Igneous Rocks- Chapter 4

25 July 2022
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question
Lava flows are typically finer grained than intrusive igneous rocks. Why?
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the extrusive magma cools quickly so the mineral grains do not have time to grow
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Which magma is most likely to quench (congeal) to a natural glass
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highly viscuous; cools quickly
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The sizes, shapes, and arrangements of mineral grains in an igneous rock are known as _.
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texture
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magma cools and consolidates without growth of mineral grains
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glassy
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mineral grains are of roughly equal size and coarse enough to be seen without a microscope or magnifying glass
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phaneritic
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rock has two or more, distinctly different sized populations of mineral grains
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porphyritic
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a magnifying glass or microscope is needed to see individual mineral grains
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aphanitic
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A _ is an open cavity in a volcanic rock that was filled by a gas bubble when the lava was still mainly liquid.
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vesicle
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Consider the Bowens reaction series. Which mineral would you expect to see as a phenocryst in a porphyritic basalt
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olivine
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equivalent igneous rocks: granite
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rhyolite
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equivalent igneous rocks: basalt
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gabbro
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equivalent igneous rocks: diorite
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anderite
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Which of the following igenous rocks exhibit aphanitic texture
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andesite, rhyolite
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In a porphyritic volcanic rock, which mineral grains are the last to crystallize
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matrix of groundmass
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visible quartz and potassium feldspar grains are the main constituents in a
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granite
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Which of the following igenous rocks has a pyroclastic texture
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rhyolitic tuff
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_ is a volcanic rock that is extremely vesicular and glassy
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pumice
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_ is composed mainly of ferromagnesian minerals
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peridotite
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Which of the following minerals crystallize early in bowens reaction series
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olivine
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_ is the dominant feldspar in basalt
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plagioclase
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which of the following are used for studying rocks with polarizing microscope
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thin sections
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_ is characterized by very coarse mineral grains
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pegmatite
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In which of the following igneous rocks and environments would you expect to find unusually high concentrations of rare elements such as lithium, beryllium, and boron
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pegmatite; crystallized from a water rich, highly differentiated, residual magma
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A _ teture represents a single, long period of cooling and crystallization
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phaneritic
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_ has the same mineral composition an andesite
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diorite
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What do pumice and obsidian have in common
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glassy texture
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Which of the following best describes an aphanitic texture
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the rock is crystalline; mineral grains are too small to be visible without a magnifying lens or microscope
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An _ texture would be most unlikely to occur in an extrusive igneous rock
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aphanitic
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_ is named for prominent, volcanic mountain range in western South America
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Andesite
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_ is the dominant lava erupted from volcanoes on Hawaii and Iceland
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Basalt
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Which igneous rock or magma has the lowest silica content
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basalt
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_ is thought to be common in the Earth mantle but rare in the crust
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peridotite
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_ often contain gem-quality crystals of minerals such as beryl and tourmaline and high concentrations of relatively rare elements such as lithium, boron, and beryllium
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granitic pegmatites
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last minerals to crystallize on bowens reaction series result in igneous rocks with a _ composition
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felsic
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Changing the composition of magma by incorporating surrouding host rock is known as _
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assimilation
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All of the following are factors that affect the generation of magma except for
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crystal size