Igneous rocks

All of the earth's internal heat was acquired very early in its history through meteoric impact and differentiation of the core. The earth's interior loses heat to space but does not currently receive heat through any known process- True/False

False

When rock is melted within earth, typically the entire volume of rock is transformed from a solid state to a liquid- True/False

False

A sill is a. a sheetlike intrusion that lies parallel to surrounding layers of sedimentary rock b. a cooled layer of lava c. an intrusion formed within the magma chamber of a volcano d. a sheetlike intrusion that cuts across preexisting layers

a. a sheetlike intrusion that lies parallel to surrounding layers of sedimentary rock

Coarse grained diorite is most similar in mineral composition to fine grained a. andesite b. basalt c. komatiite d. rhyolite

a. andesite

As compared to aphanitic igneous rocks, phaneritic rocks are ____________. a. coarser grained b. finer grained c. more mafic d. more felsic

a. coarser grained

As compared to coarse grained igneous rocks, all fine grained igneous rocks a. cool and solidify more quickly b. cool and solidify more slowly c. solidify at higher temps d. solidify at lower temps

a. cool and solidify more quickly

Which type of magma has the greatest silica content? a. felsic b. intermediate c. mafic d. ultramafic

a. felsic

Which type of magma is produced at the coolest tempatures? a. felsic b. mafic c. intermediate d. ultramafic

a. felsic

If a body of magma becomes for felsic, its viscosity will a. increase b. decrease c. stay the same

a. increase

When magma crystallizes, ____________ are formed. a. intrusive igneous rocks b. extrusive igneous rocks c. volatiles d. pyroclastic debris

a. intrusive igneous rocks

Due to fractional crystallization and assimilation of surrounding host rock, most magmas that rise slowly through the crust evolve chemically to become a. more felsic b. more mafic c. dominated by nonsilicate minerals

a. more felsic

In Bowen's discontinuous reaction series, the first mineral to crystallize from a mafic melt is ____________. a. olivine b. plagioclase c. pyroxene d. quartz

a. olivine

Stoping by magmas occurs when ____________. a. pieces of surrounding country rock are broken off and assimilated b. the magma stops flowing and starts to solidify c. the magma becomes fully solidified to form intrusive rock d. the magma alters a thin rind of surrounding country rock

a. pieces of surrounding country rock are broken off and assimilated

An igneous rock with a mixed texture of coarse grains (phenocrysts) surrounded by fine crystals (groundmass) is termed ____________. a. porphyritic b. phaneritic c. aphanitic d. necrotic

a. porphyritic

An island volcanic arc occurs at ____________. a. the Aleutian Islands of Alaska b. the Andes Mountains c. Hawaii d. Mt. St. Helens, Washington

a. the Aleutian Islands of Alaska

Very early in Earth's history, it was so hot that the surface was likely entirely molten. a. true b. false

a. true

Most commonly, felsic igneous rocks a. contain more iron and magnesium than intermediate rocks b. are lighter in color than mafic rocks c. are darker in color than mafic rocks d. are found in oceanic crust

b. are lighter in color than mafic rocks

Coarse grained gabbro is most similar in mineral composition to fine grained a. andesite b. basalt c. komatiite d. rhyolite

b. basalt

If the volatile content of magma is increased, its viscosity will ____________. a. increase b. decrease c. stay the same

b. decrease

Pillow basalts, shown below, attain their distinctive blob-like shapes because their parent lavas do not travel far prior to solidification. This is because the parent lavas ____________. a. are completely devoid of volatiles and thus travel slowly b. erupt underwater and thus cool very quickly c. are highly felsic and thus travel slowly d. are ultramafic and thus freeze at exceptionally high temperatures

b. erupt underwater and thus cool very quickly

A majority of the melts in the Earth form through the partial melting of ultramafic mantle rock. These newly formed magmas are ____________. a. ultramafic b. mafic c. felsic d. intermediate

b. mafic

Volcanoes that do NOT occur along either present or emergent plate boundaries are associated with ____________. a. continental rifts b. mantle hot spots c. mid-ocean ridges d. subduction zones

b. mantle hot spots

When rock is partially melted, the chemistry of the melt is a. more mafic than the original chemistry of the rock b. more felsic than the original chemistry of the rock c. identical to the original chemistry of the rock d. completely unpredictable

b. more felsic than the original chemistry of the rock

If a body of magma is subjected to fractional crystallization, the rock that results is expected to be a. identical in chemical composition to the magma b. more mafic than the magma c. more felsic than the magma d. contain more black/green minerals than the source rock

b. more mafic than the magma

Bowen's continuous reaction series describes the crystallization behavior of a single mineral (with variable chemical composition), ____________. a. olivine b. plagioclase c. pyroxene d. quartz

b. plagioclase

The silicate mineral that is found in the greatest variety of igneous rocks is ____________. a. olivine b. plagioclase c. pyroxene d. quartz

b. plagioclase

A blob like igneous rock body that has cooled beneath the surface of Earth is called a a. guyot b. pluton c. lava flow d. andesite

