Geo Midterm #2

Which of the following statements accurately describes a property that is NOT useful in identifying quartz? Select one: a. Color, because quartz can be many different colors. b. Fracture, because quartz does not have fracture. c. Hardness, because quartz is softer than most minerals in Mohs scale. d. Crystal habit, because quartz has a fibrous crystal habit.

a. Color, because quartz can be many different colors.

How does subduction trigger melting? Select one: a. Flux melting of the asthenosphere above the subducting slab creates a rising melt. b. The downgoing slab melts as it reaches hotter temperatures deep in the Earth. c. The overriding slab insulates the subducting slab, increasing temperature and causing melting. d. The subducting slab is made of felsic minerals, and therefore melts at lower temperatures.

a. Flux melting of the asthenosphere above the subducting slab creates a rising melt.

Which of the following locations could not possibly be part of a shield? Select one: a. Hawaii b. Canada c. Northern Europe d. Siberia

a. Hawaii

If you find graywacke in the place where it formed, you know you are looking at an ancient: Select one: a. avalanche on a submarine slope. b. sand dune. c. swamp. d. alluvial fan.

a. avalanche on a submarine slope.

A black, fine-grained tabular intrusion between two layers of horizontal sedimentary rock must logically be a Select one: a. basaltic sill. b. granitic sill. c. basaltic dike. d. granitic dike.

a. basaltic sill.

Identify the FALSE statement. Magma moves upward toward the Earth's surface Select one: a. because it's less dense than the surrounding rock. b. slowly, working its way up through cracks and narrow conduits. c. more quickly as it cools and therefore becomes less viscous. d. because the weight of overlying rock creates pressure that squeezes it up.

a. because it's less dense than the surrounding rock.

A nonmarine clastic sedimentary rock composed of angular pebble-sized fragments surrounded by matrix is: Select one: a. breccia. b. conglomerate. c. turbidite. d. arkose.

a. breccia.

Which of the following rock types does not contain the mineral calcite? Select one: a. chert b. fossiliferous limestone c. chalk d. micrite

a. chert

Intrusive igneous rocks Select one: a. cool slowly and are coarse-grained. b. are fine-grained because they cooled slowly. c. are never seen by humans because they form deep in the Earth and are never exposed at the surface. d. are rocks like basalt, andesite, and rhyolite.

a. cool slowly and are coarse-grained.

Identify the false statement. Pegmatites Select one: a. have intruded at great depth and cooled very slowly. b. can contain crystals up to tens of centimeters across. c. occur in tabular intrusions called pegmatite dikes. d. are an igneous rock type, distinguished by their unusual grain size.

a. have intruded at great depth and cooled very slowly.

Which of the following rocks is classified as nonfoliated? Select one: a. hornfels b. phyllite c. slate d. schist

a. hornfels

Normal stress: Select one: a. is a push (compression) or pull (tension) perpendicular to a surface. b. is the reason a balloon collapses when you take it to the bottom of a pool. c. occurs when rocks move sideways relative to each other. d. is a compression exerted equally from all sides.

a. is a push (compression) or pull (tension) perpendicular to a surface.

Quartzite: Select one: a. is basically a solid mass of interlocking quartz grains. b. breaks around the separate grains of quartz that make it up. c. is always either white or gray. d. always shows strong compositional banding.

a. is basically a solid mass of interlocking quartz grains.

Which of the following is NOT a mineral? Select one: a. oil, because it's a liquid, not a solid b. salt, because it's not crystalline c. a gold nugget, because it's a native metal d. pyrite, because it's a chemical compound

a. oil, because it's a liquid, not a solid

An unknown mineral scratches glass, has only average specific gravity, and shows no cleavage but does show conchoidal fracture. Which of the following could it be? Select one: a. quartz b. talc c. halite d. mica

a. quartz

As sediment is transported downstream, away from its point of origin, the particles become: Select one: a. smaller. b. more angular. c. poorly sorted. d. dominantly feldspar.

a. smaller.

