Deck 14: Mass Wasting: the Work of Gravity

Question 1

Which of the following is the dominant lava erupted from volcanoes in Hawaii and Iceland?

A) rhyolite
B) basalt
C) komatiite
D) andesite

Answer 1

B

Question 2

What would you name a light pink, aphanitic, fragmental pyroclastic with sparse quartz phenocrysts?

A) andesite breccia
B) quartz porphyry
C) rhyolite tuff
D) porphyritic granite

Answer 2

C

Question 3

Which of the following are used for studying rocks with a polarizing microscope?

A) polished cubes
B) thin sections
C) broken chips
D) grain karats

Answer 3

B

Question 4

The earliest formed crystals (phenocrysts) in a magma tend to be .

A) crowded and irregular in shape
B) larger and well formed because they have space to grow and a ready supply of ions
C) small and clouded with inclusions of everything that formed later on
D) those that can form only at the lowest temperatures

Question 5

All of the following are factors that affect the generation of magma except for .

A) heat
B) crystal size
C) volatiles
D) pressure

Question 6

What do pumice and obsidian have in common?

A) basaltic composition
B) glassy texture
C) phaneritic texture
D) ultramafic composition

Question 7

Which of the following igneous rocks exhibit phaneritic texture?

A) diorite; gabbro
B) granite; tuff
C) tuff; breccia
D) basalt; pumice

Question 8

Which igneous texture indicates two, distinctly different sizes of mineral grains?

A) aphanitic
B) phaneritic
C) glassy
D) porphyritic

Question 9

What is the rock colour (total % of dark minerals) of a typical granite or rhyolite?

A) 25- 45%
B) > 85%
C) 45- 85%
D) < 25%

Question 10

Vesicles are .

A) holes that used to be full of hot liquid water when the rocks erupted
B) empty pits where large crystals like phenocrysts weathered out during exposure
C) the sex organs of fossilized creatures that once lived in the molten magma
D) cavities or bubble- shaped holes formed in lavas or pyroclastics by escaping gases during quenching

Question 11

Felsic rocks have silica contents of are rich in .

A) around 50%, pyroxene and plagioclase feldspar
B) more than 85%, calcium rich feldspars and amphiboles
C) about 70%, quartz and feldspar
D) under 40%, olivine and pyroxene

Question 12

Felsic rocks like granite .

A) make up most of the ocean floor and volcanic island chains
B) are major constituents of the continental crust
C) are extremely rare on Earth but abundant on the Moon
D) form mainly in volcanic island chains

Question 13

Yellowstone National Park is most famous for what?

A) komatiites; ultramafic lavas
B) diamonds in rhyolite veins
C) rich copper ore deposits
D) rhyolitic volcanism

Question 14

What would you name an intermediate coloured, coarse fragmental volcanic rock with large amphibole and plagioclase phenocrysts?

A) hornblende andesite breccia
B) porphyritic hornblende gabbro
C) hornblende diorite porphyry
D) hornblende granite porphyry

Question 15

Three processes contribute to the formation of every igneous rock: .

A) extrusion, intrusion, and consolidation
B) partial melting, buoyant rise, and crystallization
C) volcanism, plutonism, and magmatic differentiation
D) assimilation, crystallization, and dyke injection

Question 16

What would you call an aphanitic, vesicular, black rock having small pale green phenocrysts of olivine and small white lath shaped phenocrysts of plagioclase?

A) basalt
B) rhyolite
C) obsidian
D) andesite

Question 17

typically exhibit pyroclastic textures.

A) Gabbros
B) Granites
C) Diorites
D) Welded tuffs

Question 18

What name would you assign to a dense phaneritic green rock having olivine and pyroxene as dominant minerals?

A) gabbro
B) granite
C) diorite
D) peridotite

Question 19

Changing the composition of magma by incorporating surrounding host rock is known as

A) assimilation
B) differentiation
C) magma mixing
D) partial melting

Question 20

The mechanism of magmatic differentiation involving the removal of denser, early formed high temperature mineral phases is .

A) assimilation
B) zone refining
C) crystal settling
D) magma mixing

Question 21

Plutonic rocks are emplaced at depth yet they can be seen at the Earth's surface due mainly to

A) erosion of overlying rocks due to uplift
B) widespread igneous inversion
C) continual ongoing intrusion after the magma solidifies
D) catastrophic violent upheavals that bring them to the surface

Question 22

Which magma is most likely to quench (congeal) to a natural glass?

