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Geology 1 Questions for Chapter 4 1) Lava flows are typically finer ...

Geology 1 Questions for Chapter 4 1) Lava flows are typically finer ...

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13) Which of the following igneous rocks exhibit aphanitic texture?<br />

A) granite; gabbro<br />

B) andesite; rhyolite<br />

C) andesite; diorite<br />

D) rhyolite; gabbro<br />

14) In a porphyritic volcanic rock, which mineral grains <strong>are</strong> the last to crystallize?<br />

A) phenocrysts<br />

B) vesicles<br />

C) pegmatites<br />

D) matrix or groundmass<br />

The correct answer is 'D'.<br />

Phenocrysts <strong>are</strong> the first<br />

minerals to crystallize.<br />

15) Visible quartz and potassium feldspar grains <strong>are</strong> the main constituents in a ________.<br />

A) granite<br />

B) gabbro<br />

C) basalt<br />

D) rhyolite<br />

16) Which of the following igneous rocks has a pyroclastic texture?<br />

A) rhyolitic tuff<br />

B) porphyritic basalt<br />

C) intrusive granite<br />

D) andesitic lava<br />

17) ________ is a volcanic rock that is extremely vesicular and glassy.<br />

A) Obsidian<br />

B) Pegmatite<br />

C) Tuff<br />

D) Pumice<br />

18) ________ is composed mainly of ferromagnesian minerals.<br />

A) Peridotite<br />

B) Rhyolite<br />

C) Andesite<br />

D) Granite<br />

19) Which of the following minerals crystallize early in Bowen's reaction series?<br />

A) biotite<br />

B) quartz<br />

C) olivine<br />

D) muscovite<br />

20) ________ is the dominant feldspar in basalt.<br />

A) Plagioclase<br />

B) Microcline<br />

C) Orthoclase<br />

D) Pyroxene<br />

21) Which of the following <strong>are</strong> used <strong>for</strong> studying rocks with a polarizing microscope?<br />

A) polished cubes<br />

B) broken chips<br />

C) thin sections<br />

D) grain karats

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