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Igneous Rocks (38 points)

  1. What do you call a silicate liquid existing beneath the Earth’s surface? Magma



  1. What do you call a silicate liquid that has flowed out and along the Earth’s surface or seabed? Lava


  1. If a silicate liquid existing beneath the Earth’s surface solidifies in place, then the resulting rock is called (Intrusive)


  1. a) magma
  2. b) lava
  3. c) extrusive
  4. d) intrusive
  5. e) none of the above


  1. Solidification of a silicate liquid at the Earth’s surface or sea bed produces an

_________Extrusive________ igneous rock.


  1. The extrusive compositional equivalent of an diorite is andesite


  1. a) rhyolite
  2. b) dacite
  3. c) andesite
  4. d) basalt
  5. e) rhyodacite
  6. The extrusive compositional equivalent of gabbro is Basalt
  7. a) rhyolite
  8. b) dacite
  9. c) andesite
  10. d) basalt
  11. e) rhyodacite


  1. The extrusive compositional equivalent of granite is Rhyolite
  2. a) dacite
  3. b) rhyolite
  4. c) rhyodacite
  5. d) basalt
  6. e) andesite


  1. Can you see the minerals in phaneritic textured igneous rock with the naked eye? Yes or No . (YES)



  1. Can you see individual crystals in an aphanitic textured rock? Yes or No. (NO)


  1. The texture of an igneous rock composed of large grains visible with the naked eye

surrounded by smaller grains that can’t be seen with the naked eye is called aphanitic


  1. a) porphyroblastic
  2. b) porphyroclastic
  3. c) phaneritic
  4. d) porphyritic
  5. e) aphanitic


  1. There are two terms commonly used for fragmental material erupted from a volcano? Pickthese terms out of the following list Tephra and Proclasts


  1. a) tephra
  2. b) fragmentopyro
  3. c) pyrolite
  4. d) pyrofragmental
  5. e) pyroclasts


  1. Tephra that is larger than 64 mm is called bombs or blocks
  2. a) ash
  3. b) lapilli
  4. c) tuff
  5. d) bombs or blocks
  6. e) none of the above


  1. Pyroclastic rock composed mostly of material that is between 2 and 64 mm in size is called lapilli


  1. a) tuff breccia
  2. b) lapilli
  3. c) tuff
  4. d) blocks
  5. e) lapilli tuff
  6. Pyroclastic material that is less than 2 mm in size is called ash
  7. a) ash
  8. b) tuff
  9. c) volcanic breccia
  10. d) ash breccia
  11. e) lapilli tuff


  1. Pyroclasts between 2 and 64 mm in size would be called lapilli


  1. a) ash
  2. b) volcanic breccia
  3. c) agglomerate
  4. d) lapilli tuff
  5. e) lapilli


  1. A glassy rock derived from magma of silicic composition and containing many holes due tovisiculation is called scoria


  1. a) scoria
  2. b) pumice
  3. c) rhyolite
  4. d) andesite
  5. e) none of the above



  1. When a volcano erupts it throws into the atmosphere an eruptive column of particles andvery hot gas. This column will eventually collapse and the gas charged mixture will movedown the flanks of the volcano at high speeds as a pyroclastic flow


  1. a) an air fall
  2. b) a pyroclastic flow
  3. c) a turbidity current
  4. d) a lapilli tuff
  5. e) volcanic breccia



  1. With a loss of momentum the mixture of hot gases and particles described in question

will cease to move resulting in the deposition of a


  1. a) a columnar jointed flow
  2. b) ignimbrite
  3. c) pillow lava
  4. d) graded bed
  5. e) debris flow


  1. In the following list which describes a sequence going from high to low silica (SiO2)

silicic, mafic, intermediate, ultramafic


  1. a) ultramafic, mafic, intermediate, silicic
  2. b) silicic, mafic, intermediate, ultramafic
  3. c) silicic, intermediate, mafic, ultramafic
  4. d) ultramafic, Intermediate, silicic, mafic
  5. e) mafic, intermediate, ultramafic, silicic



  1. Are dikes discordant or concordant layering in country rocks? discordant


  1. A pluton is a body of magma or its _______________ equivalent.




  1. The exposed surface area of a stock is less than that for a batholith. What is the criticalvalue for exposed surface area separating these two common types of igneous rock bodies? 100 km2


  1. a) 1 km2
  2. b) 10 km2
  3. c) 100 km2
  4. d) 1000 km2
  5. e) None of the above


  1. The diameter of a crater is less than that for a caldera. What is the critical diameter that allows a caldera to be distinguished from a crater?


  1. a) 0.1 km
  2. b) 1 km
  3. c) 2 km
  4. d) 10 km
  5. e) None on the above


  1. Shield volcanoes always erupt voluminous quantities of


  1. a) rhyolite
  2. b) andesite
  3. c) basalt
  4. d) dacite
  5. e) rhyodacite


  1. What following term describes sub-aerial lava flows erupted in the Hawaiian Islands? Notethere may be more than one answer. pahoehoe and pillow lava


  1. a) pahoehoe
  2. b) aa
  3. c) pillow lava
  4. d) tuff
  5. e) agglomerate


  1. Are cinder cones generally larger or smaller than shield or composite volcanoes?


  1. Composite or stratovolcanoes are steep sided and are composed of ___hardened lava______ and

__volcanic ash________ material?






  1. Which of the following describes a unique kind of structure that is the result of lava coolingto form six-sided columns


  1. a) AC joints
  2. b) extensional joints
  3. c) pressure-release joints
  4. d) columnar joints
  5. e) exfoliation joints


  1. Pillow lava is erupted beneath _________ or ________.
  2. Pressure-release melting is a process that is thought to dominate beneath


  1. a) transform faults
  2. b) island arcs
  3. c) conservative margins
  4. d) mid-ocean ridges
  5. e) none of the above


  1. Dehydration reactions and the introduction of water to the mantle play an important role inthe production of ______________ beneath volcanic arcs.


  1. Partially melting mantle rock produces a liquid with a _____________ composition.


  1. In the following list, what mineral is not included in the Discontinuous Reaction Series?


  1. a) biotite
  2. b) pyroxene
  3. c) amphibole
  4. d) olivine
  5. e) none of the above


  1. When a basaltic liquid first starts to crystallize the first mineral in the Discontinuous

Reaction Series to form is


  1. a) Ca-rich plagioclase
  2. b) intermediate plagioclase
  3. c) Na-rich plagioclase
  4. d) K-feldspar
  5. e) olivine


  1. When a basaltic liquid first starts to crystallize the first mineral in the Continuous ReactionSeries to form is


  1. a) olivine
  2. b) pyroxene
  3. c) Ca-rich plagioclase
  4. d) Na-rich plagioclase
  5. e) K-feldspar


  1. The last minerals to crystallize from a basaltic liquid in which crystal settling has played arole would be


  1. a) olivine & pyroxene
  2. b) Ca-rich plagioclase & pyroxene
  3. c) amphibole & intermediate plagioclase
  4. d) biotite & Na-rich plagioclase
  5. e) quartz & K-feldspar


  1. Basaltic magma can produce intermediate to silicic magma and lava through a variety of processes. List below 1 such process.


  1. Below is a tracing from an extrusive igneous rock. Note the description of the gray

material, and that the large crystals are visible with the naked eye. Please fill in the missinglabels for the names of each of these two types of materials (2 points)


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