Q&A Hero

Q: Most granitic batholiths represent ________. A) a deeply exhumed passive continental margin B) a deeply exhumed forearc rock assemblage C) magmas generated in a rift system, prior to development of a passive margin D) the exhumed roots of a subduction related magmatic arc

Q: Island arcs and Andean type mountains are both examples of mountains formed by ________. A) collisional tectonics B) subduction C) rifting/oceanic spreading D) transform faults

Q: The figure above is an oblique Google earth image from southwestern North America looking approximately north. The view is approximately 50km across. The area is a classic area of normal faulting. What is the modern theory for orogenesis? A) geosynclinal theory B) shrinking earth model C) expanding earth theory D) plate tectonics theory

Q: The figure above is an oblique Google earth image from southwestern North America looking approximately north. The view is approximately 50km across. The area is a classic area of normal faulting. The area labeled C shows an active fault bounding the range. Which best describes the motion on the fault? A) west side up B) east side up C) north side down D) south side down E) right lateral strike-slip

Q: The figure above is an oblique Google earth image from southwestern North America looking approximately north. The view is approximately 50km across. The area is a classic area of normal faulting. This area represents what type of mountain system A) Fault block mountains B) Andrean type mountains C) Collisional orogen D) Strike-slip mountains

Q: Southwestern North America contains a large area called the Basin and Range province. What is the origin of this name? A) Ranges are uplifted horst blocks adjacent to basins formed as graben. B) The area is characterized by chains of volcanos forming ranges next to basins that form valleys. C) Thrust faulting along the San Andreas fault produces linear ridges, the ranges, with intervening basinal valleys forming fault block mountains. D) Folds have formed by compressional stresses along the plate margin forming ridges (ranges) and valleys (the basins) of the basin and range province.

Q: Mountain building uplifts rocks against the force of gravity raising their potential energy, which requires work by the earth system. Based on the relative motion of fault blocks, what type of fault would you expect to require more energy than the others? A) normal B) strike-slip C) thrust D) There is no way of knowing.

Q: Grabens are formed by what type of faulting? A) normal B) reverse C) strike-slip D) collision

Q: In thrust faulting, ________. A) grabens develop on the footwall block B) the crust is shortened and thickened C) horizontal, tensional stresses drive the deformation D) the hanging wall block slips downward along the thrust fault

Q: In a(n) ________ fault, the hanging wall block moves up with respect to the footwall block. A) normal B) strike slip C) reverse D) abnormal

Q: A(n) ________ fault has little or no vertical movements of the two blocks. A) stick slip B) oblique slip C) strike slip D) dip slip

Q: Most active faults pose a risk to society because they can potentially produce ________. A) landslides B) tsunamis C) earthquakes D) disruptions in groundwater flow

Q: A transform fault is ________. A) a strike-slip fault that forms the boundary between tectonic plates B) a dip-slip fault connecting an anticline with a syncline C) a reverse fault that steepens into a thrust fault D) the rift bounding fault on a mid-ocean ridge

Q: The San Andreas Fault in California and the Alpine Fault in New Zealand are examples of ________. A) normal faults B) thrust faults C) strike-slip faults D) oblique-slip normal faults

Q: You are walking north across dipping beds in sedimentary rocks. You walk across 200m of rocks with a relatively constant dip of 20 degrees to the south. Suddenly you come to beds with lower dip that become flat lying, and then dip north across a horizontal distance of only about 30m. As you walk on the beds become more steeply dipping until they dip almost 80 degrees to the north. You walk across these steeply dipping beds for 40m, and then beds return to a south dip of about 20 degrees. What kind of structure(s) did you just walk across? (A sketch may help you solve this problem.) A) a symmetric anticline B) an asymmetric syncline C) an asymmetric anticline and syncline D) an asymmetric anticline E) a symmetric syncline

Q: In a monocline, one of the limbs of the fold ________. A) is horizontal B) is vertical C) dips in the same direction as the other limb, but at a lower angle D) has a shallower dip in the opposite direction of the other limb

Q: In an overturned fold, the beds have rotated ________. A) more than 180 degrees B) more than 90 degrees C) more than 45 degrees D) 100 to 150 degrees

Q: Large circular downwarped structures are called ________. A) anticlines B) synclines C) basins D) domes

Q: Monoclines, anticlines, synclines and domes are all examples of ________. A) faulting B) jointing C) flow D) foliation