A) highly viscous; cools quickly
B) highly fluid; cools slowly
C) highly viscous; cools slowly
D) highly fluid; cools quickly

Question 23

Exceptionally coarse grained felsic plutonic rocks that are rich in rare minerals and trace elements are probably .

A) welded tuffs
B) porphyrys
C) pegmatites
D) obsidians

Question 24

Tabular sills and lava flows often have regular geometric grids of vertically oriented, thermal shrinkage cracks called .

A) hot flashes
B) arthritic joints
C) honeycomb fractures
D) columnar joints

Question 25

In a porphyritic volcanic rock, which mineral grains are the last to crystallize?

A) vesicles
B) phenocrysts
C) matrix or groundmass
D) pegmatites

Question 26

Which of the following igneous rock always has a pyroclastic texture?

A) intrusive granite pluton
B) rhyolitic tuff
C) porphyritic basalt flow
D) andesitic lava flow

Question 27

Silicate igneous rocks make up the .

A) bulk of volcanic mountains but not much else on Earth
B) majority of shallow rocks covering the continents but everything deeper is sedimentary and metamorphic
C) bulk of the Earth's crust and mantle
D) densest rocks and are mainly found in the core

Question 28

What phenocryst minerals would you expect to find in a porphyritic andesite?

A) Ca- rich plagioclase and olivine
B) muscovite and biotite
C) intermediate (Ca- Na) plagioclase and amphibole or pyroxene
D) Na- rich plagioclase and K- feldspar

Question 29

Which of the following is the dominant feldspar in basalt?

A) pyroxene
B) orthoclase
C) microcline
D) plagioclase

Question 30

Which statement best describes the crystallization of magmas?

A) During crystallization, which can occur over an interval of about 200° C, the composition of the residual melt continuously changes as particular ions are selectively removed and incorporated into certain minerals that crystallize early at high temperature.
B) A felsic magma produces only one rock type equal to the melt composition by crystallizing quartz, feldspar, and ferromagnesian minerals in fixed proportions and compositions until all of the melt is used up.
C) Like the freezing of water, cooling magmas hit their crystallization temperature and stop cooling until all the melt has crystallized, whereupon cooling resumes.
D) Early formed crystals are big and irregular in shape, but gradually get smaller and have better developed faces with time as they react with the residual melt.

Question 31

Which of the following minerals crystallize early in Bowen's reaction series?

A) quartz
B) biotite
C) muscovite
D) olivine

Question 32

The rare pyroxene spodumene is mined from granite pegmatites for its high content of the element

A) Li
B) Pt
C) Cs
D) Kr

Question 33

Name the texture that requires a magnifying glass or microscope to see individual mineral grains.

A) phaneritic
B) aphanitic
C) pegmatitic
D) porphyritic

Question 34

A _ is a near surface, intrusive, igneous rock body that results from local inflation of a horizontal sill.

A) volcanic neck
B) laccolith
C) batholith
D) dike

Question 35

Which of the following best describes an aphanitic texture?

A) The rock consists of broken, volcanic- rock and mineral fragments.
B) The rock is crystalline; mineral grains are of distinctly different sizes.
C) The rock is crystalline; mineral grains are too small to be visible without a magnifying lens or microscope.
D) The mineral grains have glassy textures.

Question 36

What is/are thought to be the main mechanism(s) for generating basaltic melts from hot peridotite near its melting point in the upper mantle?

A) drop of confining pressure or introduction of water
B) frictional heating of basaltic ocean crust as it slides down subduction zones
C) intrusion of hotter solid mantle rocks from below
D) conductive heating of basaltic ocean crust subducted into the mantle

Question 37

While the ultramafic rock, peridotite, comprises the bulk of the mantle, the earth hasn't been hot enough to make much (its volcanic equivalent) since the Precambrian.

A) andesite
B) welded tuff
C) gabbro
D) komatiite

Question 38

In what texture are mineral grains of roughly equal size and coarse enough to be seen without a microscope or magnifying glass?

A) phaneritic
B) porphyritic
C) pegmatitic
D) aphanitic

Question 39

Intermediate rocks like andesite and diorite .