When you scrape a mineral along a ceramic plate to observe the color of its powder, you are checking the physical property known as: Select one: a. streak. b. luster. c. cleavage. d. specific gravity.

a. streak.

"Wet" igneous rock melts at a lower temperature than the "dry" version of that same rock because Select one: a. the addition of volatiles in "wet" rocks lowers their melting temperature. b. they occur on the sea floor, where temperatures are already cold. c. "dry" igneous rocks are made of more felsic minerals. d. "wet" igneous rocks form at shallower depth in the Earth.

a. the addition of volatiles in "wet" rocks lowers their melting temperature.

Metamorphic aureoles typically contain nonfoliated rock like hornfels because: Select one: a. they form adjacent to an intruding pluton, which provides heat for metamorphism. b. they form as a consequence of shearing without a subsequent change in temperature or pressure. c. compressional forces associated with mountain building provide the necessary pressure to create hornfels. d. they form at shallow burial depths (less than 8 km).

a. they form adjacent to an intruding pluton, which provides heat for metamorphism.

Which statement is FALSE? Select one: a. Both chert and limestone may have either chemical or biochemical origin. b. Flint, jasper, agate, and petrified wood are all varieties of the siliceous rock travertine. c. Gypsum and halite are evaporite minerals. d. Chemical sedimentary rocks are crystalline in texture.

b. Flint, jasper, agate, and petrified wood are all varieties of the siliceous rock travertine.

Identify the FALSE statement: Select one: a. Crystals can be a variety of geometric shapes, including cubes, trapezoids, pyramids, octahedrons, hexagons, columns, blades, and needles. b. Negative ions are called cations and have more protons than electrons; positive ions are anions and have more electrons than protons. c. The faces of a crystal need not be the same size throughout the crystal, but the angle of intersection between comparable faces is the same throughout. d. There is an angle of 120 degrees between each crystal face of the hexagonal column of a quartz crystal

b. Negative ions are called cations and have more protons than electrons; positive ions are anions and have more electrons than protons.

Which of the following statements is TRUE? Select one: a. Conglomerates consist of a single grain size. b. Pieces of broken rock produced by physical weathering are collectively called clasts or detritus. c. A well-sorted clastic rock is made up of different-sized particles. d. An immature clastic rock has well-sorted, resistant grains.

b. Pieces of broken rock produced by physical weathering are collectively called clasts or detritus.

An igneous rock has a medium-gray, fine-grained groundmass with large crystals of plagioclase. Which of the following statements about it is false? Select one: a. It could logically be porphyritic andesite. b. The lava flow that produced it got quenched in ocean water. c. The plagioclase crystals are called phenocrysts. d. It began to crystallize at depth from intermediate-composition magma, then rose to the surface and became a lava flow.

b. The lava flow that produced it got quenched in ocean water.

Bowen's Reaction Series Select one: a. shows that minerals crystallize in a random order, with no particular pattern involved. b. allows a geologist to predict what minerals will be found in a given igneous rock. c. is an attempt to explain the logic of formation of sedimentary rocks. d. explains why some compounds use ionic bonds and others have covalent bonding.

b. allows a geologist to predict what minerals will be found in a given igneous rock.

Which of the following statements is FALSE? Shields: Select one: a. are composed of the oldest rock on Earth. b. are composed of extensive areas of sedimentary layers laid down on lava flows. c. are composed of rocks that were metamorphosed during Precambrian mountain-building events. d. make up large areas of Canada, northern Europe, and South America.

b. are composed of extensive areas of sedimentary layers laid down on lava flows.