Q: Burial of rocks increases the confining pressure so that deeply buried rocks are more likely to ________ than shallow rocks. A) fracture B) fold C) deform D) shear

Q: The higher the temperature, the more likely it is that a rock will deform ________. A) ductilely B) brittlely C) elastically D) shearingly

Q: Folds are an example of ________. A) brittle deformation B) ductile deformation C) elastic deformation D) shear deformation

Q: Use the figure below to answer the following questions. In the figure, which of the deformations appears most similar to what might be expected along a divergent plate boundary? A) original B) X C) Y D) Z

Q: Use the figure below to answer the following questions. In the figure, which of the deformations appears most similar to what might be expected along a transform plate boundary? A) original B) X C) Y D) Z

Q: Use the figure below to answer the following questions. In the figure, the stress on block 'Z' is ________. A) shear B) folding C) tensional D) compressional

Q: Use the figure below to answer the following questions. In the figure, the stress on block 'Y' is ________. A) shear B) folding C) tensional D) compressional

Q: Use the figure below to answer the following questions. In the figure, the stress on block 'X' is ________. A) shear B) folding C) tensional D) compressional

Q: Use the figure below to answer the following questions. The concepts of "stress" and "strain" are related because ________. A) "strain" causes "stress" B) "stress" causes "strain" C) compressional "stress" causes a convergent plate boundary to form D) compressional "strain" causes a convergent plate boundary to form

Q: Use the figure below to answer the following questions. The material in the figure was ________ when the folding occurred. A) ductile B) elastic C) brittle D) strong

Q: When subjected to a differential stress, a very "brittle" material, like glass, will ________. A) not bend at all. It will only break. B) deform by breaking or elastic bending C) flow or shear if the stress is large enough D) flow under low to moderate stress conditions

Q: The slopes of most cinder cones are usually about 30 degrees because ________. A) the loose materials ejected from the cone form slopes at the angle of repose B) cinder cones are mostly basalt and basalt is too weak to maintain a slope greater than 30 degrees C) they are composites of loose material and lava and the viscosity of the lava requires the slopes to form at about 30 degrees D) The statement is false; most cinder cones have slopes less than 10 degrees because of the low viscosity of basalt lava flows.

Q: Paricutin is an example of a ________. A) shield volcano B) cinder cone C) lava dome D) composite volcano

Q: Cinder cones ________. A) have very steep slopes B) are usually less than 300 meters (1000 feet) high C) consist largely of pyroclastics D) all of these

Q: A geologist is working in an area of old volcanic rocks exposed by erosion. He finds a large rock outcrop that contains flat lying gravels in the base of the outcrop. These gravels are overlain by basalt that forms a series of layers representing flows. The uppermost basalt lava flows have a dip of about 10 degrees to the west. What does this outcrop record? A) Basalt flows formed above a series of gravels, filling a river valley. B) Basalt flows formed after gravels were deposited, covered the local terrain, and built a shield volcano with dips of about 10 degrees. C) Gravels were initially deposited in a river valley and a cinder cone was erupted, damming the valley, before a cinder cone formed. D) You can't tell anything about the history of this region from this outcrop.

Q: Where are the most active volcanoes in the world? A) Washington State, in the United States B) Mexico C) Italy D) Hawaii

Q: Shield volcanos form from what type of magma? A) high viscosity aa basalt magmas B) low viscosity rhyolite magmas C) low viscosity basalt magmas D) high viscosity rhyolite magmas

Q: Kilauea is an example of a ________. A) shield volcano B) cinder cone C) lava dome D) volcanic neck

Q: The average composition of rocks comprising a large composite cone or stratovolcano is similar to a(n) ________ magma. A) basaltic B) ultramafic C) andesitic D) rhyolitic

Q: Which of the following volcano types are short lived volcanos that last a few days to months and then shut down? A) shield volcano B) cinder cone C) lava dome D) composite volcano

Q: Which one of the following statements concerning cinder cones is false? A) They are small volcanoes with fairly steep sides. B) They are built mostly or entirely during one eruptive cycle. C) The cinders and other pyroclastic particles are consolidated into welded tuff. D) The cinders most commonly are basaltic.

