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2011-04-27 22:40:11

Geology terms from the book
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  1. _________ explores the many and varied interactions between humans and that geologic environment.
    environmental geology 3
  2. The eventual result wass an earth differentiated into several major compositional zones: the central _____; the surrounding _______; and a thin ______ at the surface.
    core, mantle, crust 7
  3. The ________ is a means of discovering basic scientific principles.
    scientific method 10
  4. One or more ________ are formulated to explain the observations or data.
    hypotheses 10
  5. A hypothesis that is repeatedly supported by new experiments advances in time to the status of a _____, a generally accepted explanation for a set of data or observations.
    theory 10
  6. Even when the population growth rate is constant, the number of individuals added per unit of time increases over time called _________.
    exponential growth 15
  7. Another way to look at the rapidity of world population growth is to consider the expected ________, the length of time required for a population to double in size.
    doubling time 15
  8. Some scholars believe that we are already on the verge of exceeding the earth's ________, its ability to sustain its population at a basic, healthy, moderately comfortable standard of living.
    carrying capacity 17
  9. An ______ is the smallest particle into which an element can be divided while still retaining the chemical characteristics of that element.
    atom 24
  10. The ________, at the center of the atom, contains one or more particles with a positive electrical charge (______) and usually some particles of similar mass that have no charge (_______).
    nucleus, protons, neutrons 24
  11. Circling the nucleus are the negatively charged _________.
    electrons 24
  12. The sum of the number of protons and the number of neutrons in a nucleus is the atom's ________.
    atomic mass number 24
  13. Atoms of a given element with different atomic mass numbers- in other words, atoms with the same number of protons but different number of neutrons- are distinct ________ of that element.
    isotopes 24
  14. Most atoms, however, can gain or lose some electrons. When this happens, the atom has a positive or negative charge and is called an _______.
    ion 24
  15. Positively and negatively charged ions are called, respectively, ______ and ______
    cations and anions 24
  16. Some idea of the probable chemical behavior of elements can be gained from a knowledge of the __________.
    periodic table 25
  17. A ________ is a chemical combination of 2 or more chemical elements, bonded together in particular proportions, that has a distinct set of physical properties (often very different from those of any of the individual elements in it).
    compound 25
  18. In __________, the bond is based on the electrical attraction between oppositely charged ions.
    ionic bonding 26
  19. Bonds between atoms may also form if the atoms share electrons called ________.
    covalent bonding 26
  20. A _________ is a naturally occurring, inorganic, solid element or compound with a definite chemical composition and a regualar internal crystal structure.
    mineral 26
  21. __________ materials are solids in which the atoms or ions are arranged in regular, repeating patterns.
    crystalline 26
  22. Not only is the external form of crystals related to their internal structure; so is _______, a distinctive way some minerals break up when struck.
    cleavage 29
  23. It comes as no surprise, therefore, that by far the largest compositional group of minerals is the _______ group, all of which are compounds containing silicon and oxygen, and most of which contain other elements as well.
    silicate 30
  24. _________ is the general term used to describe those silicates- usually dark- colored (black, brown or green)- that contain iron and/or magnesium, with or without additional elements.
    ferromagnesian 31
  25. The __________ all contain carbon and oxygen combined in the proportions of one atom of carbon to 3 atoms of oxygen (written CO3).
    carbonates 31
  26. The _______ all contain sulfur and oxygen in the ration of 1:4 (SO4).
    sulfates 31
  27. When sulfur is present without oxygen, the resultant minerals are called ________.
    sulfides 32
  28. Minerals containing just one or more metals combined with oxygen, lacking the other elements necessary to classify them as silicates, sulfates, carbonates, and so forth, are the _________.
    oxides 33
  29. __________ are minerals that consist of a single chemical element, and the minerals' names are usually the same as the corresponding elements.
    native elements 33
  30. The essence of the concept of the ________, explored more fully at the end of this chapter, is that rocks, far from being the permanent objects we may imagine them to be, are continually being changed by geological processes.
    rock cycle 34
  31. ________ is the name given to naturally occurring hot, molten rock material.
    magma 34
  32. An _______ rock is a rock formed by the solidification and crystallization of a cooling magma.
    igneous 34
  33. Under these conditions, the crystals have ample time to form and to grow very large and the rock eventually formed has mineral grains large enough to be seen individually with the naked eye. Arock formed in this way is a ________ igneous rock.
