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2011-02-15 13:04:34

Unit 1 Geology test
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  1. Most astronomers believe
    that the universe
    came into existence as the result of a "BigBang"
  2. Most of the mass of the
    solar system is concentrated in
    the sun
  3. The solar system formed about
    4.5 billion years ago
  4. The planet closest to the sun is
    Mercury (table 1.1)
  5. Which of the following planets most closely resembles Earth in size?
    Venus (table 1.1)
  6. A planet that has ice caps composed of carbon dioide ice is
    Mars (table 1.2)
  7. Wich of the following was an important heat source for melting of the primitive earth?
    collisions of infalling particles
  8. Continental crust differs from oceanic crust in that it
    contains more light minerals than oceanic crust. (figure 1.3)
  9. Of the earth's major compositional zones, the largest is the
    mantle (figure 1.3)
  10. The earth's outer core is
    liquid (figure 1.3)
  11. The earth's core is composed mostly of
  12. The 3 most abundant elements in the earth's crust are oxygen, silicon, and
    aluminum (table 1.2)
  13. Earth's early atomosphere
    contained little or no oxygen
  14. A planet whose density reflects a significant iron content and relatively little gas is
    Venus (table 1.1)
  15. There are few fossils of the earth's earliest living organisms because
    the earliest living organisms were soft-bodied and thus did not preserve well as fossils
  16. Of the following eras of geologic time, the correct sequence from oldest to youngest is
    Paleozoic, Mesozoic, Cenozoic (figure 1.4)
  17. A scientific theory
    may be modified or completely discarded if it fails to explain new kinds of data or observations
  18. Which one of the following regions of the world had the highest average population growth rate (% per year) between 1990 and 1995
    Africa table 1.4
  19. North and Central America are projected to contain _______ percent of the world's population by the year 2025
    7.4 (figure 1.14)
  20. The term "carrying capacity" refers to
    the ability of the earth to sustain its population in reasonably healthy and comfortable conditions
  21. Each planet of the solar system is believed to have formed
    from an accumulation of dust and gas drawn together by _____.
  22. The planet having the largest diameter relative to earth is _______.
  23. The process by which simple plantlike organisms introduced free oxygen into the earth's atmosphere is called ________.
  24. The dinosaurs appeared about ___ million years ago.
  25. The means of discovering basic scientific principles is called the ________.
    scientific method
  26. Food, unlike minerals or land, is considered to be a ________ resource.
  27. On a global scale, the human population increases when its birthrate exceeds its _________.
    death rate
  28. Population growth is ________ when the number of individuals added per unit of time increases over time.
  29. _______ time is the length of time required for a population to double in size.
  30. The average worldwide population growth rate is about ____ percent per year.
  31. True or False. According to most theories of the formation of the solar system, the sun formed independently from the planets, and the planets were later captured by the sun's gravitational field.
    False. The sun and the planets formed together from a single rotating cloud of gas.
  32. True or False. The composition of a planet within the solar system is largely a function of its distance from the sun.
  33. True or False. Earth is unique among the planets of the solar system in having an abundance of surface water.
  34. True or False. The first mammals appeared on earth approximately 75 million years ago.
    False. Mammals first appeared on Earth approximately 200 million years ago.
  35. True or False. the emphasis of geology today is on the observation and description of natural processes.
    False. Rather than merely describing natural proceses, the modern science of geology seeks to explain how natural processes operate.
  36. True or False. A hypothesis is a generally accepted explanation for a set of data or observation.
    False. A hypothesis is a tentative explanation for a set of observations or data. A hypothesis that is repeatedly supported by experimentation may be elevated tot the status of a theory, which is a generally accepted explanation for a set of observation or data.
  37. True or False. About 100 million tons of waste is generated in the United States per year.
    False. About 300 million tons of waste is generated in the United States per year.
  38. True or False. The country having the highest per capita consumption of most mineral and energy resources is the United States.
  39. True or False. Concern over human disruption of natural systems is largely unjustified, since natural phenomena such as severe storms, volcanoes, and earthquakes disrupt natural systems to a greater extent the do human activities.
    False. Natural systems tend toward a balance among opposing forces, whereas human activities tend to cause or accelerate significant changes in natural systems.
  40. True or False. Every hour, the world population increases by about 1500 people.
    False. Every hour, the world population increases by about 10,000 people.
