Q&A Hero

Q: According to the geothermal gradient, there is an increase in temperature with increasing depth. If that is the case, why isn't the entire interior of the planet molten?

Q: Is the force of gravity the same over the Earth's surface? Explain why or why not.

Q: What is chemical convection, and how does it affect the outer core?

Q: The inner core has not always existed, but formed over time. Explain how conditions in the Earth changed over time to create an inner core.

Q: Scientists have subdivided the upper mantle into three sections based on environmental and compositional differences. What are these three subdivisions and how do they compare to each other?

Q: Explain how a P-wave shadow will form. Between which degrees will it form?

Q: Explain why S waves are unable to pass through the outer core.

Q: Match the heat transfer mechanisms to the correct description of how heat is transported in or from the Earth. A) Heat is transported away from Earth and into outer space. B) Heat flows between two materials in contact with each other. C) Warm, low-density materials rise and cool, high-density materials sink. 1. Convection 2. Conduction 3. Radiation

Q: Match the layer of Earth to the compositional materials. A) Ferromagnesian silicates mostly in a ductile state B) Liquid nickel and iron with trace materials C) Basaltic material composing the outermost layer D) Granitic material composing the outermost layer E) Solid nickel and iron with trace materials 1. Asthenosphere 2. Inner core 3. Continental crust 4. Outer core 5. Oceanic crust

Q: Put the layers of Earth in order from the surface (First Layer) to the center (Fourth Layer). A) Outer core B) Upper mantle C) Crust D) Lower mantle E) Inner core 1. First Layer (Surface) 2. Second Layer 3. Third Layer 4. Fourth Layer 5. Fifth Layer (Center of Earth)

Q: Seismic tomography requires only the data from one earthquake in order to "see" all parts of the Earth's interior.

Q: The inner core is shrinking.

Q: The mantle is composed of pure nickel and iron.

Q: In the D" layer, the portion of the mantle closest to the core-mantle Boundary is hypothesized to be partially melted because the S-wave velocities decrease by 30% when passing through it.

Q: Oceanic crust is compositionally more similar to the mantle than to continental crust.

Q: P waves cannot penetrate the outer core because it is liquid.

Q: The inner core and the outer core are compositionally the same. The major difference between them is the states of matter in which they exist.

Q: The magnetic north pole is currently moving (toward /away from) the geographic North Pole, and the magnetic south pole is currently moving (toward /away from) the geographic South Pole. A) toward; toward B) toward; away from C) away from; toward D) away from; away from

Q: If the outer core is cooler than the inner core, why is it in a liquid state? A) It has more radioactivity than in the inner core. B) It is under less pressure than the inner core. C) It has greater water content than the inner core. D) It has higher density materials than the inner core.

Q: Which of the following factors contributed toward the early increase in temperature in the Earth's interior? A) Impact from planetesimals B) Friction between landmasses C) Friction between landmasses and radioactive decay D) Radioactive decay and impact from planetesimals

Q: Which process is responsible for Earth's magnetic field? In which layer does this process occur? A) Radiation; upper mantle B) Subduction; lower mantle C) Convection; outer core D) Crystallization; inner core

Q: Since humans cannot access the core, what objects do scientists use as a proxy to determine the composition of the inner and outer core? A) Volcanic rocks B) Meteorites C) Comets D) Glaciers

Q: Outside of the crust, the layer that scientists know the most about is the mantle. Other than via seismic waves, how else do geologists obtain information about the composition of the mantle? A) Drill cores B) Volcanoes C) Sonar D) Seismic waves

Q: What physical property of continents makes them difficult to subduct? A) Age B) Temperature C) Low density D) Thickness

Q: The following choices contain densities of various materials. Based on this data, which will yield the fastest seismic velocity? A) 2.7 g/cm3 B) 3.0 g/cm3 C) 3.3 g/cm3 D) 5.6 g/cm3

Q: When olivine is undergoing a mineral phase change due to pressure, what mineral will it form? A) Perovskite B) Quartz C) Pyroxene D) Spinel

Q: What is the average density of oceanic crust? A) 2.7 g/cm3 B) 3.0 g/cm3 C) 3.3 g/cm3 D) 5.6 g/cm3

Q: What is the average density of continental crust? A) 2.7 g/cm3 B) 3.0 g/cm3 C) 3.3 g/cm3 D) 5.6 g/cm3

Q: Why is conduction not an efficient way to move heat through most of the Earth? A) Radioactive decay generates too much heat. B) Molecules are too far apart to transfer heat via that method. C) Rocks are poor conductors of heat. D) Radiation is the most efficient way to move heat through the interior.

Q: ________ are responsible for the heat generated in the interior today. A) Meteorite impacts B) Magma plutons C) Short-lived radioactive isotopes D) Nuclear reactions

Q: What is the dominant mineral in the lower mantle? A) Perovskite B) Olivine C) Quartz D) Pyroxene

Q: Why might there be density changes between different parts of the same layer of the planet? A) Different materials make up different regions of the same layer. B) Some materials may compress when squeezed by overlying rock. C) Repelling forces may cause some atoms to expand. D) Differentiation is still separating materials into distinct interior layers.