    plutonic 35
  34. A magma that flows out on the earth's surface while still wholly or partly molten is called _______.
  35. Lave is a common product of volcanic eruptions, and the term _______ is given to an igneous rock formed at or close to the earth's surface.
    volcanic 35
  36. In extreme cases, where cooling occurs very fast, even tiny crystals may not form before the magma solidifies, and its atoms are frozen in a disordered state. The resulting clear, noncrystalline solid is a natural ________, obsidian.
    glass 36
  37. At the lower end of the spectrum of rock-formation temperatures are the ___________ rocks.
    sedimentary 37
  38. _________ are loose, unconsolidated accumulations of mineral or rock particles that have been transported by wind, water, or ice, or shifted under the influence of gravity, and redeposited.
    sediments 37
  39. The set of processes by which sediments are transformed into rock is collectively described as _________.
    lithification 37
  40. ___________ are formed from the products of the mechanical breakup of other rocks.
    Clastic sedimentary rocks 37
  41. __________ form not from mechanical breakup and transport of fragments, but from crystals formed by precipitation or growth from solution.
    chemical sedimentary rocks 37
  42. A sequence of sedimentary rocks may include layers of _________, carbon-rich remains of living organisms; coal is an important example, derived from the remains of land plants that flourished and died in swamps.
    organic sediments 37
  43. A __________ rock is on that has formed from another, preexisting rock that was subjected to heat and/or pressure.
    metamorphic 39
  44. When hot magma formed at depth rises to shallower levels in the crust, it heats the adjacent, cooler rocks, and they may be metamorphosed; this is __________.
    contact metamorphism 39
  45. Metamorphism can also result from the stresses and heating to which rocks are subject during mountain building or plate-tectonic movement. Such metamorphism on a large scale, not localized around a magma body, is ___________.
    regional metamorphism 39
  46. In a rock subjected to directed stress, minerals that form elongated or platy crystals may line up parallel to each other. The resultant texture is described as _________.
    foliation 39
  47. He proposed that all the continental landmasses had once formed a single supercontinent, Pangea, which had them split apart, the modern continents moving to their present positions via a process called __________.
    continental drift 46
  48. __________ is the study of large scale movement and deformation of the earth's layers.
    tectonics 46
  49. __________ relates such deformation to the existence and movement of rigid "plates"over a weaker, more plastic layer in the earth's upper mantle.
    plate tectonics 47
  50. An object is under ________ when force is being applied to it.
    stress 46
  51. The stress may be __________, tending to squeeze or compress the object, or it may be ________, tending to pull the object apart.
    compressive, tensile 46
  52. A ___________is one that tends to cause different parts of the object to move in different directions across a plane or to slide past one another, as when a deck of cards is spread out on a tabletop by a sideways sweep of the hand.
    shearing stress 46
  53. _________ deformation resulting from stress. It may be temporary or permanent, depending on the amount and type of stress and on the physical properties of the material.
    strain 46
  54. If __________ occurs, the amount of deformation is porportional to the stress applied, and the material returns to its original size and shape when the stress is removed.
    elastic deformation 46
  55. Once the _________ of a material is reached, the material may go through a phase of _________ with increased stress. During this stage, relatively small added stresses yield large corresponding strains, and the changes are permanent: the material does not return to its original shape after removal of stress.
    elastic limit, plastic deformation 46
  56. If stress is increased sufficiently, most solids eventually break, or ________.
    rupture 47
  57. In _______ materials, rupture may occur before there is any plastic deformation.
    brittle 47
  58. Together they make up the outer solid layer of the earth called the _________.
    lithosphere 48
  59. The layer below the lithosphere is the _________.
    asthenosphere 48
  60. Each magnetic mineral has a __________, the temperature below which it remains magnetic, but above which it loses its magnetic properties.
    curie temperature 50
  61. This is the basis for the study of __________, "fossil magnetism" in rocks.
    paleomagnetism 51
  62. Thus was born the concept of _________, the moving apart of lithospheric plates at the ocean ridges.
    seafloor spreading 52
  63. The resulting curve, showing the apparent movement of the magnetic pole relative to the continent as a function of time, is called the ________ for that continent.
    polar wander curve 52
  64. At a _________, lithospheric plates move apart.
    divergent plate boundary 55
  65. This type of plate boundary, where one plate is carried down below (subducted beneath) another, is called a _________.
