Geology Test 2 (online quizzes) – Flashcards
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In which mountain range does Mount St. Helens occur?
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Cascade mountain range
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Which of the following does not affect a magma's viscosity?
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Volume of magma
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What typically triggers a Hawaiian-type eruption?
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The arrival of a new batch of melt into a near-surface magma reservoir causes the magma chamber to swell and fracture the rock above.
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What is a plume of hot ash and gases that extends thousands of meters into the atmosphere during an explosive volcanic eruption?
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An eruption column
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What composition is 90% of the lava erupted on Earth?
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Basaltic
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What type of lava flow means "on which one can walk" and resembles twisted braids of ropes?
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Pahoehoe flows
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What feature forms when a lava flow forms underwater along the mid-oceanic ridge?
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Pillow lava
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What is the most abundant gas expelled during a volcanic eruption?
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Water vapor
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What is a fumarole?
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A small vent that emits only gases from a volcano
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How many total shield volcanoes are found on the Big Island of Hawaii?
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Five
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What material comprises cinder cone volcanoes, which have a high angle of repose?
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Loose pyroclastic material
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Which of the following volcanic hazards can occur when a volcano is not erupting?
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Lahar
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What destroyed the city of Pompeii and when?
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in 79 ad; eruption of Mount Vesuvius
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What is the smallest of the three volcano types?
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Cinder Cone
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Which type of caldera forms from the collapse of a volcano caused by subterranean drainage from a central magma chamber?
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Hawaiian-type caldera
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What type of lava occurs in lava domes that form when lavas squeeze out of a vent, producing a dome-shaped mass?
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Felsic
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What type of plate boundary produces continental volcanic arcs?
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Ocean-to-continent convergent plate boundaries
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What type of volcanism supposedly produced both Hawaii and Yellowstone?
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Intraplate (hot spot)
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Which volcanic hazard poses the greatest threat to human life?
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Pyroclastic flows
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How many people live in the vicinity of an active volcano?
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500 million
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What is the difference between magma and lava?
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Magma is molten rock inside Earth, and lava is molten rock at Earth's surface.
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What is the "melt" of a magma composed of?
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Mobile silicon, oxygen, aluminum, potassium, calcium, sodium, iron, and magnesium ions
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Do extrusive igneous rocks tend to be fine-grained or coarse-grained?
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Fine-grained, because they form when molten rock cools quickly at the surface
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Which of the following is richer in silica?
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Nonferromagnesian (light) silicates
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What type of igneous rock is peridotite?
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Ultramafic
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Viscosity refers to a fluid's resistance to flow. The more viscous the magma, the "thicker" it is. How does silica content affect a magma's viscosity?
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The greater the silica content, the more viscous the magma.
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What does a phaneritic texture indicate?
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A slow rate of cooling
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What is the name of large crystals in an igneous rock with a porphyritic texture?
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Phenocrysts
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Which igneous rock has a glassy texture?
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Obsidian
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What two basic characteristics are used to classify igneous rocks?
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Texture and mineral composition
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What mineral gives some granites a pinkish color?
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Potassium feldspar
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What igneous rock floats on water and resembles a gray, frothy mass of intertwined glass shards?
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Pumice
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What is diorite?
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A phaneritic igneous rock with the same composition as andesite
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What effect does the addition of volatiles such as water have on a descending slab of oceanic lithosphere at a subduction zone?
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Lowers the melting temperature
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What is the average geothermal gradient in the upper crust?
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25 degrees Celsius per kilometer depth
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What does Bowen's reaction series illustrate?
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Minerals crystallize from a cooling magma in a systematic fashion.
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What name refers to the formation of one or more secondary magmas from a single parent magma?
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Magmatic differentiation
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What igneous intrusion is forcibly injected between sedimentary strata, causing the beds above to arch?
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Laccolith
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Of the descriptions given, which rock type and environment has the highest concentration of rare elements?
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Pegmatite; crystallized from a water-rich, highly differentiated residual magma
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Which of the following statements about diamonds is true?
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Diamonds are transported from the mantle to the surface via kimberlite pipes.