  41. The number of natually occurring chemical elements is approximately
  42. Electrons are
    negatively charged
  43. An element's chemical identity is determined by its
    atomic number
  44. Isotopes of the same element
    have different atomic mass numbers
  45. Which of the following physical properties is not a reliable guide to mineral identification in hand specimens?
  46. The atomic number of the element oxygen (O) is 8. If it gains 2 electrons to form an anion, what will be the electrical charge of the anion?
  47. Which of the following is a good example of a chemical sedimentary rock?
  48. An atom of a certain isotope of carbon has 6 protons, 6 electrons, and 8 neutrons. Its atomic mass number is
  49. In an electrically neutral atom,
    the number of protons and the number of electrons are the same
  50. Ionic bonding occurs when
    oppositely charged ions attract each other
  51. All of the following statements concerning minerals are correct except
    some minerals are produced by biological processes
  52. The 2 fundamental characteristics that distinguish a mineral from all other minerals are its
    chemical composition and crystal structure
  53. Which one of the following compounds contains 3 elements and 6 atoms?
  54. The tendency of a mineral to break apart preferentially in certain directions, depending on its crystalline structure, is known as
    cleavage (figure 2.5)
  55. The correct sequence of minerals arranged in order of increasing hardness is
    talc, calcite, quartz, corundum. (table 2.1)
  56. The most abundant group of minerals in the earth's crust is the
  57. Ferromagnesian minerals belong to the ______ group of minerals.
  58. An example of a plutonic igneous rock is
  59. All of the following are examples of clastic sedimentary rocks except
    • a. conglomerate
    • b. shale
    • c. sandstone
    • ->d. limestone
  60. Metamorphosed limeston is called
  61. An _____ is the smallest particle into which an element can be subdivided while still retaining the chemical characteristics of the element.
  62. The atomic number is the number of ______ in an atomic nucleus.
  63. The atomic _____ number is the sum of the number of protons and the number of neutrons in an atomic nucleus.
  64. An __ is an atom that has lost or gained electrons.
  65. ______ bonding occurs when the atoms of a compound share electrons.
  66. A _____ is a chemical combination of 2 or more elements, i specific proportions, having a distinctive set of physical properties.
  67. The atoms of ______ materials are arranged in regular, repeating patterns.
  68. _______ is the ability of a mineral to resist scratching.
  69. The silica ______, consisting of 4 oxygen anions surrounding a single silicon cation, is the basic building block of silicate minerals.
  70. ______ are silicates in which atoms are tightly bonded into 2-D sheets.
  71. _____ is the simplest silicate containing only silicon and oxygen.
  72. _____ are unusual among silicate in that their structures can absorb or lose water.
  73. ______ is a naturally occurring silicate melt, which may also contain suspended mineral crystals and dissolved water and gases.
  74. _____ sedimentary rocks are those formed from fragments of preexisting rocks.
  75. _______ metamorphism occurs adjacent to a cooling magma body, while metamorphism occurs on a large scale involving heat and pressure generated by mountain-building or plate-tectonic movement.
    Contact, regional
  76. True or False. Cations are negatively charged ions; anions are positively charged ions.
    False. Anions are negatively charged ions; Cations are positively charged ions.
  77. True or False. The symbols for some elements, such as Fe for iron and Pb for lead, are derived from the Latin names for these elements.
  78. True or False. Color is one of the physical properties to use in the identification of a mineral.
    False. The color of a mineral can sometimes vary from specimen to specimen due to trace impurities. Also different minerals can sometimes have the same color.
  79. True or False. Most minerals are oxides.
    False. Most minerals are silicate.
  80. True or False. The economically important minerals of many metals are sulfides.
  81. True or False. Calcite is the most abundant carbonate mineral and is and important constituent of limestone and marble.
  82. True or False. Sulfur, gold, and graphite are examples of native elements.
  83. True or False. Magmas that crystallize rapidly produce igneous rocks characterized by large mineral crystals.
    False. Magmas that crystallize rapidly typically produce fine-grained igneous rocks.
  84. True or False. Typical examples of metamorphic rocks that exhibit foliation include marble and quartzite.
    False. Examples of foliated metamorphic rocks include slate, schist and gneiss.