Identify the FALSE statement. Recrystallization: Select one: a. occurs because thermal energy causes atoms to vibrate rapidly, breaking existing chemical bonds. b. changes the mineralogical composition of the protolith. c. changes the texture (shape and size) of the grains. d. occurs when atoms migrate to new positions on the crystal lattice where they are more stable under the hotter conditions.

b. changes the mineralogical composition of the protolith

What type of foliation does slate, a common material used for roof shingles, exhibit? Select one: a. banding b. cleavage c. schistosity d. metamorphic differentiation

b. cleavage

Choose the listing that shows the rocks in increasing degrees of metamorphism (i.e., from lower to higher grade). Select one: a. migmatite, flattened-clast conglomerate, gneiss with mica, gneiss without mica b. flattened-clast conglomerate, gneiss with mica, gneiss without mica, migmatite c. gneiss with no mica, flattened-clast conglomerate, gneiss with mica, migmatite d. gneiss with no mica, gneiss with mica, migmatite, flattened-clast conglomerate

b. flattened-clast conglomerate, gneiss with mica, gneiss without mica, migmatite

Which of the following is NOT one of the classification terms used to sort metamorphic rocks based on their chemical composition? Select one: a. quartzo-feldspathic (rich in quartz and feldspar) b. glaucophanitic (rich in glaucophane) c. calcareous (rich in calcite) d. mafic (rich in iron and magnesium)

b. glaucophanitic (rich in glaucophane)

Granite Select one: a. is an extrusive igneous rock. b. is felsic in composition. c. logically could be found in a lava flow. d. is the coarse-grained equivalent of andesite.

b. is felsic in composition.

What is the protolith of marble? Select one: a. quartz sandstone b. limestone c. phyllite d. gypsum

b. limestone

Which of the following lists accurately describes grain size increasing from smallest to largest? Select one: a. sand, silt, pebbles b. mud, silt, sand c. silt, mud, sand d. sand, cobbles, pebbles

b. mud, silt, sand

Which of the following is a mineral? Select one: a. amber (tree sap) b. oyster shell (CaCO3) c. sugar (formula C6H12O6) d. glass

b. oyster shell (CaCO3)

After an explosive volcanic eruption on an island, the surrounding sea is full of light-gray floating rock. What must it be? Select one: a. rhyolite b. pumice c. obsidian d. basalt

b. pumice

A clastic sedimentary rock with clay and silt-sized grains that breaks in thin sheets is called: Select one: a. mudstone. b. shale. c. siltstone. d. graywacke.

b. shale.

Which of the following groups of silicate minerals exhibits a single strong cleavage in one direction? Select one: a. framework silicates b. sheet silicates c. independent tetrahedra silicates d. single-chain silicates

b. sheet silicates

Which of the following statements is false? Volatiles that come out of the Earth as volcanic products Select one: a. were dissolved in the molten rock and released as the surrounding pressure lessened. b. usually consist of 50% sulfur dioxide. c. include water, carbon dioxide, nitrogen, hydrogen, and sulfur dioxide. d. contributed to forming Earth's atmosphere and oceans.

b. usually consist of 50% sulfur dioxide.

Which of the following statements is TRUE? Select one: a. Hydrogen has an atomic mass of 1. b. An isotope of an element has the same atomic mass, but different atomic number. c. Helium has an atomic number of 2. d. The atomic mass of an element is approximately equal to the number of protons in an atom of that element.

c. Helium has an atomic number of 2.

Which of the following does NOT describe a change induced on protolith rocks due to mountain building as a result of convergent-margin tectonics and continental collision? Select one: a. Surface rock is sent to great depths beneath the new mountain belt. b. The once surface rock heats up due to igneous activity and the geothermal gradient. c. Hot magma rising beneath the converging continents heats seawater, which then rises through the crust to react with the surface rocks. d. Compression and shearing metamorphose the once surface rock.

c. Hot magma rising beneath the converging continents heats seawater, which then rises through the crust to react with the surface rocks.

Which of the following statements about metamorphic rocks and their characteristic environments is TRUE? Select one: a. Gneiss is found in metamorphic aureoles surrounding plutons. b. Mylonites are found along convergent-plate boundaries where magma is rising. c. Slate, phyllite, schist, and gneiss are found in areas of continental collision. d. Blueschists are found in the mid-ocean ridge.

c. Slate, phyllite, schist, and gneiss are found in areas of continental collision.

