Q&A Hero

Q: The Hawaiian Islands are near one end of a hot-spot track that stretches to Alaska.

Q: Scientists have been able to accurately forecast earthquakes for approximately a decade.

Q: History seems to teach us that humans are generally unable or unwilling to perceive hazards in a familiar environment.

Q: Radon gas emissions and changes in the magnetic field are some of the phenomena that often occur prior to a quake.

Q: A seismic gap refers to ruptures in the land surface that result from an earthquake.

Q: Paleoseismology estimates expected earthquake activity based on past earthquake activity.

Q: The elastic-rebound theory explains what happens to the Earth's plates during an earthquake.

Q: An earthquake with a high rating on the moment magnitude scale can receive a low rating on the Mercalli scale.

Q: The Richter scale replaced the moment magnitude (M) scale for measuring earthquake magnitude.

Q: Amplitude is the height of a seismic wave and is directly related to the amount of ground movement.

Q: All earthquakes re-rated using the moment magnitude scale have been rated higher than they had been rated using the Richter scale.

Q: Prior to the invention of seismometers, damage to terrain and structures and severity of shaking were used to assess an earthquakes size.

Q: Some aftershocks rival the main shock in magnitude.

Q: The Sierra Nevada and Grand Tetons are examples of tilted-fault block mountain systems.

Q: The Appalachian Mountains are older than the Rocky Mountains.

Q: Oceanic trenches form when one oceanic plate collides with another oceanic plate.

Q: I an oceanic plate-continental plate collision, denser continental crust dives beneath oceanic crust.

Q: Orogens are markably well correlated with the plate tectonics model.

Q: Orogenesis may begin with the capture of migrating terranes.

Q: An orogeny is usually caused by large-scale deformation and uplift of crust.

Q: A playa is a dry lakebed characterized by an area of salt crust left behind by evaporation of water.

Q: The Basin and Range Province of the interior western United States is a type of horst-and-graben topography.

Q: The San Andreas fault is principally the result of compressional stress.

Q: A thrust fault is associated with compressional stress.

Q: In a reverse fault, the hanging wall moves upward relative to the footwall.

Q: A normal fault is associated with compressional stress.

Q: In a normal fault, the hanging wall drops (moves downward) relative to the footwall.

Q: Compressional forces associated with converging plates produce blocks that move upward relative to the footwall block; this is called a thrust or reverse fault.

Q: Oil and gas tend to concentrate in the low areas of a fold; i.e., near the bottom of a syncline.

Q: Folding occurs when rocks are deformed as a result of compressional stress and shortening.

Q: Shortening or folding of the crust is produced by strain caused by tension.

Q: Geologically speaking, the continents began forming relatively recently.

Q: Terranes often differ in rock composition and structure from the continental plate to which they accreted.

Q: Terranes refer to the topography of a tract of land.

Q: A continental shield is a large region where a craton is exposed at the surface.

Q: Cratons are generally of low elevation and old in age.

Q: Whereas mountains occur on every continent, depressions (basins) only occur in Asia and Africa.

Q: Extensive plains are found in North and South America, Asia, and Australia.

Q: The Earth's landscapes are generalized to 12 topographic regions, each defined based on specific, statistical criteria.

Q: The relief from the Earth's highest point to its lowest point is approximately 50 km (31 mi).

Q: The measurement of land elevations relative to sea level is known as hypsometry.

Q: Landscapes are grouped into orders of relief by scale, from continents and ocean basins to individual landforms.

Q: The Alps are examples of the second order of relief.

Q: The first order of relief is the most detailed order and includes mountains, cliffs, valleys, hills, and other landforms.

Q: Modern technologies, such as GPS, LiDAR, and radar are important tools for studying the Earth's topography.

Q: The average elevation of all Earth's surface is slightly above sea level at this time in Earth's history.

Q: The topography of Earth's surface has had relatively little influence on human activities and culture.

Q: Increased seismicity in Colorado, New Mexico, and Oklahoma has been linked toA) a rift valley hot spot in the mid-continental region.B) injection wells associated with hydraulic fracturing.C) a continental plate-continental plate subduction zone.D) a strike-slip fault.

Q: Composite cones have steep slopes and experience ________ eruptions because they are composed of ________ magma. A) mild; mafic B) mild; felsic C) violent; mafic D) violent; felsic

Q: Lava plateaus, such as the Columbia River Plateau, are formed from ________ magma which has a ________ viscosity. A) granitic; high B) granitic; low C) basaltic; high D) basaltic; low

Q: A cinder cone is formed from relatively ________ viscosity magma with a ________ gas content. A) high; high B) high; low C) low; high D) low; low

Q: The eventual catastrophic eruption of Mount Saint Helens was A) a total surprise. B) within only a few days of the first earthquake. C) not preceded by any physical activity. D) related to seafloor subduction at the west coast of North America.

Q: Volcanoes formed from silica-rich magma A) have gently sloping surfaces that give them the appearance of a shield. B) are highly explosive and dangerous. C) are associated with midocean ridges. D) are associated with rift zones.