  85. True and False. The rock cycle is a consequence of the continually changing geologic environment.
  86. Carbonates?
    Contain one or more metals plus carbon and oxygen in the ration of 1:3
  87. Sulfates?
    Contain one or more metals plus sulfur and oxygen in the ratio of 1:4
  88. Oxides?
    Contain one or more metals plus oxygen
  89. Hydroxides?
    Contain one or more metals plus hydrogen and oxygen in the ration of 1:1
  90. Sulfides?
    Contain one or more metals plus sulfur without oxygen
  91. Halides?
    Contain a metal plus fluorin, chlorine, bromine, or iodine
  92. Native elements?
    Consist of a single element
  93. One of the first scientists to propose the hypothesis of continental drift was
    Alfred Wegener
  94. The hypothesis of continental drift was initially rejected by most scientist because
    few scientists believed it possible for the continents to move over a solid earth
  95. The lithosphere
    is thickest under the continents, thinnest beneath the oceans
  96. The asthenosphere lies entirely within
    the upper mantle (figure 3.4)
  97. The study of paleomagnetism has revealed that
    earth's magnetic field has reversed many times
  98. The origin of earth's magnetic field is probably due to
    electric currents in the fluid outer core
  99. Ocean floor rocks on both sides of an ocean ridge show
    alternating bands of normal and reverse magnetization on both sides of the ridge
  100. Relative to continental crust, ocean floor crust is
    much younger
  101. About 200 million years ago, earth's landmasses were united in a single supercontinent called
  102. The landmass that eventually split up into South America, Africa, india, Antarctica, and Australia was
    Gondwanaland (figure 3.14)
  103. New lithosphere is created at
    divergent plate boundaries
  104. The San Andreas fault is an example of
    a transform fault
  105. India
    drifted into Asia
  106. The Himalaya and Appalachian Mountains represent sites of sustained
    plate convergence
  107. Island arcs are associated with
    ocean-ocean convergences
  108. All of the following have been used to determine the rates and directions of plate movements except
    earthquake locations
  109. Hot spots
    remain stationary as lithospheric plates move over them
  110. Lithospheric plates move at an average rate of _____ per year
    2 to 3 centimeters
  111. Plate tectonic processes on earth have been active for at least
    2 billion years
  112. The ages of the volcanoes comprising the Hawaiian chain of islands is consistent with
    an east-souteast direction of movement of the PAcific Plate over a stationary mantle hot spot
  113. _____ is the study of large-scale movement and deformation of the earth's crust
  114. The solid and rigid outermost layer of the earth is called the _______
  115. _____ stress tends to squeeze an object; _____ stress tends to pull an object apart.
    Compressive, Tensile
  116. ____ is the deformation produced in a body of matter in response to stress applied to it.
  117. If a material is subjected to _____ deformation, the material will return to its original size and shape when the stress is removed.
  118. A ___ material may rupture before there is any plastic deformation.
  119. _____ temperature is the temperature above which a magnetic material loses its magnetism.
  120. The ocean floor is made up largely of the volcanic rock known as _____.
  121. A a _____ plate boundary, lithospheric plates move apart; at a ______ plate boundary, lithospheric plates move toward each other.
    divergent, convergent
  122. Laurasia and _______ are names given to the northern and southern portions of Pangea, respectively.
  123. Most of North America is part of the North American Plate; however, the part of the California to the west side of the San Andreas fault is part of the _____ plate.
  124. Excess sea floor is consumed in _____ zones.
  125. _____ cells in the asthenosphere may be driving force behind plate tectonics.
  126. The concept that rocks are constantly subject to change and that any type of rock can be transformed into another type of rock is called the __________.
    rock cycle
  127. True or False. Volcanoes and earthquakes are concentrated along the margins of lithospheric plates.
  128. True or False. The discovery of the asthenosphere proved that lithospheric plates move.
    False. The discovery of the asthenosphere did not prove that lithospheric plates move; however, its discovery made the continental drift hypothesis more plausible.
  129. True or False. The North American Plate is moving to the south with respect to the Pacific Plate.
    False. The North American Plate is moving to the west with respect to the Pacific Plate.
  130. True or False. Seafloor rocks get progressively younger the farther they are both sides of an ocean ridge.
    False. Seafloor rocks get progressively older the farther they are from both sides of an ocean ridge.
  131. True or False. Polar-wander curves prove that the magnetic poles have meandered over the earth;s surface with time.
    False. Polar-wander curves provide a means of mapping the directions in which the contents have moved with time relative to each other and the earth's stationary magnetic poles.
  132. True or False. The breakup of the supercontinent Pangea began about 200 million years ago.
  133. True or False. New lithosphere is created along divergent plate boundaries.
  134. True or False. The opposite sides of a transform fault belong to 2 different plates moving in opposite direction.
  135. True or False. Continental lithosphere is similar in density to that of the asthenosphere.
    False. Oceanic lithosphere is similar in density to that of the asthenosphere.