What are vesicles? Select one: a. pieces of wall rock broken off by intruding magma b. large crystals floating in a fine-grained groundmass c. air pockets or bubbles frozen in igneous rocks as gas escaped during cooling d. horizontal igneous intrusions

c. air pockets or bubbles frozen in igneous rocks as gas escaped during cooling

Which of the following statements is FALSE? Crystals: Select one: a. have an orderly internal arrangement of atoms arranged in a lattice pattern. b. grow outward from a seed. c. are formed by the high-temperature, extremely rapid process known as solid-state diffusion. d. display symmetry.

c. are formed by the high-temperature, extremely rapid process known as solid-state diffusion.

Pillow basalts Select one: a. occur in tabular intrusions called dikes. b. are composed of felsic lava. c. are formed in a submarine environment. d. contain large bulbous crystals that cool slowly.

c. are formed in a submarine environment.

Rocks formed dominantly from the calcium carbonate shells of marine organisms are classified as _____ and called _____. Select one: a. clastic; arkose b. organic; coal c. biochemical; limestone d. chemical; travertine

c. biochemical; limestone

Which of the following statements is FALSE? A metamorphic rock: Select one: a. may be composed of different minerals than its protolith. b. may develop a texture of interlocking grains. c. cannot be formed below 1200 degrees C. d. may have preferred mineral orientation caused by differential stress.

c. cannot be formed below 1200 degrees C.

Identify the FALSE statement. Hydrothermal fluids: Select one: a. may consist of hot water, steam, and supercritical fluid. b. are chemically active solutions, not pure water. c. change a rock's chemical composition, a process known as exhumation. d. can be derived from groundwater or magma, or can be the product of metamorphic reactions.

c. change a rock's chemical composition, a process known as exhumation.

The tendency of a mineral to break and produce smooth, curving shell-shaped surfaces is termed: Select one: a. luster. b. perfect cleavage. c. conchoidal fracture. d. streak.

c. conchoidal fracture.

Which is not a tectonic setting for igneous activity? Select one: a. hot spots b. continental rifts c. continental transform fault zones d. volcanic arcs bordering ocean trenches

c. continental transform fault zones

Symmetrical ripple marks: Select one: a. suggest you're looking at an old lake bottom. b. are parallel to the current direction that created them. c. could suggest an ancient coastline. d. are a sure sign the area had periodic drought.

c. could suggest an ancient coastline.

There are two physical properties of minerals that both result in smooth, flat surfaces with specific angles between them. The first property is externally visible and is the result of how the mineral forms; the second is inherently internal and is the result of breaking a sample of the mineral. These properties are called: Select one: a. hardness and cleavage. b. cleavage and hardness. c. crystal habit and cleavage. d. cleavage and crystal habit.

c. crystal habit and cleavage.

Identify the false statement. Early Earth had numerous heat sources for igneous activity, including Select one: a. conversion of the kinetic energy of meteorite impact to heat energy. b. conversion of the kinetic energy of iron alloy sinking toward Earth's center to heat energy. c. decay of all of its radioactive elements; almost none remain today. d. conversion of the kinetic energy of colliding planetesimals to heat energy.

c. decay of all of its radioactive elements; almost none remain today.

Bowen's Reaction Series Select one: a. shows the sequence in which different sulfate minerals form during the progressive cooling of a melt. b. creates a progressively more mafic melt. c. has a continuous track in which there is observed a progressive change from calcium-rich to sodium-rich plagioclase. d. was established by laboratory experiments in which mafic melt was quenched in mercury.

c. has a continuous track in which there is observed a progressive change from calcium-rich to sodium-rich plagioclase.

Which of the following statements is FALSE? Formation of table salt: Select one: a. is, in mineralogic terms, formation of the halide mineral halite. b. takes place when a solution has become saturated. c. is an example of solidification of a melt. d. results in cubic crystals.

c. is an example of solidification of a melt.

Identify the false statement. Large igneous provinces (LIPs) Select one: a. are places where huge amounts of mafic magma have been erupted or intruded. b. represent special events in Earth's history that may have been caused by superplume activity. c. occur only along continental margins. d. may have profound impacts on the environment, including land, ocean, and atmospheric processes.

c. occur only along continental margins.

