Geology hw 4

Igneous rocks that are silica-rich with high aluminum, sodium, and potassium are _____ rocks. silicic ultramafic mafic extraterrestrial intermediate

A. Silicic

Which of the following igneous rocks exhibit aphanitic texture? granite; gabbro andesite; rhyolite andesite; diorite rhyolite; gabbro

B. andesite; rhyolite

The first plagioclase crystals to form as a hot melt cools are high in _______. iron calcium manganese carbonate lead

B. calcium

Both andesite and ___ are composed of feldspars and 30% to 50% ferromagnesian minerals. granite diorite pegmatite gabbro rhyolite

B. diorite

___ is a coarse-grained igneous rock (grains larger than 1 mm diameter) with visible grains of quartz. Gabbro Granite Basalt diorite Andesite

A. Gabbro B. Granite D. Diorite

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. Intrusive magma is cooler because it is well insulated by the surrounding rock. Intrusive magma flows onto the Earth's surface and cools very slowly, allowing many small mineral grains to grow. The extrusive magma, because it is deep below the surface, cools very slowly producing very small mineral grains.

A. The extrusive magma cools quickly so the mineral grains do not have time to grow.

Imagine two magmas that are identical in all respects (for example, same temperature, pressure, volume) except that one magma has more silica than the other. Which magma will have the higher viscosity? The magma with more silica will be more viscous. The magma with less silica will be more viscous. The magmas will have the same viscosity. There is not sufficient information to establish the relative viscosities of these magmas. Silica content does not affect magma viscosity.

A. The magma with more silica will be more viscous.

Magma for most of the andesite composite volcanoes observed along the west coast of the Americas is due to ___. an oceanic plate subducted under the asthenosphere . subduction along a divergent plate boundary rifting along a divergent plate boundary rifting along a convergent plate boundary mantle plumes

A. an oceanic plate subducted under the asthenosphere

For a rock with _____ texture a magnifying glass or microscope is needed to see individual mineral grains aphanitic porphyritic phaneritic glassy

A. aphanitic

Most of the basalt and gabbro on the ocean floor is created at mid oceanic ridges, which are also _____. divergent plate boundaries ocean - ocean convergent plate boundaries transform plate boundaries ocean - continent plate boundaries intraplate igneous areas

A. divergent plate boundaries

Fine-grained igneous rocks (grains less than 1.0 mm) that have small grains cooled rapidly and are likely to be ________. extrusive reclusive intrusive obtrusive preclusive

A. extrusive

The last minerals to crystallize on Bowen's Reaction Series result in igneous rocks with a __________ composition. felsic intermediate mafic ultramafic

A. felsic

Visible quartz and potassium feldspar grains are the main constituents in a ____________. granite gabbro basalt rhyolite

A. granite

Mineralogically and chemically equivalent rocks are ___ and ___. granite; rhyolite gabbro; basalt diorite; andesite gabbro ; granite All of the choices are correct except diorite and andesite.

A. granite; rhyolite B. gabbro; basalt C. diorite; andesite

Which magma is most likely to quench (congeal) to a natural glass? highly viscous; cools quickly highly viscous; cools slowly highly fluid; cools slowly highly fluid; cools quickly

A. highly viscous; cools quickly

A ______ is an intrusive structure that formed within the "throat" of a volcano. neck sill laccolith batholith diapir

A. neck

Consider the Bowen's reaction series. Which mineral would you expect to see as a phenocryst in a porphyritic basalt? olivine quartz orthoclase sodium-rich plagioclase

A. olivine

__________ is composed mainly of ferromagnesian minerals. Peridotite Rhyolite Andesite Granite

A. peridotite

In _____ texture the mineral grains are of roughly equal size and coarse enough to be seen without a microscope or magnifying glass phaneritic aphanitic porphyritic glassy

A. phaneritic

__________ is the dominant feldspar in basalt. Plagioclase Microcline Orthoclase Pyroxene

A. plagioclase

Which of the following igneous rocks has a pyroclastic texture? rhyolitic tuff porphyritic basalt intrusive granite andesitic lava

A. rhyolitic tuff

Imagine two magmas that are identical in all respects (for example, same chemistry, pressure, volume) except that one magma is hotter than the other. Which magma will have the higher viscosity? The hotter magma will be more viscous. The cooler magma will be more viscous. The magmas will have the same viscosity. There is not sufficient information to establish the relative viscosities of these magmas. Temperature does not affect magma viscosity.