b. pluton

Pegmatites, which occur in dikes, are unusual among shallow intrusive rocks in that they _ a. possess porphyritic texture b. possess exceptionally coarse grains c. are mineralogically identical to the extrusive rock basalt d. are glassy, cooling so rapidly that crystals do not have time to form

b. possess exceptionally coarse grains

The geotherm is the rate of change of a. pressure with depth in Earth's interior b. temp with depth in earth's interior c. temp with altitude in earth's atmosphere d. temp with latitude on earth's surface

b. temp with depth in earth's interior

A continental volcanic arc occurs at ____________. a. the Aleutian Islands of Alaska b. the Andes Mountains c. Hawaii d. Japan

b. the Andes Mountains

A famous example of hot-spot volcanism occurs at ____________. a. the Aleutian Islands of Alaska b. the Andes Mountains c. Hawaii d. Mt. St. Helens, Washington

c. Hawaii

Radioactive isotopes, differentiation of Earth's iron core, gravity-driven compression, and meteoric bombardment all caused early earth to a. glow brighter than the sun b. be much cooler than at present c. be much hotter than at present d. be much more oblong than at present

c. be much hotter than at present

All other factors being equal. intrusive rocks that form deep within earth __ than intrusive rocks that cool near the surface a. are more felsic b. contain a smaller proportion of volatiles c. cool more slowly d. cool more rapidly

c. cool more slowly

Volatiles refer to substances that a. crystallize most rapidly out of a melt b. melt immediately upon contact with a hot body of magma c. have a tendency to evaporate and are stable as gases

c. have a tendency to evaporate and are stable as gases

A volcanic neck, such as that seen at Shiprock, New Mexico (below), is a (an) ____________. a. sheet-like intrusion that lies parallel to surrounding layers of sedimentary rock b. cooled layer of lava c. intrusion formed within the magma chamber of a volcano d. sheet-like intrusion that cuts across preexisting layers

c. intrusion formed within the magma chamber of a volcano

Geologically, melts are equivalent to both ____________ and ____________. a. felsic magma; mafic magma b. felsic lava; mafic lava c. lavas; magmas d. fine-grained igneous rocks; coarse-grained igneous rocks

c. lavas; magmas

The difference between lava and magma is that a. magma is light in color and lava is dark b. magma usually has mafic composition an lava usually has felsic composition c. magma is found beneath the Earth's surface, whereas lava has reached the surface d. magma flows more quickly than lava

c. magma is found beneath the Earth's surface, whereas lava has reached the surface

The difference between magma and lava is ____________. a. magma cools more rapidly than lava b. magma is found at the surface, whereas lava is found below the surface c. magma is found beneath the surface, whereas lava is found at the surface d. There is no difference; the two terms mean the same thing.

c. magma is found beneath the surface, whereas lava is found at the surface

If a body of igneous (source) rock is subjected to partial melting, the magma that is produced is expected to be ____________. a. identical in chemical composition to the source rock b. more mafic than the source rock c. more felsic than the source rock

c. more felsic than the source rock

A volcano emits ash, which falls from the sky, settles in layers and is eventually cemented. The resultant rock is termed a. pumice b. granite c. tuff d. ignimbrite

c. tuff

Important volatiles in magmas include ____________. a. iron- and magnesium-rich minerals, such as olivine b. potassium and aluminum c. water and carbon dioxide d. trinitrotoluene and nitroglycerin

c. water and carbon dioxide

Ash and lava fragments that cascade down the sides of a volcano eventually settle and lithify to form ____________. a. basalt b. andesite c. welded tuff d. ash-fall tuff

c. welded tuff

A dike is a. a sheetlike intrusion that lies parallel to surrounding layers of sedimentary rock b. a cooled layer of lava c. an intrusion formed within the magma chamber of a volcano d. a sheetlike intrusion that cuts across preexisting layers

d. a sheetlike intrusion that cuts across preexisting layers

Igneous rocks a. are formed through the freezing of a melt b. can be produced at the surface of the earth as well as deep below the surface c. are the most common type of rocks within earth d. all of the above

d. all of the above

Obsidian a. is volcanic glass b. possesses conchoidal fracture c. typically is felsic in composition d. all of the above

d. all of the above

The formation of magma within earth is not caused by which of the following processes? a. decompression b. addition of volatiles c. transfer of heat from adjacent magma or very hot rocks d. loss of volatiles to the atmosphere

d. loss of volatiles to the atmosphere

Bombs, ash, and cinders are all examples of ____________. a. intrusive igneous rocks b. hot spots c. volatiles d. pyroclastic debris

d. pyroclastic debris

Coarse-grained granite is most similar in mineral composition to fine-grained ____________. a. andesite b. basalt c. komatiite d. rhyolite

d. rhyolite

As compared to mafic igneous rocks, all felsic igneous rocks a. cool and solidify more quickly b. cool and solidify more slowly c. solidify at higher temps d. solidify at lower temps

d. solidify at lower temps

Which type of magma has the greatest iron and magnesium content? a. felsic b. mafic c. intermediate d. ultramafic

d. ultramafic