  136. True or False. A continent-continent collision may result in increased thickness of continental crust.
  137. Slow, gradual movement along a fault is called
  138. The point of first break on a fault during an earthquake is called the
    focus (figure 4.4)
  139. Earthquakes originate in the
  140. Earthquakes P waves
    are compressional waves
  141. Which of the following is not explained by the elastic rebound theory?
    the common occurrence of the fires in earthquake-affected communities
  142. At present, we can predict
    the regions where major earthquakes are likely to occur in the future
  143. In the United State, earthquake intensity is usually measured on the
    Modified Mercalli Scale
  144. Relative to an earthquake of magnitude 5 on the Richter magnitude scale, an earthquake of magnitude 7 releases
    900 times more energy
  145. An earthquake having a magnitude of 5-5.9 would be described as a
    damaging earthquake (table 4.2)
  146. The problem of liquefaction can be somewhat reduced by
    installing efficient underground drainage systems
  147. Tsunamis
    can travel at speeds of hundreds of miles per hour
  148. Seismic gaps represent
    "locked" sections along otherwise active faults
  149. Which of the following is an example of an earthquake precursor?
    • An increase then a decrease in the electrical resistivity of rocks
    • Changes in water levels in wells
    • Anomalous animal behavior
  150. The agency of the United States government authorized to issue warning of impending earthquakes and other hazardous geologic events is the
    U.S. Geological Survey
  151. At present, all of the following nations have government-sponsered earthquake prediction programs except
    • ->a.Mexico
    • b.United States
    • c.Japan
    • d.People's Republic of China
  152. Which one of the following states has the greatest risk of experiencing a severely damaging earthquake?
    South Carolina (figure 4.31)
  153. The phenomenon in which rocks snap back elastically to their prestress condition after an earthquake is called _________.
    elastic rebound
  154. The point on the earth's surface directly above the focus of an earthquake is called the _______.
  155. When an earthquake occurs, it releases energy in the form of ______, which are divided into body waves and surface waves.
    seismic waves
  156. _____ are body waves that involve a side to side motion of molecules of the materials through which they travel.
  157. The instrument that is used to detect the ground motions generated by earthquake is called a ________.
  158. ________ is a measure of the damaging effects of an earthquake on surface features and on humans.
  159. Earthquakes that follow the main shock are called _______.
  160. An earthquake of Richter magnitude 6 causes ____ times as much ground movement as one of Richter magnitude 4.
  161. ___________ are events that precede an earthquake and can be used to predict it occurrence.
    Precursor phenomena
  162. A method of releasing built-up strain along locked sections of faults by pumping fluid into fault zones is called _________.
    fluid injection
  163. True or False. Deep focus earthquakes are concentrated in subduction zones.
  164. True or False. When an earthquake occurs, S waves from the quake are detected all over the earth.
    False. S waves do not reach the part of the earth on the opposite side from an earthquake because the cannot travel through the liquid outer core.
  165. True or False. Are S waves travel through matter, the matter is alternately compressed and expanded.
    False. S waves are shear wave that involve a side-to-side motion of molecules as they travel through the earth. P waves involve back-and-forth vibrations or compression of molecules in the direction of wave travel.
  166. True or False. The further a receiving seismograph is from an earthquake's epicenter, the shorter the time lag between the first arrival of P waves and S waves.
    False. The farther a receiving seismograph is from an earthquake's epicenter, the greater the time lag between the first arrival of P waves and S waves.
  167. True or False. Calculation of the Richter magnitde of an earthquake is based on the maximum amplitude of seismic waves recorded on the seismogram and adjusted for the distance of a seismograph from the epicenter.
  168. True or False. Earthquakes are extremely rare events.
    False. Hundreds of thousands of earthquakes of all magnitudes occur each year although most are magnitude 5 or less. table 4.2
  169. True or False. On the Modified Mercalli Scale, an earthquake of intensity I is the most destructive.
    False. On the Modified Mercalli Scale, an earthquake of intensity XII is the most destructive.
  170. True or False. Buildings constructed on deep soil usually suffer less structural damage than those built on bedrock.
    False. Buildings constructed on deep soil usually suffer more structural damage than those built on bedrock.
  171. True or False. During the 1906 San Fransisco, 70% of the damage was due to fire rather than to ground movement.
  172. True or False. It is now possible to predict the timing and size of major earthquakes.
    False. Partly because earthquake precursors are not yet completely understood, consistently reliable earthquake predictions are at least a decade or more in the future.