Q: Volcanic activity located away from plate boundaries is associated with A) subduction and melting of plates along collision zones. B) hot spots. C) rift zones. D) all of the above.

Q: Which of the following statements about shield volcanoes is correct? A) They occur in shield areas of Earth. B) They are subject to violently explosive eruptions. C) They form from mafic magma. D) They consist of tremendous quantities of pyroclastics.

Q: Pulverized rock and clastic materials ejected violently during an eruption are called A) cinders. B) explosive debris. C) tephra, or pyroclastics. D) volcanic ash.

Q: Explosive eruptions tend to build up A) shield-shaped volcanoes. B) plateau basalts. C) composite volcanoes. D) many subsequent lava flows.

Q: An effusive eruption ________, whereas an explosive eruption ________. A) is an outpouring of low-viscosity magma onto the ground; is a violent explosion of magma, gas, and pyroclastics B) produces composite volcanoes; produces shield volcanoes C) is a violent explosion of magma, gas, and pyroclastics; produces shield volcanoes D) produces composite volcanoes; is an outpouring of low-viscosity magma onto the ground

Q: A gently sloping mountain landform built from effusive eruption is known as a A) cinder cones. B) craters. C) calderas. D) shield volcano.

Q: Effusive eruptions are not related to which of the following? A) magma rich in iron and magnesium B) low-viscosity magma C) magma with a 50-75 percent silica content, high in aluminum D) the volcanic activity in Hawaii

Q: Large, basin-shaped depressions that form when summit materials on a volcanic mountain collapse inward after an eruption or loss of magma are known as A) cinder cones. B) craters. C) calderas. D) domes.

Q: Small conical-shaped hills with truncated tops that formed during moderately explosive volcanic eruptions are known as A) cinder cones. B) craters. C) calderas. D) domes.

Q: Circular surface depressions usually found at or near the summit of a volcano are known as A) cinder cones. B) craters. C) calderas. D) domes.

Q: Volcanic activity generally does not occur A) along sea-floor spreading centers. B) in association with plutons. C) in association with hot spots over plumes in the mantle. D) along subduction boundaries.

Q: Molten rock that pours forth on Earth's surface is called A) metamorphic. B) magma. C) intrusive. D) lava.

Q: An active volcano is defined as one that A) has erupted at least once within the past decade. B) has erupted at least once within the past century. C) has erupted at least once within recorded history. D) exhibits activity indicative of an imminent eruption.

Q: Within the United States, which area has the highest earthquake hazards? A) west coast B) east cost C) Gulf coast D) mid-continent.

Q: The slight increase in rock volume produced by small cracks that form under stress and accumulated strain is known as A) dilatancy. B) paleoseismology. C) seismic gaps. D) geodesy.

Q: A seismic gap refers to an area that A) is overdue for an earthquake, based on past earthquake frequency. B) has significant surface fracturing due to fault movement. C) has had tectonic plates separate, leaving large cracks in the surface. D) is lacking seismometers or other measuring devices.

Q: The study of plate boundaries and the frequency of past earthquakes in order to forecast earthquakes is known as A) dilatancy. B) paleoseismology. C) perceptual studies. D) geodesy.

Q: Small surface irregularities along a fault plane that prevent movement and are generally areas of high strain are termed A) asperities. B) focal points. C) elastic spots. D) fore points.

Q: Which of the following is not used to rate an earthquake on the moment magnitude scale? A) the amount of fault slippage that occurred B) the size of the subsurface or surface area that ruptured C) the amount of death and destruction that occurred D) the nature of the ground materials affected by the quake

Q: What is the expected number of an M 5-5.9 or Mercalli V-VII earthquakes per year? A) 1 B) 1319 C) 134 D) 13,000

Q: What is the expected number of an M 8.0 or Mercalli XII earthquakes per year? A) 120 B) 800 C) 1 D) 13,000

Q: The phrase "considerable-to-serious damage to buildings" would be used in the ________ scale. A) Richter B) Modified Mercalli Intensity C) Beaufort D) Moh's

Q: The energy released by a magnitude 8 quake on the Richter scale is how many times greater than that of a magnitude 6 quake? A) 3.15 B) 31.5 C) 63 D) 992 E) 31,255

Q: Which of the following is correct regarding the moment magnitude scalea scale which quantifies the amount of energy released by an earthquake? A) It is a scale of magnitude based on arithmetical progressions (1,2,3,4, etc.). B) It is a closed scale that begins at 0.0 and ends at 10.0. C) It considers the amount of fault slippage produced by the earthquake, the size of the surface (and subsurface) area that ruptured, and the nature of the materials that faulted. D) It is the same as the Mercalli scale.

Q: An instrument used to record vibrations in the crust is the A) land barometer. B) seismometer. C) the Richter scale. D) tiltmeter.

Q: The area at the surface directly above the subsurface location where seismic waves are initiated is termed the A) epicenter. B) fault area. C) Richter zone. D) focus, or hypocenter.

Q: The subsurface area where the motion of seismic waves is initiated along the fault plane is called the A) epicenter. B) fault area. C) Richter zone. D) focus, or hypocenter.