CH.4 Quiz

Intermediate igneous volcanic rock is: basalt. granite. gabbro. andesite.

andesite

Granite is a coarse-grained igneous rock with about ________% SiO2. 10 30 50 70

70

What happens to temperature with increasing depth in the Earth? Temperature increases with depth at the same rate everywhere. Temperature decreases with depth at the same rate everywhere. Temperature increases faster with depth where Earth's crust is being stretched. Temperature increases faster with depth in tectonically stable regions.

Temperature increases faster with depth where Earth's crust is being stretched.

gneous rocks with crystals too small to be seen without a microscope are: coarse grained. fine grained. glassy. vesicular.

fine grained

Which of the following would be considered a rapid rate of magma ascent through the Earth's mantle and crust? 0.3 m/yr 10 m/yr 50 m/yr 50 km/yr

50 m/yr

Which of the following is not involved in classifying igneous rocks? texture group of minerals making up rock chemical composition of the rock All of the above are involved.

All of the above are involved.

Why could the early geologists in western Europe not directly observe the formation of coarse-grained igneous rocks? There weren't any igneous rocks in Europe. Coarse-grained igneous rocks form deep in the crust and are inaccessible when forming. Coarse-grained igneous rocks formed at the bottoms of deep lakes and weren't visible when forming. It was too dangerous to get close to exploding volcanoes where coarse-grained igneous rocks were forming.

Coarse-grained igneous rocks form deep in the crust and are inaccessible when forming.

Mafic igneous minerals are all rich in: Fe, Mg. Na, K. Al, Na. K, Al.

Fe,Mg

During crystallization of a magma, plagioclase feldspar becomes richer in: magnesium. calcium. sodium. iron.

Magnesium

Which of the following statements is true? Molten rock is less dense than solid rock. Molten rock is denser than solid rock. Molten rock and solid rock have the same density. There is no way to tell which is denser

Molten rock is less dense than solid rock.

Felsic igneous rocks are rich in: FeO. MgO. SiO2. CaO.

SiO2

The basis for the classification of igneous rocks based on chemical composition is __________ content. FeO Al2O3 MgO SiO2

SiO2

What is the effect of water on rock melting? Water raises the melting temperature of a rock. Water lowers the melting temperature of a rock. Water does not change the melting temperature of a rock. Water raises or lowers melting temperatures of different rock compositions.

Water lowers the melting temperature of a rock.

`Pumice is: a frothy mass of volcanic glass. identical to obsidian. an intrusive fine-grained igneous rock. a basaltic intrusive igneous rock.

a frothy mass of volcanic glass.

How did geologists discover the relationship between cooling rate and crystal size? observation of volcanic flows erupting and solidifying laboratory cooling of magmas study of granitic rocks and surrounding sedimentary rocks all of the above

all the above

Which of the following causes a decrease in melting temperature of rocks? decreasing pressure increasing water content more Felsic composition all of the above

all of the above

Which of the following igneous rocks has the same chemical composition as a diorite? andesite basalt rhyolite gabbro

andesite

Almost the entire ocean floor is comprised of which igneous rock? granite diorite rhyolite basalt

basalt

In which of the following igneous rocks would you be most likely to find the mineral (Mg,Fe)2SiO4? andesite basalt granite rhyolite

basalt

Which of the following type(s) of rock(s) crystallize at the highest temperature? basalt granite hydrothermal veins rhyolite

basalt

Great, irregular masses of coarse-grained igneous rock (the largest pluton): xenoliths. batholiths. sills. dikes.

batholiths.

Which of the following melting processes is important beneath mid-ocean ridges? decompression melting fluid-induced melting both decompression melting and fluid-induced melting neither decompression nor fluid-induced melting

both decompression melting

Fractional crystallization is the process: by which crystals formed in a cooling magma are removed from the remaining magma. by which magma is split into intrusive and extrusive as it cools. by which one-quarter of the magma crystallizes as each of four minerals. by which only a fraction of each magma ever crystallizes.

by which crystals formed in a cooling magma are removed from the remaining magma.