    subduction zone 56
  66. At a _________, as the name indicates, plates are moving toward each other.
    convergent plate boundary 56
  67. The offset is a special kind of fault, or break in the lithosphere, known as a ________.
    transform fault 59
  68. Another way to monitor rates and directions of plate movement is by using mantle _______. These are isolated aeas of volcanic activity usually not associated with plate boundaries.
    hot spots 60
  69. For many years, the most widely accepted explanation was that the plates were moved by large _________ slowly churning in the plastic asthenosphere.
    convection cells 61
  70. They occur along _______, planar breaks in rock along which there is displacement of one side relative to the other.
    faults 67
  71. When movement along faults occurs, gradually and relatively smoothly, it is called ______.
    creep 67
  72. When the stress at last exceeds the rupture strength of the rock (or the friction along a preexisting fault), a sudden movement occurs to release the stress. This is an ________, or seismic slip.
    earthquake 68
  73. With the sudden displacement and associated stress release, the rocks snap back elastically to their previous dimensions; this behavior is called _________.
    elastic rebound 68
  74. The point on the earth's surface direct;y above the focus is called the ________.
    epicenter 69
  75. A _________, them is one along which the displacement is parallel to the strike (horizontal).
    strike-slip fault 69
  76. A _________ is one in which the displacement is vertical, up or down in the direction of dip.
    dip-slip fault
  77. Convergent plate boundaries are often characterized by ________, which are just reverse faults with relatively shallowly dipping fault planes.
    thrust faults 69
  78. When an earthquake occurs, it releases the stored-up energy in ________ that travel away from the focus.
    seismic waves 70
  79. ________( P waves and S waves) travel through the interior of the earth.
    Body waves 70
  80. ________ are compressional waves. As they travel through matter, the matter is alternately compressed and expanded.
    P waves 70
  81. ________ are shear waves, involving a side-to-side motion of molecules. Shear-type waves can also be demonstrated with a Slinky by streatching the coil out along the ground as before, but this time twitching one end of the coil sideways (perpendicular to its length).
    S waves 70
  82. Seismic ________ are somewhat similar to surface waves on water. That is, they cause rocks and soil to be displaced in such a way that the ground surface ripples or undulates.
    surface waves
  83. Both types of body waves cause ground motions that are detectable using a _________.
    seismograph 71
  84. The amount of ground motion is related to the _________ of the earthquake.
    magnitude 72
  85. An alternative way of describing the size of an earthquake is by the earthquake's __________.
    intensity 73
  86. For example, severe earthquakes are generally followed by many _________, earthquakes that are weaker than the principal tremor.
    aftershocks 77
  87. The problem is __________. When wet soil is shaken by an earthquake, the soil particles may be jarred apart, allowing water to seep in between them, greatly reducing the friction between soil particles that gives the soil strength, and causing the ground to become somewhat like quick sand.
    liquefaction 79
  88. Coastal areas, especially around the Pacific Ocean basin where so many large earthquakes occur may also be vulnerable to _________. These are seismic sea waves, sometimes improperly called "tidal waves," although they have nothing to do with tides.
    tsunamis 80
  89. Such quiescent, or dormant, sections of otherwise- active fault zones are called _________.
    seismic gaps 84
  90. In its early stages, earthquakes prediction was based particularly on the study of earthquake ___________, things that happen or rock properties that change prior to an earthquake.
    precursor phenomena 84
  91. This accounts for the _______ (mafic volcanic rock) that forms new sea floor at spreading ridges.
    basalt 95
  92. At a continental rift zone, the asthenosphere-derived melt is also mafic, but the rising hot basaltic magma may warm the more granite continental crust enough to produce some silica-rich melt also- making ________, the volcanic equivalent of granite- or the basaltic magma may incorporate some crustal material to make _______, intermediate in composition between the mafic basalt and felsic rhyolite.
    rhyolite, andesite 95
  93. The outpouring of magma at spreading ridges is an example of ________, the eruption of magma out of a crack in the lithosphere, rather than from a single pipe or vent.
    fissure eruption 96
  94. This low, shieldlike shape has led to the term _________ for such a structure.
    shield volcano 97
  95. The bits of violently erupted volcanic material are described collectively as _______.
  96. The cinders may pile up into a very symmetric cone-shaped heap known as a ________.
    cinder cone 98
  97. Many volcanoes erupt somewhat different materials at different times. They may emit some pyroclastics, then some lava, then more pyroclastics, and so on. Volcanoes build up in this layer-cake fashion are called_________, or alternately, _________, because they are built up of layers of more than one kind of material.
