1. Igneous rocks have large crystals when they A. form at shallow...

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1. Igneous rocks have large crystals when they A. form at shallow depths in Earth's crust. B. form in the presence of water. C. grow in slow cooling magma at depth. D. grow in magmas enriched in gases. 2. A finely crystalline or glassy igneous texture indicates that A. There was a lot of gas in the magma B. The rock cooled quickly C. The rock broke apart as it partially solidified D. The rock cooled slowly E. The ash and pumice were hot and became compacted 3. Match the rock names in the first row to the characteristics listed below. Granite, gabbro, andesite, basalt, rhyolite, diorite an extrusive rock with intermediate composition light colored rock with large crystals coarse grained rock with intermediate composition dark colored rock with microscopic crystals the extrusive form of granite coarse grained mafic rock 4. True or False - Felsic igneous rocks contain relatively large proportions of Ca-rich plagioclase feldspar and olivine. 5. True or False - Pyroxene is more common in mafic igneous rocks than in felsic rocks. 6. The primary source of heat in the Earth's interior is A. heat generated by collisions of materials as the planet formed. B. heat generated by collisions with meteorites and comets early in Earth's history. C. heat generated by the radioactive decay of elements in the planet's interior. D. heat from magma within layers in the mantle and crust. E. plate tectonics. 7. Which of the following is the best example of heat transfer by conduction? A. Heat is transferred by direct contact of a magma with rock B. Hot magma rises, cools, and then sinks C. Heat rises off the surface of a lava flow 8. Which conditions make it more or less likely that melting of rocks in Earth's crust will occur? A. increasing pressure more likely or less likely B. decreasing pressure -> more likely or less likely C. decreasing temperature -> more likely or less likely D. increasing temperature more likely or less likely 9. Which of the following changes in conditions represents crustal heating to cause melting of arock? Temperature Low High A. From A to B B. From B to C C. From C to D D. From A to D E. From A to C 10. Which of the following changes in conditions represents decompression melting? Temperature Low High B Co , 6. A. From A to B B. From B to A C. From B to C D. From C to B E. From D to A 11. Decompression melting is more likely to occur if a hot rock is uplifted a. rapidly b. slowly 12. True or False - The composition of an igneous rock reflects the rate of cooling of the source magma. 13. Partial melting refersto a. the formation of a more felsic magm a by precipitation of more mafic minerals b. blending or two m agmas together c. the melting of some minerals in a rock but not all 14. Partial melting of the continental crust would produce a(n) m agna a. a. felsic b. intermediate c. mafic d. ultramafic 15. Partial melting of mantle (ultram afic) rocks will generate a(n) magma. a. felsic b. intermediate c. mafic d. ultramafic 16. A viscous magma A. flows easily B. is resistant to flow 17. Which of the following causes a magma to be less viscous? A. Many silicate chains in the magma B. Higher temperature C. More felsic composition D. Lots of crystals floating in the magma 18. Which of the following igneous rocks has a texture consistent with a magma that cooled and solidified slowly at first, followed by more rapid cooling? A. small felsic crystals enclosed in large mafic ones B. small mafic crystals enclosed in large felsic ones C. large crystals like those in pegmatite D. large, early formed crystals surrounded by smaller, late formed crystals 19. Which minerals crystallize earlier from cooling magma? A. mafic B. felsic 20. Which of the following settings is most likely to have eruptions of basalt? A. Island arcs B. subduction beneath a thin continental plate C. subduction beneath a thick continental plate D. mid-ocean ridge E. continent-continent convergence zone 21. What is the composition of magma supplying volcanoes in continents above subduction zones? A. mafic B. intermediate C. felsic 22. What is the main source for the water that promotes melting in mantle rocks above subduction zones? A. Water seeps into the subduction zone from the overlying ocean B. Water is trapped in sediments that lie on top of the ocean floor of the subducting plate C. Water is expelled from the crystal structure of minerals subjected to increasing temperatures and pressures in the subducting plate 23. At which of the sites in this figure does water play role in magma generation. B D E C A. A B. B C. C D. D E. E 24. Which of the magma systems shown is most likely to generate felsic or intermediate magmas? D E C A. A B. B C. C D. D E. E 25. Which of the magma systems shown is most likely to result from decompression? D E A. A B. B C. C D. D E. E

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