Q: A volcanic deposit comprised of red to black lapilli-sized pyroclastic material associated with pahoehoe lava flows was probably deposited on ________. A) a large composite volcano B) a shield volcano C) a cinder cone D) a satellite shield volcano on a rhyolitic caldera

Q: Pillow lavas are ________. A) basaltic magmas erupted on the seafloor as magma blobs from an explosive, submarine eruption B) basaltic lava tubes erupted on the seafloor in volcanic piles analogous to toothpaste extruded from a tube C) andesitic bombs erupted from a cinder cone that accumulate as pillow-like masses around the cone D) rhyolite glasses that develop a banding that resembles a pillow case with internal snowflake obsidian that looks like feathers

Q: A rock outcrop exposes a layer of obsidian overlain by volcanic ash and a layer with fragments of lapilli. What rock composition and eruptive type fits this description? A) basalt erupted from a cinder cone B) basalt flows and interbedded andesite deposited on a shield volcano C) andesite and basalt erupted from a stratovolcano D) rhyolite erupted in violent pyroclastic eruptions

Q: The rock pumice often floats yet the density of the rock is greater than water. Why does it float? A) Pumice is a pyroclastic rock derived from rhyolite glass, and rhyolite glass has a lower density than water. B) Pumice is a pyroclastic rock comprised largely of open voids formed by gases released when the magma solidified as froth-like material. C) Pumice is a rock made of rhyolite glass that erupts into water, which traps water in voids and makes the material less dense than water. D) Pumice is another name for dacite, a low-density rock that floats in water.

Q: Which of the following is not considered pyroclastic debris? A) ash B) cinders C) bombs D) pahoehoe

Q: Which one of the following statements concerning volcanic blocks and bombs is true? A) Blocks are broken fragments of solid rocks; bombs have smaller sizes than lapilli. B) Bombs are guided to Earth by laser beams; blocks fall anywhere. C) Bombs are ejected as magma lumps; blocks are ejected as solid fragments. D) Bombs and blocks are both smaller than lapilli and cinders.

Q: Which type of basaltic lava flow has its surface covered with sharp-edged, angular blocks and rubble? A) scoria B) pahoehoe C) pillow lava D) aa

Q: ________ are usually the most abundant gases emitted during basaltic volcanism. A) Chlorine and sodium B) Neon and ammonia C) Oxygen and nitrogen D) Water and carbon dioxide

Q: ________ magma is the most abundant type of magma erupted on Earth. A) Basaltic B) Granitic C) Andesitic D) Pegmatitic

Q: Volcanic bombs originate ________. A) as laser-guided, granite blocks launched from a supersonic jet B) as blocks of volcanic rock ejected from an erupting volcanic crater C) as erupted magma blobs that partly congeal before falling to the ground D) as ash particles that join together in the eruptive plume and fall as cobble-sized objects

Q: Which type of basaltic lava flow has a fairly smooth, unfragmented, ropy surface? A) aa B) pegmatitic C) pahoehoe D) scoria

Q: In the movie "Volcano" basaltic lava flows are shown running down flat streets at speeds faster than humans could run. From your knowledge of magma viscosity, is this realistic? A) Yes, the viscosity of basalt magma is similar to water so it would flow at comparable rates. B) No, the viscosity of basaltic magma is much higher than water, and thus, would flow much slower than water. C) No, the viscosity of basaltic magma is much higher than water, and thus, would flow much faster than water. D) There is no way of knowing because basaltic magmas can have viscosities similar to water or higher depending on temperature and fluids, and thus there isn't enough information.

Q: Volcano A erupts rocks with SiO2 content ranging from 49% to 52% whereas volcano B, 100km away, erupts materials with SiO2 content of 62-68%. Which statement best characterizes these two volcanos? A) Both volcanos are shield type volcanos that are characterized by quiescent eruptions. B) Both volcanos are violent, explosive volcanos that spread ash continent wide. C) Volcano A is likely to be a supervolcano with violent eruptions, whereas volcano B is probably a shield volcano with quiescent eruptions. D) Volcano A is probably a shield volcano with typically quiescent eruptions, whereas Volcano B is likely a stratovolcano characterized by violent, explosive eruptions.

Q: Why does magma viscosity vary with silica content? A) Increasing silica increases a tendency for silica bonds to link up in networks, acting like a polymerization of the magma. B) Increasing silica content lowers the melting temperature and since increasing the temperature of a magma decreases viscosity increasing silica content increases viscosity. C) Increasing silica content increases the amount of water a magma can dissolve and water decreases magma viscosity, so increasing silica content decreases magma viscosity. D) There is no correlation between silica content and magma viscosity.