    stratovolcanoes, composite volcanoes 98
  98. When not erupting explosively, the slow-flowing rhyolitic and andesitic lavas tend to ooze out at the surface like thick toothpaste form a tube, piling up close to the volcanic vent, rather than spreading freely. The resulting structure is a compact and steep-sided _________.
    lava dome 98
  99. Volcanic ash and water can combine to create a fast-moving volcanic mudflow called a ________.
    lahar 103
  100. Another special kind of pyroclastic outburst is a deadly, denser-than-air mixture of hot gases and fine ash that forms a hot ___________, quite different in character from a rain of ash and cinders.
    pyroclastic flow 104
  101. In the case of a volcanic island, large quantities of seawater may seep down into the rock, come close to the hot magma below, turn to steam, and blow up the volcano like an overheated steam boiler. This is called a ___________ or explosion.
    phreatic eruption 110
  102. A volcano is generally considered _______ if it has erupted with recent history.
    active 111
  103. When the volcano has not erupted recently but is fresh-looking and not too eroded or worn down, it is regarded as _______: inactive for the present but with the potential to become active again.
    dormant 111
  104. Historically, a volcano that has no recent eruptive history and appears very much eroded has been considered ________, or very unlikely to erupt again.
    extinct 111
  105. The ____________ has been developed as a way to characterize the relative sizes of explosive eruptions.
    Volcanic Explosiveity Index (VEI) 112
  106. A _______ is an enlarged volcanic crater, which may be formed either by an explosion enlarging an existing crater or by collapse of a volcano after a magma chamber within has emptied.
    caldera 119
  107. The _________ includes all the water at and near the surface of the earth.
    hydrosphere 125
  108. All of the water in the hydrosphere is caught up in the __________.
    hydrologic cycle 125
  109. A ________ is any body of flowing water confined within a channel, regardless of size, although people tend, informally, to use the term river for a relatively large stream.
    stream 125
  110. The region from which a stream draws water is its _________, or watershed.
    drainage basin 125
  111. The size of a stream may be described by its _________, the volume of water flowing past a given (or, more precisely, through a given cross section) in a specified length of time.
    discharge 126
  112. The total quanity of material that a stream transports by all these methods is called, simply, its ________.
    load 126
  113. Stream ________ is a measure of the total load of material a stream can move.
    capacity 12
  114. The steepness of the stream channel is called its _________.
    gradient 127
  115. Near the mouth, the stream is approaching its _______, which is the lowest elevation to which the stream can erode downward.
    base level 127
  116. The __________ of such a stream (a sketch of the stream's elevation from source to mouth) assumes a characteristic concave-upward shape.
    longitudinal profile 128
  117. The relationship between the velocity of water flow and the size of particles moved accounts for one characteristic of stream-deposited sediments: They are commonly _________ by size and density, with materials deposited at a given point tending to be similar in size or weight.
    well sorted 129
  118. If the stream is still carrying a substantial load as it reaches its mouth, and it then flows into still waters, a large, fan-shaped pile of sediment, a ______, may be built up.
    delta 129
  119. A similarly shaped feature, an __________, is formed when a tributary stream flows into a more slowly flowing, large stream, or a stream flows from mountains into a plain.
    alluvial fan 130
  120. Bends, or _________, thus begin to form in the stream.
    meanders 130
  121. It is eroded on the outside and downstream side of the meander, the _________, where the water flows somewhat faster (and the channel, too, tends to be a little deeper there as a result); _________, consisting of sediment deposited on the insides of meanders, build out the banks in those parts of the channel.
    cut bank, point bar 130
  122. If the sediment load is very large in relation to water volume, the ________ may develop a complex pattern of many channels that divide and rejoin, shifting across a broad expanse of sediment.
    braided stream 130
  123. This is the stream's _________, the area into which the stream spills over during floods.
    floodplain 131
  124. The cutoff meaners are called _______.
    oxbows 131
  125. When rainfalls or snow melts, some of the water sinks into the ground (_________).
    infiltration 131
  126. Below ground, _________ moves it through soil and rock.
    percolation 131
  127. In times of higher discharge, the stream may overflow its banks, or _________.
    flood 131
  128. The elevation of the water surface at any point is termed the ________ of the stream.
    stage 133
  129. The stream is said to _______ when the maximum stage is reached.
    crest 133
  130. Floods that affect only small, localized areas (or streams draining small basins) are sometimes called _________.
    upstream floods 133
  131. Floods that affect large stream systems and large drainage basins are called _________.
    downstream floods 133
  132. Fluctuations in stream stage or discharge over time can be plotted on a ________. Hydrographs spanning long periods of time are very useful in constructing a picture of the "normal" behavior of a stream and of that stream's response to flood-causing events.