An igneous intrusion whose boundaries lie parallel to the layering in the surrounding country rock is considered to be: discordant. concordant. divergent. convective.

concordant

Which of the following best describes a gabbro? dark-colored, coarse-grained igneous rock dark-colored, fine-grained igneous rock light-colored, coarse-grained igneous rock light-colored, fine-grained igneous rock

dark-colored, coarse-grained igneous rock

Which of the following igneous bodies is a discordant intrusive rock? dike lava flow sill pyroclastics

dike

Pyroclastic rocks are a variety of: intrusive igneous. extrusive volcanic flows. extrusive explosive volcanics. metamorphic rocks.

extrusive volcanic flows.

Very slow cooling is required in order to grow large crystals because it takes a long time: for ions to sink to the bottom of the magma body. for ions to float to the top of the magma. for the atoms to grow from protons, neutrons, and electrons. for the ions to move through magma and "find" the correct places on a growing crystal.

for the ions to move through magma and "find" the correct places on a growing crystal.

The Palisades sill is a good illustration of the process of: partial melting. fractional crystallization. explosive volcanism. basaltic volcanism.

fractional crystallization.

Which of the following igneous rocks is the most mafic? diorite gabbro granite andesite

gabbro

While basalt is erupting to the ocean floor at mid-ocean ridges, ___________ is crystallizing in underlying magma chambers. andesite granite diorite gabbro

gabbro

The processes of magmatic stoping explain which of the following occurrences? how different rocks can arise from the same parent magma the process whereby new oceanic crust is made at spreading centers from the melting of underlying mantle how rising magma makes space for itself in the Earth's crust the formation of ash clouds with volcanic eruptions

how rising magma makes space for itself in the Earth's crust

Igneous rocks of Iceland: island arc andesites continental margin andesites mid-ocean ridge basalts continent-continent collision granites

mid-ocean ridge basalts

The coarsest-grained of all intrusive igneous rocks: granite. gabbro. diorite. pegmatite.

pegmatite

Which of the following pairs of intrusive and extrusive igneous rocks do not both have the same chemical composition? diorite and andesite granite and rhyolite peridotite and basalt All of the above pairs have the same chemical compositions.

peridotite and basalt

The dominant rock of Earth's mantle is: peridotite. granite. basalt. andesite.

peridotite.

What mineral is the most abundant in igneous rocks of intermediate composition? quartz pyroxene plagioclase feldspar olivine

plagioclase feldspar

A large igneous body formed at depth in Earth's crust: xenoliths. pyroclast. country rock. pluton.

pluton

What is the name of an igneous rock that has a mixed texture in which large crystals appear to float in a predominantly finer-grained matrix? porphyry pumice vesicular pyroclastic

poryphry

The most plentiful minerals in peridotite are: pyroxene and quartz. biotite and plagioclase feldspar. orthoclase and quartz. pyroxene and olivine.

pyroxene and olivine.

What are the most common igneous rocks found in ophiolites? andesites and diorites basalts and gabbros rhyolites and granites pumice and obsidian

rhyolites and granites

The process of magmatic differentiation explains how: rocks of varying composition can arise from the same parent magma. magma chambers form in the Earth's crust. water lowers the melting temperature of rock. all igneous rocks end up with the same composition.

rocks of varying composition can arise from the same parent magma.

Felsic, intermediate, and mafic igneous rock all are dominantly made up of ___________ minerals. carbonate sulfide oxide silicate

silicate

In what tectonic setting would you expect to find intermediate igneous rocks? mid-ocean ridges mantle plumes or "hot spots" subduction zones continental rifts

subduction zones

Most magmas form at what types of plate boundaries? mid-ocean ridges and transform faults subduction zones and transform faults mid-ocean ridges, transform faults, and subduction zones subduction zones and mid-ocean ridges

subduction zones and mid-ocean ridges

Bowen's Reaction Series summarizes: differences between intrusive and extrusive igneous rocks. the partial melting process. the fractional crystallization process. the different forms of intrusive igneous bodies.

the fractional crystallization process.

Immiscible magmas are: all basaltic. formed by partial melting. formed by fractional crystallization. two magmas that do not mix with one another.

two magmas that do not mix with one another

Which of the following properties of a magma increases with increasing silica content? melting temperature magnesium content viscosity density

viscosity

The presence of _________________ in subduction zones lowers the melting temperature and viscosity of resulting magmas over subduction zones.

water

Blocks of country rock that have fallen into magma and frozen in it as the magma crystallized: xenoliths. batholiths. sill. dike

xenoliths.