Q: As magma approaches the surface, water contributes to the explosive potential of the eruption because ________. A) water has a large heat capacity, which allow it to keep the magma hot enough to explode B) water dissociates to hydrogen and oxygen at high temperatures but reacts violently at decreasing pressures to produce explosive eruptions C) water has a lower density in its solid phase than its liquid phase which makes it explode when pressure decreases D) water dissolved in magma flashes to steam as pressure decreases, and the volume increase leads to an explosive potential

Q: What type of volcanic material is indicative of eruption under water? A) AA flows B) Pyroclastic flows C) Pillow lavas D) Pahoehoe flows E) Lava aprons

Q: Which one of the following shows the correct order (left to right) of decreasing magma viscosity? A) rhyolite, andesite, basalt B) andesite, rhyolite, basalt C) basalt, rhyolite, andesite D) basalt, andesite, rhyolite

Q: Which magma type would generally have the lowest viscosity? A) basalt B) andesite C) dacite D) rhyolite

Q: ________ tend to increase the explosive potential of a magma body beneath a volcano. A) High viscosity and dissolved gas B) High viscosity and low dissolved gas content C) Low silica content and low viscosity D) Low viscosity and low dissolved gas content

Q: Which of the following factors help determine whether a volcanic eruption will be violent or relatively quiescent? A) amount of dissolved gas in the magma B) temperature of the magma C) composition of the magma D) all of these

Q: ________ is the major dissolved volatile constituent in both magmas and volcanic gases. A) Water B) Carbon monoxide C) Hydrogen chloride D) Methane

Q: Considering the history of Mt. St. Helens and Kilauea volcanoes and your knowledge of volcano types in different tectonic settings, if you had to live on a volcano, which of the following would you choose if safety was your only concern? A) Mt. Spurr in the Aleutian volcanic arc B) Mt Fujiyama in the Japanese island arc C) Mt. Rainier in the Cascades just north of Mt. St. Helens D) Mauna Loa in Hawaii, on the Big Island of Hawaii near Kilauea

Q: Which statement about the May, 1980, eruption of Mount St. Helens is false? A) During the eruptive period, the mountain peak was substantially built up by new lava flows and pyroclastic debris. B) Plumes of ash rose high into the atmosphere during the major eruptive events. C) Mudflows accompanied the major eruptive events. D) The most powerful explosive event was preceded by a massive landslide.

Q: In 1980, ________ was the first Cascade Range volcano to erupt since Mt. Lassen in 1915-16. A) Mt. Rainier B) Mt. Shasta C) Kilauea D) Mt. St. Helens

Q: Briefly summarize at least 4 major volcanic hazards. Describe the level of risk from most dangerous to least dangerous to human life. For each hazard indicate where the hazard is located relative to the volcano (on the volcano slopes, anywhere within several km of the volcano, anywhere within thousands of km of the volcano, in river valleys near the volcano, near bodies of water near the volcano, etc.) and consider if the probability of the hazard is very low, low, medium, high, or high, within the danger zone of the hazard.

Q: Volcanoes are generally not preserved in the geologic rock record because the upper part of the volcano is eroded away. However, the igneous rocks associated with volcanoes are often found preserved in the rock record as layers of volcanic rock and associated intrusions. How could you infer what type of volcano erupted in a given area based on the type of volcanic deposits? Give specific examples and briefly discuss if some materials may be linked to different types of volcanoes.

Q: Match the name of the tectonic feature with the Figure. oceanic spreading center

Q: Match the name of the tectonic feature with the Figure. continental rift

Q: Match the name of the tectonic feature with the Figure. convergent plate margin

Q: Match the name of the tectonic feature with the Figure. Hot spot

Q: Bomb

Q: Vent

Q: Pyroclastic material

Q: Lava flow

Q: Magma chamber

Q: The dominant rock type erupted by submarine volcanoes at spreading ridges is andesite.

Q: The main mechanism for melting at spreading ridges is decompression melting of ultramafic mantle rock.

Q: Many magmas are generated when solid rocks are carried to higher levels in the earth by flow and partially melted by decompression melting.

Q: Magmas are the product of melting in the deep part of the earth that forms a layer of molten material called the asthenosphere.

Q: Volcanos have no significant impact on weather and climate.