This activity contains 34 questions.

	Magma is _________.   completely or partially molten material, which on cooling solidifies to form an igneous rock completely or partially molten material, which on cooling liquefies to form a lava tube an igneous rock, which on melting becomes completely or partially lava a lava fountain that completely or partially cools and solidifies to form molten rock

	The origin of magma is well understood.    True  False

	Igneous rocks that form at depth are referred to as intrusive or plutonic rocks.    True  False

	Examine this VolcanoWorld page. What is the difference between a tholeiitic basalt and an alkali basalt?   A tholeiitic basalt contains more conspicuous plagioclase and pyroxene crystals. A tholeiitic basalt contains no olivine. An alkali basalt contains potassium feldspar. An alkali basalt contains more conspicuous plagioclase and pyroxene crystals. None of the above are true.

	Identify the type of igneous rock you would expect to find at each of the indicated locations by selecting the correct response. For each item below, use the pull-down menu to select the letter that labels the correct part of the image. 5.1 mid-ocean ridge basalt A B C D 5.2 recent andesite A B C D 5.3 intraplate (hot-spot) basalt A B C D 5.4 ancient granite A B C D

	What is meant by “extrusive” and “intrusive”?   Igneous rocks that cooled at the surface (volcanic) and interior to the surface (plutonic) of the Earth, respectively. Sedimentary rocks that cooled at the surface (volcanic) and interior to the surface (plutonic) of the Earth, respectively. Metamorphic rocks that cooled at the surface (volcanic) and interior to the surface (plutonic) of the Earth, respectively. All of these.

	The most common extrusive igneous rock is granite.    True  False

	The only factor that determines the texture of an igneous rock is the amount of silica present in the magma.    True  False

	A slowly cooled magma will most likely result in a rock with which one of the following textures?   phaneritic pyroclastic glassy aphanitic porphyritic

	The large crystals in an igneous rock with a porphyritic texture are referred to as phenocrysts.    True  False

	The fine grained volcanic equivalent of granite is basalt.    True  False

	For igneous rocks, crystal size is interpreted to imply which of the following?   how the magma felt during cooling time allowed for cooling of the magma/lava temperature of the magma chemistry/composition of the magma

	Granitic rocks contain about 70 percent silica and are major constituents of the continental crust.    True  False

	As the silica content of magma increases, the viscosity decreases.    True  False

	Igneous rocks that contain substantial dark silicate minerals and calcium-rich plagioclase feldspar (but no quartz) are said to have a basaltic, or mafic, composition.    True  False

	Examine these geology class notes on igneous rocks from Georgia Perimeter College. What mineral is most likely to compose the phenocrysts in a granite porphyry?   potassium feldspar olivine quartz pyroxene muscovite mica

	According to the class notes referenced in Question 23, the term "sialic" refers to igneous rocks with a(n) __________ composition.   basaltic (mafic) granitic (felsic) intermediate none of the above

	Referring to the class notes indicated in Question 23, which one of these rock textures was created by a period of slow cooling, then uplift and rapid cooling.   phaneritic aphanitic porphyritic-phaneritic porphyritic-aphanitic none of the above

	Which one of the following rock types has an aphanitic texture?   granite basalt gabbro peridotite diorite

	Which one of the following rocks is an ultramafic?   rhyolite peridotite basalt diorite gabbro

	The intrusive equivalent of the igneous rock basalt is gabbro.    True  False

	Bowen demonstrated in his experiments that minerals crystallize from magma in a systematic fashion.    True  False

	According to Bowen's reaction series, quartz is often the last mineral to crystallize from a melt.    True  False

	The first minerals that form in a cooling magma are primarily members of the sulfide group.    True  False

	Both temperature and pressure play important roles in the formation of magma.    True  False

	Water vapor, carbon dioxide, and sulfur dioxide are the most common gases found in magma.    True  False

	Which one of the following factors is most important in determining the texture of an igneous rock?   the type of dissolved gases in the magma the rate at which the magma cools the composition of the magma the type of rock surrounding the magma the time of the year the rock forms

	The geothermal gradient __________.   is the change in temperature with depth averages 20 to 30 degrees C per kilometer in the upper crust varies with depth is all of the above

	Most basaltic magmas probably originate from partial melting of the ultramafic rock peridotite, the major constituent of the upper mantle.    True  False

	Because magma's density is greater than the surrounding rocks, it works its way to the surface over time spans from thousands to millions of years.    True  False

	"Wet" rock buried at depth has a much greater melting temperature than does "dry" rock of the same composition and under the same confining pressure.    True  False

	There is strong evidence that andesitic and granitic magmas originate from the interactions between mantle-derived basaltic magmas and the more silica-rich components of Earth's crust.    True  False

	Identify the most likely magma type at each indicated location by selecting the correct response. For each item below, use the pull-down menu to select the letter that labels the correct part of the image. 33.1 The magma here is probably most silica-rich. A B C 33.2 The magma here is intermediate in composition. A B C 33.3 The magma here is probably most rich in iron and magnesium. A B C

	Which rock and environment has the highest concentration of rare elements?   pegmatite, crystallized from a water-rich, highly-differentiated, residual magma basalt dike, crystallized and solidified in a vertical fracture at shallow depth pumice, crystallized at depth in a mass of intrusive rock peridotite, crystallized at depth in the upper mantle