic matter from which oil may be extracted by distillation.
  606. A line along which the temperature of rock (or other material) is the same.