A) are major constituents of the oceanic crust
B) form mainly in volcanic island arcs and convergent continental margins
C) rarely contain plagioclase feldspar, pyroxenes or amphiboles
D) contain the semiprecious gems beryl, topaz, and tourmaline

Question 40

How long does it take for a large magma body at great depth to cool and completely crystallize?

A) a few days
B) several tens to a hundreds of thousands of years
C) a few months
D) several years

Question 41

Mafic rocks like basalt and gabbro .

A) make up most of the ocean floor and volcanic island chains
B) are very low in their iron and magnesium contents
C) form mainly in continental mountain belts
D) are major constituents of the continental crust

Question 42

Visible quartz and potassium feldspar grains are the main constituents in which igneous rock?

A) rhyolite
B) gabbro
C) granite
D) basalt

Question 43

Which of the following igneous rocks is thought to be common in the Earth's mantle but rare in the crust?

A) pumice
B) peridotite
C) granite
D) pegmatite

Question 44

What weight percentage of silica (SiO2) typifies granites and rhyolites?

A) 90%
B) 50%
C) 30%
D) 70%

Question 45

Magmas rise to shallower depths and intrude the crust or extrude on the surface because .

A) of centrifugal and tidal forces as the Earth spins
B) the pressure at depth is so great that the magmas are forced upwards
C) of buoyancy, the magmas are hotter and less dense than the surrounding rocks where they form
D) earthquakes shake the crust and allow the magma to escape upwards

Question 46

The behaviour and processes that govern the textures of magmatic rocks depend on the content of a magma's three distinct parts: .

A) quartz, feldspar, and ferromagnesian minerals
B) andesite, basalt, and rhyolite
C) high pressure, medium pressure, and low pressure
D) solid, liquid, and gas

Question 47

The aphanitic equivalent of granite is

A) komatiite
B) rhyolite
C) andesite
D) basalt

Question 48

Explosive volcanic eruptions occur .

A) when crystallization forces exceed the strength of the volcano
B) when violently escaping gases evolve suddenly to drop the magma density and propel molten magma from the chamber
C) in response to deflation of the volcano
D) whenever basaltic magma extrudes on the seafloor

Question 49

What is the rock colour (total % of dark minerals) of a typical gabbro or basalt?

A) 25- 45%
B) < 25%
C) > 85%
D) 45- 85%

Question 50

The mechanism of selectively removing the minerals which melt at the lowest temperature is

A) magma mixing
B) assimilation
C) magmatic differentiation
D) partial melting

Question 51

What is the most common extrusive rock type for any volcanic environment on the Earth or even on the Moon?

A) rhyolite
B) obsidian
C) andesite
D) basalt

Question 52

Which of the following high silica igneous rocks can be of low enough density to float on water?

A) obsidian
B) granite
C) rhyolite
D) pumice

Question 53

Light coloured aphanitic rocks .

A) consist predominantly of large ferromagnesian minerals
B) never form at the surface of the Earth
C) consist predominantly of small non- ferromagnesian minerals
D) always form deep in the crust

Question 54

What are vesicles?

A) open voids in an igneous rock left when phenocrysts dissolved away
B) the fragments comprising a volcanic breccia
C) the larger mineral grains of a porphyritic texture
D) open spaces formed in the rock as the lava solidified around gas bubbles

Question 55

The most common non- ferromagnesian silicate minerals (>40 %) in most igneous rocks are

A) olivine
B) feldspar
C) quartz
D) calcite

Question 56

Which phaneritic, igneous rock is comprised mainly of olivine, pyroxene, and calcium rich plagioclase?

A) gabbro
B) basalt
C) rhyolite tuff
D) granite

Question 57

What two rock types are often found interlayered in the same volcanic deposit?

A) obsidian and pumice
B) andesite and komatiite
C) granite and gabbro
D) peridotite and basalt

Question 58

Which texture would be most unlikely to occur in an extrusive igneous rock?

A) glassy
B) pyroclastic
C) aphanitic
D) phaneritic

Question 59

The process of is driven by and transforms a magma into an igneous rock.

A) volcanism, internal heating
B) partial melting, pressure increase
C) intrusion, overlying rock weight
D) crystallization, cooling (heat loss)

Question 60

A(n) texture would be most unlikely to occur in an extrusive igneous rock.