    hydrograph 133
  133. Long-term records make it possible to construct a curve showing discharge as a function of recurrence interval for a particular stream or section of one called __________.
    flood-frequency curve 135
  134. A flood event can then be described by its __________: how frequently a flood of that severity occurs, on average, for that stream.
    recurrence interval 135
  135. Ifopen land is available, flood hazards along a stream may be greatly reduced by the use of __________. These ponds are large basins that trap some of the surface runoff, keeping it from flowing immediately into the stream.
    retention ponds 141
  136. ___________ is a general term for various modifications of the stream channel itself that are usually intended to increase the velocity of water flow, the volume of the channel, or both.
    Channelization 141
  137. The problem that local modifications may increase flood hazards elsewhere is sometimes also a complication with the building of ________, raised banks along a stream channel.
    levees 142
  138. The western margin of North America is an ________, one at which there is an active plate boundary, with various sections of it involved in subduction or transform faulting.
    active margin 151
  139. The eastern margin of North America is a _________, far removed from the active plate boundary at the Mid-Atlantic Ridge.
    passive margin 151
  140. A ________ is a gently sloping surface washed over by the waves and covered by sediment.
    beach 151
  141. The ________ is that portion regularly washed by the waves as tides rise and fall.
    beach face 151
  142. The most effective erosion of solid rock along the shore is through wave action- either the direct poinding by breakers or the grinding effect of sand, pebbles, and cobbles propelled by waves, which is called _______, or abraison
    milling 151
  143. When waves approach a beach at an angle, as the water washes up onto and down off the beach, there is also net movement of water laterally along the shoreline, creating a _________.
    longshore current 153
  144. The net result is __________, gradual sand movement down the beach in the same general direction as the motion of the longshore current.
    littoral drift 153
  145. This, coupled with strong onshore winds piling water against the land, can result in unusually high water levels during the storm, a storm _______.
    surge 153
  146. A distinctive coastal feature that develops where the land is rising and/or the water level is falling is a set of __________.
    wave-cut platforms 156
  147. A portion of the floodplain may be filled by encroaching seawater, and the fresh water backs up above the new, higher base level, forming a __________.
    drowned valley 157
  148. Jutting points of land, or headlands, are more actively under attack than recessed bays because wave energy is concentrated on these headlands by _________, deflection of the waves around irregularities in the coastline.
    wave refraction 161
  149. __________ are long, low, narrow islands paralleling a coastline somewhat offshore from it.
    barrier islands 163
  150. An _________ is a body of water along a coastline, open to the sea, in which the tide rises and falls and in which fresh and salt water meet and mix to create brackish water.
    estuary 165
  151. It tugs constantly downward on every mass of material everywhere on earth, causing a variety of phenomena collevtively called _________, or _________.
    mass wasting, mass movement 171
  152. _________ is a general term for the results of rapid mass movements.
    landslide 171
  153. The downslope pull tending to cause mass movements, called the _________, is related to the mass of material and the slope angle.
    shearing stress 172
  154. Counteracting the shearing stress is friction, or, in a coherent solid, _________.
    shear strength 172
  155. For dry, unconsolidated material, the ____________ is the maximum slope angle at which the material is stable.
    angle of repose 172
  156. True _________ are most common in northern polar latitudes.
    quick clays 177
  157. The grinding and pulverizing action of massive glaciers can produce a ________ of clay-sized particles, less than .02 millimeter in diameter.
    rock flour 177
  158. So-called _________ are somewhat similar in behavior to quick clays but may be formed from different materials.
    sensitive clays 177
  159. When downslope movement is quite slow, even particle by particle, the motion is described as _______.
    creep 177
  160. A _______ is a free-falling action in which the moving material is not always in contact with the ground below.
    fall 177
  161. Falls are most often _______.
    rockfalls 177
  162. The coarse rubble that accumulates at the foot of a slope prone to rockfalls is _________.
    talus 178
  163. In a ________, a fairly cohesive unit of rock or soil slips downward along a clearly defined surface or plane.
    slide 178
  164. __________ can occur in rock or soil. A rotational movement of the soil mass typically accompanies the downslope movement. A scarp may be formed at the top of the slide.