  173. True or False. If you are indoors during an earthquake, run outdoors immediately.
    Fasle. Remain indoors during an earthquake, seeking protection beneath a table or desk, or in a doorway.
  174. True or False. The 1989 Lorna Prieta earthquake has increased, not reduced, the near-term likelihood of failure along the peninsular segment of the San Andreas fault.
  175. Most magmas originate in the
    upper mantle
  176. Mafic (silica-poor) lavas
    are low in viscosity and flow easily
  177. Most volcanic activity on land areas occurs
    in association with subduction zones
  178. A well-known volcano associated with a rift zone is
  179. Most volcanic rock is created at
    seafloor-spreading ridges
  180. The oclumbia Plateau is an example of a
    fissure eruption
  181. The Hawaiian peak called Mauna Loa is an example of a
    shield volcano
  182. Which of the following is not a type of pyroclastic material?
    • a. volcanic bombs
    • b. volcanic cinders
    • c. volcanic ash
    • ->d. flowing lava
  183. Volcanoes composed of pyroclastics are called
    cinder volcanoes
  184. Volcanoes of the Cascade Range are
  185. The residents of the Icelandic island of Heimacy stopped a lava flow by
    cooling the lava with water
  186. A pyroclastic outburst of a denser-than-air mixture of hot gases and fine ash is known as a
    pyroclastic flow
  187. The catastrophe of Lake Nyos, Cameroon, Africa, in 1986 was caused by
    the release of carbon dioxide
  188. Volcanic eruptions may, at least temporarily,
    • contribute to the formation of acid rain
    • decrease average global temperature
    • increase the rate of ozone depetion
  189. All of the following are possible volcanic precursors except
    • a. seismic activity
    • b. deformation of a volcano's surface
    • ->c. changes in barometric pressure
    • d. changes in the mix of gases emitted by the volcano
  190. Volcanologist
    can anticipate the likelihood of an explosive eruption
  191. Concerning responses to eruption predictions, the safest course is to
    undertake precautionary evacuations
  192. Subduction is the underlying cause of the
    volcanoes of the Cascade Range of the Pacific Northwest
  193. _____ is the volcanic, fine-grained compositional equivalent of granite.
  194. The collection of volcanoes rimming the Pacific Ocean is known as the ______.
    ring of fire
  195. A _________ has formed in the crater of Mount St. Helens.
    volcanic dome
  196. Bits of violently erupted volcanic material are collectively called ________.
  197. Stratovolcanoes are also called _______ volcanoes.
  198. A mudflow of meltwater and volcanic ash produced by a volcanic eruption is called a ______.
  199. The town of St. Pierre, on the Caribbean island of Martinique, was destroyed by a ___________ that occurred during the eruption of Mont Pelee in 1902.
    pyroclastic flow (or nuees ardentes)
  200. During the A.D. 79 eruption of Mount Vesuvius, many people were killed by the release of _________.
    toxic (or volcanic) gases
  201. A volcanic considered to be ____ is very unlikely to erupt again.
  202. A ______ is an enlarged volcanic summit crater formed by either an explosion or the collapse of a volcano.
  203. True or False. the eruption of Mount ST. Helens in 1980 made many Americans realize for the first time that they lived in areas threatened by volcanoes.
  204. True or False. Silica-rich magmas are less viscous, thinner, and flow more easily than silica- poor magmas.
    Silica-rich magmas are more viscous, thicker, and flow more sluggishly than silica-poor magmas.
  205. True or False. Most volcanoes are located over subduction zones.
  206. True or False. The most energetic pyroclastic eruptions are more typical of volcanoes with viscous lavas, because thicker lavas tend to trap more gases.
  207. True or False. Lava flows are among the most hazardous of volcanic activities because they are the least predictable of volcanic hazards.
    False. Lava flows can be hazardous; however, they are at least predictable since their flow paths can be anticipated.
  208. True or False. The violent eruptions that spew sulfur-rich gases into the atmosphere may enhance the effects of acid rain.
  209. True or False. There are an estimated 3000 to 5000 active volcanoes in the world.
    False. There are an estimated 300 to 500 active volcanoes in the world.
  210. True or False. It is possible that animals might "forsee" volcanic events and that studying their behavior might provide volcanologists with clues to impending eruptions.
  211. True or False. The major eruption of Mount Pinatubo in 1991 came as a complete surprise to volcanologists and local residents.