Which of the following is not an intrusive igneous structure? Select one: a. batholiths b. laccolith c. pillow lava d. sill

c. pillow lava

Which of the following statements is FALSE? Retrograde metamorphism: Select one: a. may happen as uplift and erosion bring rock closer to Earth's surface. b. requires the addition of hot water to replace water driven off during prograde metamorphism. c. requires very high pressures but needs only low temperatures to occur. d. happens under conditions of decreasing temperature and pressure.

c. requires very high pressures but needs only low temperatures to occur.

Which of the following sedimentary structures indicates that the sediments were deposited in a moving fluid? Select one: a. mudcracks b. fossil footprints c. ripple marks d. laminations

c. ripple marks

Which is NOT a common process by which metamorphic rocks are formed? Select one: a. pressure solution b. plastic deformation c. schistosity d. recrystallization

c. schistosity

Formation of a clastic sedimentary rock involves five stages. Which of the following describes erosion? Select one: a. disintegration of bedrock into separate particles b. compaction and cementation of loose particles to form solid rock c. separation of rock or regolith from its substrate d. process by which particles settle out of transport medium

c. separation of rock or regolith from its substrate

Flint was prized in early human cultures because: Select one: a. large outcrops of them often contained caves to live in. b. they are translucent minerals and were useful for windows. c. they broke with conchoidal fracture and thus made good cutting tools. d. they dissolved in water readily, contributing minerals that made healthy drinking water.

c. they broke with conchoidal fracture and thus made good cutting tools.

Which is NOT a physical property commonly used in the lab or field to identify minerals? Select one: a. color b. specific gravity c. luster d. X-ray diffraction

d. X-ray diffraction

Identify the FALSE statement. Silicates: Select one: a. have the silicon-oxygen tetrahedron as their structural unit. b. are a major component of continental crust. c. are classified on the basis of how the tetrahedrons join and share oxygen atoms. d. are a large category of minerals and include the common minerals calcite and dolomite.

d. are a large category of minerals and include the common minerals calcite and dolomite.

Which of the following statements is false? Igneous rocks Select one: a. form from the cooling and crystallization of either lava or magma. b. form in great quantity along the mid-ocean ridge. c. were the first rocks to exist on Earth. d. are coarse-grained if they cool extrusively.

d. are coarse-grained if they cool extrusively.

Identify the FALSE statement. The sediments in a subsiding sedimentary basin: Select one: a. experience increased pressure and temperature due to the weight of the overburden and the geothermal gradient. b. undergo diagenetic changes when they're at shallow depth. c. lose any oil they might contain because metamorphic conditions destroy organic molecules present. d. become high-grade foliated metamorphic rocks at depth.

d. become high-grade foliated metamorphic rocks at depth.

Geologists find evidence of bioturbation in an area of sedimentary rock. This means they must be looking at: Select one: a. deep-marine deposits rich in broken-shell material. b. the forest beds at the mouth of a major river. c. a submarine fan with deep canyons cut in it. d. bedding layers that have been churned by burrowing creatures like worms and clams.

d. bedding layers that have been churned by burrowing creatures like worms and clams.

Calcite and aragonite minerals that constitute clam shells are examples of which method of mineral formation? Select one: a. solidification of a melt b. precipitation from a solution c. solid-state diffusion d. biomineralization

d. biomineralization

Magmas have a variety of chemical compositions because of all of the following except Select one: a. they come from a variety of source rocks. b. the rocks that melt to make magma are composed of many minerals, not all of which melt under the same conditions. c. the magma's heat can melt rock from the walls of the magma chamber. d. different magmas formed in different locations are isolated and don't mix.

d. different magmas formed in different locations are isolated and don't mix.

Which of the following statements is false? Mafic minerals Select one: a. crystallize at a higher temperature than do silicic minerals. b. are rich in iron and magnesium. c. typically crystallize first out of a melt. d. form rhyolite and granite.

d. form rhyolite and granite.