    slumps 179
  165. In a ________, the material moved is not coherent but moves in a more chaotic, disorganized fashion, with mixing of particles within the flowing mass, as a fluid flows.
    flow 179
  166. A flow involving a wide variety of materials- soil, rocks, trees, and so on- together in a single flow is a __________ , or __________, the latter term more often used for water- saturated debris.
    debris avalanche, debris flow 179
  167. A _________ is a mass of ice that moves over land under its own weight, through the action of gravity.
    glacier 196
  168. Glaciers are divided into 2 types on the basis of size and occurence. The most numerous today are the ________, also know as mountain or valley glaciers.
    alpine glaciers 197
  169. The larger and rarer ___________ are also know as ice caps or ice sheets.
    continental glaciers 197
  170. At some point, the advancing edge of the glacier terminates, either because it flows out over water and breaks up, creating icebergs by a process known as _________, or, more commonly, because it has flowed to a place that is warm enough that ice loss by melting or evaporation is at least as rapid as the rate at which new ice flows in.
    calving 198
  171. The set of processes by which ice is lost from a glacier is collectively called _________.
    abalation 198
  172. The _____________ is the line on the glacial surface where there is no net gain or loss of material.
    equilibrium line 198
  173. On a very small scale, bits of rock that have become frozen into the ice at the base of a glacier act like sandpaper on solid rock below, making fine, parallel scratches, called _______, on the underlying surface.
    striations 200
  174. Erosion by the scraping of ice or included sediment on the surface underneath is ________.
    abrasion 200
  175. Some of the till may be transported and redeposited by the meltwater, whereupon the resultant sediment is called _________.
    outwash 200
  176. Till and outwas together are 2 varieties of glacial ________.
    drift 200
  177. A landform made of till is called a _________.
    moraine 201
  178. Where winds blow consistently form certain directions, exposed boulders may be planed off in the direction(s) from which they have been abraded, becoming ________ ("wind-made" rocks).
    ventifacts 208
  179. _________ is the wholesale removal of loose sediment, usually fine-grained sediment, by the wind.
    deflation 208
  180. Where sediment is transported and deposited by wind, the principal depositional feature is a _______, a low mound or ridge, usually made of sand.
    dune 209
  181. They pile up a bit at the peak, like windswept snow cornices on a mountain, then tumble down the steeper face, or _________, which tends to assume a slope at the angle of repose of sand (or whatever size of particle is involved)
    slip face 209
  182. A deposit of windblown silt is known as ________.
    loess 210
  183. Mamy of the features of wind erosion and deposition are most readily observed in __________.
    deserts 210
  184. Under these conditions, much of the moisture originally in the sir mass is forced out as precipitation, and the air is much drier when it moves farther inland and down out of the mountains. In effect, the mountain cast a ________ on the land beyond.
    rain shadow 213
  185. The term ___________, however, is generally restricted to apply only to the relatively rapid development of deserts caused by the impact of human activities.
    desertification 213
  186. In turn, heat (infrared rays) radiating outward from earth's surface may or may not be trapped by certain atmospheric gases, a phenomenon known as the ____________.
    greenhouse effect 217
  187. The permanently frozen zone is __________.
    permafrost 219
  188. The roles of temperature and salinity are refleted in the name __________ (remember, "halite" is sodium chloride, salt, the most abundant dissolved material in the oceans) given to the largest scale circulation of the oceans.
    thermohaline circulation 221
  189. __________ is the proportion of void space in the material- holes or cracks, unfilled by solid material, within or between individual mineral grains- and is a measure of how much fluid the material can store.
    porosity 240
  190. __________ is a measure of how readily fluids pass through the material.
    permeability 240
  191. Immediately above the impermeable material is a volume of rock or soil that is water-saturated, in which water fills all the accessible pore space, the __________, or ___________.
    saturated zone, phreatic zone 241
  192. ___________ is the water in the saturated zone.
    groundwater 241
  193. Above the saturated zone is rock or soil in which the pore spaces are filled partly with water, partly with air: the ___________, or ___________.
    unsaturated zone, vadose zone 241
  194. The water in unsaturated soil is _________, and is often an important factor in agricultural productivity.
    soil moisture 241
  195. The _________ is the top surface of the saturated zone, where the saturated zone is not confined by overlying impermeable rocks.
    water table 241
  196. The processes of infiltration and migration or percolation by which ground water is replaced are collectively called _________.
