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Lava flows are typically finer grained than intrusive igneous rocks. Why? |
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 |
highly viscuous; cools quickly |
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The sizes, shapes, and arrangements of mineral grains in an igneous rock are known as _. |
texture |
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magma cools and consolidates without growth of mineral grains |
glassy |
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mineral grains are of roughly equal size and coarse enough to be seen without a microscope or magnifying glass |
phaneritic |
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rock has two or more, distinctly different sized populations of mineral grains |
porphyritic |
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a magnifying glass or microscope is needed to see individual mineral grains |
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. |
vesicle |
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Consider the Bowens reaction series. Which mineral would you expect to see as a phenocryst in a porphyritic basalt |
olivine |
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equivalent igneous rocks: |
rhyolite |
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equivalent igneous rocks: |
gabbro |
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equivalent igneous rocks: |
anderite |
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Which of the following igenous rocks exhibit aphanitic texture |
andesite, rhyolite |
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In a porphyritic volcanic rock, which mineral grains are the last to crystallize |
matrix of groundmass |
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visible quartz and potassium feldspar grains are the main constituents in a |
granite |
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Which of the following igenous rocks has a pyroclastic texture |
rhyolitic tuff |
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_ is a volcanic rock that is extremely vesicular and glassy |
pumice |
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_ is composed mainly of ferromagnesian minerals |
peridotite |
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Which of the following minerals crystallize early in bowens reaction series |
olivine |
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_ is the dominant feldspar in basalt |
plagioclase |
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which of the following are used for studying rocks with polarizing microscope |
thin sections |
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_ is characterized by very coarse mineral grains |
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 |
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 |
phaneritic |
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_ has the same mineral composition an andesite |
diorite |
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What do pumice and obsidian have in common |
glassy texture |
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Which of the following best describes an aphanitic texture |
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 |
aphanitic |
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_ is named for prominent, volcanic mountain range in western South America |
Andesite |
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_ is the dominant lava erupted from volcanoes on Hawaii and Iceland |
Basalt |
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Which igneous rock or magma has the lowest silica content |
basalt |
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_ is thought to be common in the Earth mantle but rare in the crust |
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 |
granitic pegmatites |
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last minerals to crystallize on bowens reaction series result in igneous rocks with a _ composition |
felsic |
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Changing the composition of magma by incorporating surrouding host rock is known as _ |
assimilation |
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All of the following are factors that affect the generation of magma except for |
crystal size |
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