Which of the following terms has nothing to do with intrusive igneous activity? Select one: a. pluton b. batholith c. diapir d. hyaloclastite

d. hyaloclastite

Which of the following is NOT one of the major classes of sedimentary rocks? Select one: a. clastic b. biochemical c. chemical d. intrusive

d. intrusive

Which of the following statements is FALSE?. Mylonite: Select one: a. forms by recrystallization in a fault zone. b. is produced by shear stress on softened rock. c. has pronounced foliation parallel to the direction of faulting. d. is a product of gneiss melting to produce felsic magma and solid mafic rock.

d. is a product of gneiss melting to produce felsic magma and solid mafic rock.

Which of the following statements is false? Felsic (or silicic) magma Select one: a. crystallizes at the lowest temperatures. b. has about 70% silica and little magnesium and iron. c. is likely to form light tan, pink, or maroon rocks. d. is less viscous than mafic magma.

d. is less viscous than mafic magma.

Which of the following statements is FALSE? Extremely high heat of metamorphism: Select one: a. causes mica to react and become feldspar or some other water-free mineral. b. drives off water, causing high-grade metamorphic rocks to be drier than low grade. c. is necessary to form migmatite. d. is necessary to elongate the large clasts in conglomerate to make flattened-clast conglomerate (metaconglomerate).

d. is necessary to elongate the large clasts in conglomerate to make flattened-clast conglomerate (metaconglomerate).

Identify the false statement. Hot solid rock in the Earth Select one: a. may be even hotter than surface lava because of the pressure of overlying rock. b. may melt if volatiles such as water and carbon dioxide are added. c. may melt if heat is transferred to it from hot mantle rock rising up into the crust. d. maintains uniform composition as it melts and becomes magma.

d. maintains uniform composition as it melts and becomes magma.

Which of the following features is a bed-surface marker, meaning it appears on the surface of a bed due to events during or soon after sediment deposition? Select one: a. laminations b. cross beds c. graded bedding d. mudcracks

d. mudcracks

Which of the following statements is false? Volcanic arcs Select one: a. form where subduction takes place. b. are long, curving mountain chains adjacent to deep-ocean trenches. c. can be continental or island-related. d. occur at divergent-plate boundaries.

d. occur at divergent-plate boundaries.

The organic sedimentary rock that is composed of mud-sized particles and partially decayed organic matter derived from plankton and algae remains is: Select one: a. coal. b. fossiliferous limestone. c. chert. d. oil shale.

d. oil shale.

Which of the following processes is associated with the formation of travertine? Select one: a. deposition b. lithification c. compaction d. precipitation

d. precipitation

Which of the following statements is FALSE? Shock metamorphism: Select one: a. involves high temperatures and compressional stress. b. can be caused by meteorite impact. c. causes quartz to recrystallize into coesite. d. probably hasn't happened on the Moon because no products of shock metamorphism have been found in Moon regolith.

d. probably hasn't happened on the Moon because no products of shock metamorphism have been found in Moon regolith.

Which of the following words could not be used to describe portions of a rock with a porphyritic texture? Select one: a. groundmass b. phenocryst c. plagioclase d. pyroclastic

d. pyroclastic

Sedimentary rocks can form by each of the following processes EXCEPT: Select one: a. by the precipitation of minerals from water solution. b. by the cementing together of loose grains of preexisting rock. c. from shell fragments or carbon-rich relicts of plants. d. solidification from a melt.

d. solidification from a melt.

Graphite is: Select one: a. the polymorph of galena. b. harder than glass. c. pure silicon. d. the "lead" in the pencil you write with.

d. the "lead" in the pencil you write with.

Magma may cool and crystallize to become solid igneous rock Select one: a. when its volatile content increases. b. more slowly in the presence of circulating groundwater. c. faster if the surface area of the intrusion is low. d. very slowly (centuries to a million years) when it forms a deep pluton.

d. very slowly (centuries to a million years) when it forms a deep pluton.