    recharge 241
  197. Groundwater ________ occurs where ground water flows into stream, escapes at the surface in a spring, or otherwise exits the aquifer.
    discharge 241
  198. A rock that holds enough water and transmits it rapidly enough to be useful as a source of water is an _________.
    aquifer 242
  199. An __________ is a rock that may store a considerable quanity of water, but in which water flow is slowed, or retarded; that is , its permeability is low, regardless of its porosity.
    aquitard 242
  200. When the aquifer is directly overlain only by permeable rocks and soil, it is described as an ___________.
    unconfined aquifer 242
  201. A __________ is bounded above and below by low-permeability rocks (aquitards).
    confined aquifer
  202. If a well is drilled into a confined aquifer, the water can rise above its level in the aqufer because of the extra hydrostatic (fluid) pressure. This is called an _________.
    artesian system 243
  203. In such a system, rather than describing the height of the water table, geologists refer to the height of the __________, which represents the height to which the water's pressure would raise the water if the water were unconfined.
    potentiometric surface 243
  204. How readily ground water can move through rocks and soil is governed by permeability, but where and how rapidly it actually does flow is also influenced by differences in _________( potential energy) from place to place.
    hydraulic head 243
  205. The height of the water table (in an unconfined aquifer) or of the potentiometric surface (confined aquifer) reflects the hydraulic head at each point in the aquifer. All else being equal, the greater the difference in hydraulic head between 2 points, the faster ground water will flow betweem them. This is a key result of _________.
    Darcy's Law 243
  206. In an unconfined aquifer, the result is a circular lowering of the water table immediately around the well, which is called a _________.
    cone of depression 244
  207. A further problem arising from groundwater use in coastal regions, aside from the possibility of surface subsidence, is __________.
    saltwater intrusion 247
  208. Dissolution of these rocks by subsurface water, and occasional collapse or subsidence of the ground surface into the resultant cavities, creates a distinctive terrain known as _________.
    karst 248
  209. There may be no obvious evidence at the surface of what is taking place until the ground collapses abruptly into the void, producing a __________.
    sinkhole 251
  210. ___________ simply contains substantial amounts of dissolved calcium and magnesium.
    hard water 253
  211. __________ is defined in different ways for different purposes. Engineering geologists define it very broadly to include all unconsolidated material overlying bedrock.
    soil 270
  212. _________ also called physical weathering, is the physical breakup of rocks without changes in the rocks' composition.
    mechanical weathering 270
  213. ___________ involves the breakdown of minerals by chemical reaction with water, with other chemicals disolved in water, or with gases in the air.
    chemical weathering 270
  214. At the very top is the _______, consisting wholly of organic matter, whether living or decomposed- growing plants, decaying leaves, and so on.
    O horizon 273
  215. Below that is the ________. It consists of the most intensicely weathered rock material, being the zone most exposed to surface processes, mixed with organic debris from above.
    A horizon 273
  216. Unless the local water table is exceptionally high, precipitation infiltrates down through the A horizon and below. In so doing, the water may dissolve soluble minerals and carry them away with it. This process is known as _________, and it may be especially intense just below the A horizon, as acids produced by the decay of organic matter seep downward with percolating water.
    leaching 273
  217. The _____, below the A horizon, is therefore also known as the zone of leaching. Fine grained minerals, such as clays, may also be washed downward through this zone.
    E horizon 273
  218. Many of the minerals leached or extracted from the E horizon accumulate in the layer below, the _________, also known as the ___________.
    B horizon, zone of accumulation 274
  219. Below the B horizon is a zone consisting principally of very coarsely broken-up bedrock and little else. This is the __________, which does not resemble out usual idea of soil at all.
    C horizon 274
  220. The ________ soils were seen as characteristic of more humid regions where the climate is wetter, there is naturally more extensive leaching of the soil, and what remains is enriched in the less-soluble oxides and hydroxides of aluminum and iron, with clays accumulated in the B horizon.
    pedalfer 275
  221. From this observation came the term _________ for the soil of a dry climate. The presence of calcium carbonate makes it more alkaline.
    pedocal 275
  222. A ________ may be regarded as an extreme kind of pedalfer. They develop in tropical climates with high temperatures and heavy rainfall, so they are severely leached.
    laterite 277
  223. A given ore deposit may be described in terms of the enrichment or ______________ of a metal of interest.
    concentration factor 292
  224. ___________ is the term given to unusually coarse-grained igneous intrusions.