    False. Mount Pinatubo exhibited several volcanic precursors prior to its main eruption on 15 June 1991; these included increased seismic activity, a bulge on the volcano's summit, emissions of ash, and a sudden drop in gas output.
  212. True or False. Volcanic eruption of the Indonesian island of Krakatoa in 1883 was an example of a phreatic eruption.
  213. Waves that are compressional waves that cannot travel through the earth’s liquid outer core.
    P (primary) waves
  214. Waves that are shear waves and cannot travel through the earth’s core. Both P waves and S waves are classified as body waves, because they travel through the earth's interior.
    S (secondary) waves
  215. Waves that travel along the earth’s surface, some causing vertical ground motions and others horizontal shearing motions. Much of the structural damage during earthquakes is caused by the surface waves.
    Surface waves
  216. Earthquakes related hazards are:
    • (a) Ground shaking and fault displacement.
    • (b) Ground failures, including landslides and liquefaction. Liquefaction is a quicksand condition arising in wet soil shaken by seismic waves.
    • (c) Tsunamis, or seismic sea waves, and coastal flooding.
    • (d) Fires caused by fuel line and storage tank ruptures and electrical system damage.
  217. Most magmas originate in the upper mantle, at depths between 50 and 250 kilometers, and are typically generated
    (1) at divergent plate boundaries, (2) over subduction zones, and (3) at hot spots.
  218. What accounts for the immense volume of volcanic rocks formed at the divergent boundaries (spreading centers)?
    Fissure eruption
  219. Silica-poor, iron- and magnesium-rich magmas are low in viscosity and flow easily
    Mafic magmas
  220. Silica-rich magmas are viscous and flow sluggishly. Felsic magmas tend to trap dissolved gases, which may lead to explosive eruptions.
    • Felsic magmas
    • . Felsic magmas tend to trap dissolved gases, which may lead to explosive eruptions.Explosive eruptions are potentially more hazardous than nonexplosive (passive) eruptions.
  221. A low, flat, gently sloping volcano built from many flows of fluid, low-viscosity lava. The Hawaiian Islands are composed of shield volcanoes.
    Shield Volcano
  222. A compact, steep-sided structure built of very viscous, rhyolitic and andesitic lavas emitted from a central pipe or vent. A volcanic dome has formed in the crater of Mount St. Helens left by its 1980 explosive eruption (although the Mount St. Helens volcano as a whole is a composite volcano)
    Volcanic dome
  223. A symmetric, cone-shaped volcano formed from the accumulation of pyroclastics close to the volcanic vent.
    cinder cones
  224. Is a built of interlayered lava flows and pyroclastics. They tend to have viscous, gas-charged lavas and can erupt explosively. Most of the volcanoes in the Cascade Range of the western United States are of this type.
    composite volcano
  225. The primary source of hazards related to volcanic eruptions are the products of eruptions:
    lava flows, pyroclastic flows, lahars(volcanic mudflows), ash falls, toxic gases (mainly SO2), andphreatic eruptions.
  226. Igneous Rocks
    • Igneous rocks are formed by the solidification and crystallization of a cooling magma. Plutonic igneous rocks form from magmas that cool slowly at depth and are typically coarse-grained. Volcanic igneous rocks form at or very close to the earth’s surface, and their rapid cooling and solidification
    • usually result in fine-grained textures.
  227. Sedimentary Rocks
    Sedimentary rocks are formed from sediments at low temperatures. Clastic sedimentary rocks are formed from fragments of preexisting rocks; examples include sandstone, shale, and conglomerate. Chemical sedimentary rocks are formed by direct precipitation of minerals from solution; examples include limestone and rock salt.
  228. Metamorphic rocks
    Metamorphic rocks are formed by the recrystallization of preexisting rocks that were subjected to heat and/or pressure. Examples include marble, quartzite, slate, schist, and gneiss.
  229. Physical properties of minerals
    include color, hardness (ability to resist scratching), density (mass per unit volume), and cleavage (tendency to split along certain planes of relatively weak bonding in the crystal).
  230. The melting and subsequent cooling of the earth resulted in the formation of three main compositional zones:
    • (a) the high-density, central core, composed mainly of iron and nickel;
    • (b) the surrounding mantle, composed mainly of iron, magnesium, silicon, and oxygen; and
    • (c) a low-density, thin crust, composed mainly of oxygen and silicon.
  231. Bowan's reaction series
  232. Types of Volcanoes