B. The cooler magma will be more viscous

________ lava is largely restricted to narrow zones along convergent plate boundaries. Granite Andesite Rhyolite Ultramafic Carbonate

B. andesite

_________ is named for a prominent, volcanic mountain range in western South America. Basalt Andesite Pegmatite Peridotite

B. andesite

Viscosity is a property of a fluid that relates to how easily the fluid flows. A material that is viscous ___. flows easily flows less easily is always hot is always a solid is always cold

B. flows less easily

The coarse-grained equivalent of basalt is a(n) _______. andesite gabbro granite diorite rhyolite

B. gabbro

What do pumice and obsidian have in common? basaltic composition glassy texture ultramafic composition phaneritic texture

B. glassy texture

______ is the predominant igneous rock of the continents. Basalt Granite Rhyolite Gabbro Limestone

B. granite

_____ rock has two or more, distinctly different-sized populations of mineral grains aphanitic porphyritic phaneritic glassy

B. porphyritic

The sizes, shapes, and arrangements of mineral grains in an igneous rock is known as . silica content texture mineral content Bowen's reaction series

B. texture

A __________ is an open cavity in a volcanic rock that was filled by a gas bubble when the lava was still mainly liquid? porphyrocryst vesicle phenocryst xenocryst

B. vesicle

______ igneous rocks, like gabbro and basalt, are silica-deficient with high magnesium and iron. Felsic/silicic Intermediate Mafic Intrusive Extrusive

C. Mafic

Hawaii and __________ eruptions are related to intraplate igneous activity Japan Cascade Yellowstone Honduras California

C. Yellowstone

Mafic magma generated in the _______ rises to the base of the crust. continental crust outer core asthenosphere spreading ridges mantle plumes

C. asthenosphere

Igneous rocks may be either ____ if they form on or near Earth's surface, or ___ if they solidify under ground. intrusive; volcanic volcanic; extrusive extrusive; intrusive plutonic; intrusive intrusive; extrusive

C. extrusive; intrusive

The most common minerals in a granite are the _______. oxides carbonates feldspars ferromagnesians micas

C. feldspars

Ultramafic igneous rocks are composed almost entirely of ___. feldspar quartz ferromagnesian minerals calcite diamonds

C. ferromagnesian minerals

________ 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? Welded tuff sheets Basaltic lavas Granitic pegmatites Diorite plutons

C. granitic pegmatites

The melting point of a mineral generally _____ with increasing pressure (depth). does not change decreases increases becomes dependent on rock type is unknown

C. increases

To explain the great volumes of granite plutonic rocks, most geologist think that partial melting of the _______ must take place. core lower mantle lower continental crust oceanic crust asthenosphere

C. lower continental crust

Geologists regard basaltic magma (Hawaiian lava, for example) as the result of the partial melting of ultramafic rock in the _____. oceanic crust continental crust mantle outer core inner core

C. mantle

__________ is characterized by very coarse mineral grains? Obsidian Pumice Pegmatite Granite

C. pegmatite

_________ is the dominant lava erupted from volcanoes on Hawaii and Iceland. Rhyolite Andesite Peridotite Basalt

D. Basalt

___ are igneous rocks that are silica-deficient but high in iron and magnesium. Felsic Intermediate Oxide Mafic Sulfate

D. Mafic

______, a coarse-grained rock composed of pyroxene and olivine, is the most abundant ultramafic rock. Diorite Gabbro Granite Peridotite Hematite

D. Peridotite

A _______ is a tabular (thin but large area) intrusive body that is concordant (parallel to the host rock structure). dike mantle threshold sill neck

D. Sill

__ are fragments of country rock that are distinct from the body of igneous rock in which they are enclosed Clasts Chill zones Phenocrysts Xenoliths Necks

D. Xenoliths

Changing the composition of magma by incorporating surrounding host rock is known as __________. magma mixing partial melting differentiation assimilation

D. assimilation

The crust beneath the world's oceans is mafic _________. iron asthenosphere granite and rhyolite basalt and gabbro

D. basalt and gabbro

_________ has the same mineral composition as andesite? Basalt Granite Gabbro Diorite

D. diorite

_____ magma cools and consolidates without growth of mineral grains aphanitic porphyritic phaneritic glassy

D. glassy

In a porphyritic volcanic rock, which mineral grains are the last to crystallize? phenocrysts vesicles pegmatites matrix or groundmass

D. matrix or groundmass

In general, basaltic magma (Hawaiian lava, for example) is a product of ___. complete melting of the continental crust complete melting of the asthenosphere partial melting of continental crust partial melting of ultramafic rock the molten outer core

D. partial melting of ultramafic rock

Which igneous rock or magma has the lowest silica (SiO2) content? granite basalt andesite peridotite

D. peridotite

________ is thought to be common in the Earth's mantle but rare in the crust? Pumice Granite Pegmatite Peridotite

D. peridotite

A (an) __________ texture represents a single, long period of cooling and crystallization. glassy pyroclastic aphanitic phaneritic

D. phaneritic

Some basaltic magma erupts along a submarine ridge to form ____. sills dikes laccoliths pillow basalts mattress basalt

D. pillow basalts

__________ is a volcanic rock that is extremely vesicular and glassy. Obsidian Pegmatite Tuff Pumice

D. pumice

Granite and ______ are composed predominantly of feldspar and quartz. oceanic crust diorite basalt rhyolite ultramafics

D. rhyolite

On its slow journey through the crust, mafic magma evolves into intermediate magma by differentiation and assimilation of _______. mantle rocks basalt gabbro silicic rocks

D. silicic rocks

_____ rocks have coarse crystals in a fine-grained matrix. Ultramafic Granite Sill Pegmatite Porphyritic

E. Porphyritic