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Which type of sedimentary rock forms when ions in a solution are precipitated through inorganic or biological processes?
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chemical sedimentary rock
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Which of the following is a collective term for all of the chemical, physical, and biological changes that take place after sediments are deposited and during and after lithification?
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diagenesis
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What are the primary constituents of detrital sedimentary rocks?
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quartz and clay minerals
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What is the primary basis for classifying detrital sedimentary rocks?
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particle size
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Which of the following detrital sedimentary rocks is likely to be well sorted?
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quartz sandstone from ancient dunes
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Which of the following sedimentary rocks is associated with deposition in an oxygen-poor swamp environment?
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black shale
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Which of the following chemical sedimentary rocks is soft, porous, and made almost entirely of the hard parts of microscopic calcareous marine organisms?
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chalk
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When a body of seawater evaporates, the minerals precipitate in sequence of their solubility. What is the correct sequence of mineral precipitation from least soluble (first) to most soluble (last)?
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gypsum, halite, sylvite
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Which is the highest-grade coal with the greatest concentration of carbon?
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anthracite
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What two processes occur during lithification of unconsolidated sediment into solid rock?
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compaction and cementation
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How might an iron oxide cement be identified on a sedimentary rock?
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Rock will have an orange, dark red, or rust-colored appearance.
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What type of texture do all detrital sedimentary rocks have?
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Clastic
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Which sedimentary environment category would most glacial deposits belong to?
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continental
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Which of the following sedimentary structures can be used to determine the direction of ancient wind or water currents?
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ripple marks
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Graphite is a nonmetallic mineral resource. What was formerly a common use for graphite?
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pencil lead
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Which of the following is not a resource derived from sedimentary rocks?
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marble building stones
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Coal is formed mostly from a(n) ____ environment, whereas oil and natural gas form from a(n) ____ environment.
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swamp; oxygen-poor marine
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What percentage of the energy consumed in the United States today comes from fossil fuels?
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82 percent
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Which of the following is a way in which carbon is removed from the atmosphere?
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plant photosynthesis
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What type of sedimentary rock is dolostone?
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Chemical sedimentary rock
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Which of the following happens to a rock during metamorphism?
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It remains essentially solid.
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To what does the term parent rock of a metamorphic rock refer?
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the preexisting sedimentary, igneous, or metamorphic rock that underwent metamorphism
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What is the ultimate goal of a rock as it gradually changes in response to a new set of environmental conditions?
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to reach equilibrium with the new environment
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Which of the following is not an agent of metamorphism?
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magnetism
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At what depth and temperature do clay minerals tend to become unstable and begin to recrystallize?
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8 km; 200° C
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What is differential stress?
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stress placed on a rock by unequal forces, which squeeze a rock greater in one direction than in others
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Which of the following is a foliated metamorphic rock?
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schist
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In what direction, relative to the direction of differential stress, do foliations typically form?
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perpendicular
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What is the accessory mineral in a staurolite mica-schist?
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staurolite
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How can a student tell slate and phyllite apart?
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Phyllite has a glossy sheen and a somewhat wavy surface, whereas slate is fine-grained and breaks into flat slabs.
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Which type of metamorphism occurs when a meteorite strikes the Earth surface at high speed?
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impact metamorphism
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Where does most hydrothermal metamorphism occur?
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mid-ocean ridge systems
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What is burial metamorphism?
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metamorphism that occurs when massive amounts of sedimentary or igneous material accumulates in a subsiding basin
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Can metamorphic rocks contain fossils?
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Yes, when a sedimentary parent rock undergoes low-grade metamorphism, some of the fossils can persist.
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What happens to grain size as metamorphic intensity increases?
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It increases.
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Which index mineral indicates extremely high-grade metamorphism?
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sillimanite
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What are migmatites?
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rocks transitional between igneous and metamorphic
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What is the parent rock for gneiss?
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granite or shale
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What rock forms along fault zones and is composed of broken and crushed rock fragments?
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fault breccia
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Which of the following types of metamorphism is related to differential stress?
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regional metamorphism