    pegmatite 292
  225. An _________ is a rock in which a valuable or useful metal occurs at a concentration sufficiently high, relative to average rocks, to make it economically worth mining.
    ore 292
  226. They are mined primarily from igneous rocks called _________, which occur as pipe-like intrusive bodies that must have originated in the mantle.
    kimberlites 294
  227. In time, the fluids cool and deposit their dissolved minerals, creating a ___________ (literally, "hot water") ore deposit.
    hydrothermal 294
  228. Such ores have been deposited directly as chemical sedimentary rocks. Layered sedimentary iron ores, called ___________.
    baned iron formation 296
  229. When a body of seawater trapped in a shallow sea dries up, it deposits these minerals in _______ deposits.
    evaporites 296
  230. The currents of a coastal environment can also cause sediment sorting and selective concentration of minerals. Such deposits, mechanically concentrated by water, are called ___________.
    placers 297
  231. __________ methods are becoming increasingly sophisticated and valuable in mineral exploration.
    Remote sensing 305
  232. Perhaps the most widespread undersea mineral resource is __________.
    manganese nodules 307
  233. Overlying vegetation, soil, and rock are stripped off, the coal or other material is removed, and the waste rock and soil are dumped back as a series of _________.
    spoil banks 311
  234. The fine waste materials, or ________, that are left over may end up heaped around the processing plant to weather and wash away, much like spoil banks.
    tailings 312
  235. The _______ are those energy sources that formed from the remains of once living organisms.
    fossil fuels 316
  236. It is not a single chemical compound. __________, or ________ comprises a variety of liquid hydrocarbon compounds ( compounds made up of different proportions of the elements carbon and hydrogen).
    liquid petroleum, oil 318
  237. There are also gaseous hydrocarbons (______), of which the compound methane is the most common.
    natural gas 318
  238. Therefore, oil and natural fas are among the _________ energy sources.
  239. Most coal deposits contain significant amounts of ___________.
    coal-bed methane 325
  240. Enormous quantities of natural gas might exist in such __________; recent estimates of the amount of potentially recoverable gas in this form range from 150 to 2000 trillion cubic feet.
    geopressurized zones
  241. The process requires _________ conditions,in which oxygen is absent or nearly so, since reaction with oxygen destroys the organic matter.
    anaerobic 331
  242. Further burial, with more heat, pressure, and time, gradually dehydrates the organic matter and transforms the spongy peat into soft brown coal (_______) and then to the harder coals (________ and _________)
    lignite, bituminous, anthracite 331
  243. The conversion processes are called _________ (when the product is gaseous) and _________ (when the product is liquid fuel).
    gasification. liquefaction 333
  244. _______ us very poorly named. The rock, while always sedimentary, need not be a shale, and the hydrocarbon in it is not oil! the potential fuel in oil shale is a sometimes-waazy solid called ________, which is formed from the remains of plants, algae, and bacteria.
    oil shale, kerogen 337
  245. ________, also known as oil sands, are sedimentary rocks containing a very thick, semisolid, tarlike petroleum called ________.
    tar sands, bitumen 338
  246. _______ is the splitting apart of atomic nuclei into smaller ones, with the release of energy.
    fission 343
  247. _______ is the combing of smaller nuclei into larger ones, also releasing energy.
    fusion 343
  248. Some of the newly release neutrons can induce fission in other nearby uranium-235 in breaking up, and so the process continues in a ___________.
    chain reaction 343
  249. A _________ can maximize the production of new fuel.
    breeder reactor 344
  250. Resultant overheating of the core might lead to _________, in which the fuel and core materials would deteriorate into a molten mass that might or might not melt its way out of the containment building and thus release high levels of radiation into environment.
    core meltdown 345
  251. At some point, then, the plant must be ___________-taken out of operation, broken down, and the most radioactive parts delivered to radioactive-waste disposal sites.
    decommissioned 348
  252. Direct production of electricity using sunlight is accomplished through ________, also called simply "solar cell".
    photovoltaic cells 352
  253. Heat from the cooling magma heats any ground water circulating nearby. This is the basis for extracting ___________ on a commercial scale.
    geothermal energy 355
  254. The __________ is the rate of increase of temperature with increasing depth in the earth.
    geothermal gradient 357
  255. Where geothermal gradients are at least 40 degrees C/ kilometer, even in the absence of much subsurface water, the region can be regarded as a potential geothermal resource of the __________ type.