A) pyroclastic
B) aphanitic
C) glassy
D) phaneritic

Question 61

Mafic rocks have silica contents of and are mainly composed of .

A) around 50%, pyroxene and plagioclase feldspar
B) up to 70% quartz and feldspar
C) under 40%, olivine and pyroxene
D) more than 85%, potassium rich feldspars and micas

Question 62

Which of the following has the same mineral composition as andesite?

A) granite
B) gabbro
C) basalt
D) diorite

Question 63

A is the largest, discordant body of intrusive, igneous rock.

A) batholith
B) pluton
C) laccolith
D) lopolith

Question 64

The last minerals to crystallize in Bowen's reaction series result in igneous rocks with a composition.

A) mafic
B) felsic
C) ultramafic
D) intermediate

Question 65

When a rock has a two- stage cooling history (slow then fast) or has minerals that crystallized at different temperatures and grew at different rates it is .

A) porphyritic
B) aphanitic
C) phaneritic
D) pyroclastic

Question 66

is composed mainly of ferromagnesian minerals.

A) Andesite
B) Peridotite
C) Granite
D) Rhyolite

Question 67

What would you name an intermediate coloured (35% dark minerals), phaneritic rock with large greenish- black amphibole phenocrysts?

A) porphyritic hornblende gabbro
B) hornblende diorite porphyry
C) porphyritic hornblende granite
D) hornblende andesite breccia

Question 68

Which of the following igneous rocks usually exhibit aphanitic texture?

A) rhyolite, gabbro
B) andesite, rhyolite
C) granite, gabbro
D) andesite, diorite

Question 69

Rocks that consist completely of disordered ions with no long range structures are called .

A) phaneritic
B) aphanitic
C) glassy
D) porphyritic

Question 70

Which of the following igneous rocks is composed mainly of ferromagnesian minerals with less than 20% feldspar?

A) granite
B) rhyolite
C) andesite
D) peridotite

Question 71

The size, shape, and geometric arrangement of mineral grains in igneous rocks is called and it indicates .

A) geomorphology, depth of origin for the original magma
B) texture, the environmental conditions in which the rock formed
C) aphanitic form, how much water was present in the melt
D) igneous geometry, the original % of partial melting

Question 72

The main factors which directly govern the development of texture in all igneous rocks are

A) cooling rate, dissolved volatiles, and silica content
B) weathering and climate
C) buoyancy, crystal settling, and partial melting
D) volcano or pluton size and shape

Question 73

The aphanitic equivalent of diorite is

A) basalt
B) andesite
C) rhyolite
D) komatiite

Question 74

The molten portion of magmas and lavas is made up of .

A) silicate minerals that have already crystallized
B) solid high pressure forms of water, carbon dioxide, and sulfur dioxide
C) complex anion frameworks of oxygen with silicon and aluminum and cation modifiers made up of different amounts of calcium, sodium, iron, magnesium, and potassium
D) metamorphic fluids

Question 75

Which igneous rock or magma has the lowest silica (SiO2) content?

A) andesite
B) basalt
C) peridotite
D) granite

Question 76

As the silica content varies from less than 40% to more than 70% there is a systematic .

A) decrease in the quartz content of the rocks
B) decrease in calcium, magnesium, and iron with an increase in sodium and potassium
C) increase in calcium, magnesium, and iron with a decrease in sodium and potassium
D) increase in the temperature at which point melting begins

Question 77

As melts cool their viscosity increases (they lose their mobility and get stiffer) even before they start to crystallize because .

A) their ions become more disordered
B) the silica tetrahedra in the melt start to link up and make larger and stronger units
C) they increase in volume
D) all of the sodium and potassium escape

Question 78

A _ is an intrusive, igneous rock body that is tabular and concordant.

A) dike
B) pluton
C) sill
D) laccolith

Question 79

The most common ferromagnesian silicate minerals by % in igneous rocks are .

A) aragonite, barite, calcite, and diamond
B) olivine, pyroxene, amphibole, and biotite
C) magnetite, chromite, hematite, and ilmenite
D) feldspar, quartz, and muscovite

Question 80

What igneous rock is named for a prominent, volcanic mountain range in western South America?

A) peridotite
B) andesite
C) basalt
D) pegmatite