Q: A ________ occurs when an iron-rich fluid in the core is electrically charged and flowing, which generates a magnetic field. A) geotherm B) geodynamo C) geophysical anomaly D) geosyncline

Q: Which of the following material properties will not result in a seismic velocity anomaly when using seismic tomography? A) Confining pressure B) Composition C) Temperature D) Water content

Q: Which of the following materials would cause the greatest gravity anomaly? A) Quartz B) Water C) Granite D) Metallic ore

Q: How is the shape of Earth affected by its rotation? A) Earth is perfectly round. B) The poles are further from the center of Earth than the equator. C) The equator is further from the center of Earth than the poles.

Q: ________ is a technique to view three-dimensional changes in composition and density by using seismology. A) Magnetometry B) Paleomagnetism C) Chemical convection D) Seismic tomography

Q: Heat will transfer by ________ in the outer core. A) radiation B) convection C) conduction and convection D) conduction

Q: What is the average rate of temperature increase in the mantle? A) 0.3C/km B) 0.7C/km C) 1C/km D) 1.3C/km

Q: What is the average geothermal gradient in the crust? A) 20C/km B) 30C/km C) 45C/km D) 100C/km

Q: Where is the highest rate of heat flow escaping the Earth's interior? A) At mid-ocean ridges B) At subduction zones C) At volcanoes D) At mountain ranges

Q: Of the three mechanisms of heat transfer, which is the only one that does not operate in the interior of Earth? A) Convection B) Radiation C) Conduction

Q: What materials make up Earth's core? A) Perovskite and silica B) Iron and nickel C) Olivine and pyroxene D) Sulfur and aluminum

Q: The inner core is believed to rotate independently from the outer layers of Earth. Why is this possible? A) The immense interior pressures generate rotation. B) The inner core is separated from the mantle by the liquid outer core and can spin freely. C) Radioactive decay generates spin. D) Frictional drag pushes the inner core at a different rate than the rest of the planet.

Q: Which layer is thought to be the birthplace of deep mantle plumes? A) Transition zone B) Outer core C) D" layer D) Shadow zone

Q: The composition of the upper mantle is defined by ________. A) granite B) quartz C) perovskite D) peridotite

Q: How does water get from the surface to the middle of the mantle? A) Percolation via pores and fractures B) Subterranean streams C) Seawater seeping into the interior at mid-ocean rifts D) Subducting oceanic lithosphere

Q: Which layer or layers of the interior are believed to have convection cells? A) Mantle B) Mantle and outer core C) Inner core D) Outer core and inner core

Q: Which layer of Earth makes up more than 82 percent of the volume of the planet? A) Outer core B) Crust C) Mantle D) Inner core

Q: The ________ is a seismic boundary between the crust and the mantle where there is a dramatic increase in seismic wave velocity. A) Schrodinger discontinuity B) Greenschist facies C) Low-velocity pathway D) Moho boundary

Q: Where is oceanic crust generated? A) Along divergent plate boundaries B) Where volcanic lava meets the sea C) Where continents collide D) Where magma bodies are emplaced deep in the crust

Q: Where is the thickest continental crust in North America? A) Appalachian Mountains B) Rocky Mountains C) Basin and Range region D) Great Basin

Q: Where is the thinnest continental crust in North America? A) Appalachian Mountains B) Mississippi River Valley C) Basin and Range region D) Colorado Plateau

Q: What is the average thickness of the oceanic crust? A) 4 km B) 7 km C) 40 km D) 70 km

Q: P waves moving through the base of continents move at about ________ km/sec, but once they cross the Moho, the velocity changes to ________ km/sec. A) 8; 4 B) 2; 10 C) 6; 8 D) 3; 9

Q: Why do seismic waves follow strongly curved paths as they move through the interior? A) Their paths are altered by changes in temperature. B) Their paths are altered by reflection off dense materials. C) Their velocities are altered by changes in chemistry. D) Their velocities are changed because of increasing pressure with depth.

Q: What is diffraction? A) A seismic wave is bounced back toward its source. B) A seismic wave is bent when moving from one material to another. C) A seismic wave is bent when it passes by a curved surface. D) Seismic waves are separated by liquids

Q: Which of the following materials will allow for the fastest transmission of seismic waves? A) Rigid, less compressible material B) Material that has been slightly heated C) Partially molten material D) Molten material

Q: Which seismic wave(s) would be most useful in determining the extent and thickness of the Earth's interior layers? A) P waves B) P and S waves C) S waves D) Surface waves

Q: What will happen to a seismic wave when it is refracted? A) The wave will be bent when passing into a material of differing density. B) The wave will undulate. C) The wave will be bounced back toward its source. D) Nothing will change the wave.

Q: What will happen to a seismic wave when it is reflected? A) The wave will be bent. B) The wave will undulate. C) The wave will be bounced back toward its source. D) Nothing will change the wave.

Q: An earthquake occurs in California. What is the minimum magnitude an earthquake can have if it is to be picked up by seismographic networks around the world? A) M 5.5 B) M 7 C) M 8 D) M 9.5

Q: As of 2015, what was the deepest drill core yet taken that allowed scientists to study the Earth's interior? A) 7.6 km B) 12.3 km C) 15 km D) 50.5 km

Q: What is the primary method scientists use to determine the layering of the interior of the Earth? A) Drill cores B) Volcanic rocks C) Sonar D) Seismic waves

Q: ________ is the process where materials separate into different layers due to density. A) Shearing B) Differentiation C) Phase change D) Tensional stress

Q: Which atom is easier to compress when pressure is squeezing a rock and why? A) Negative ion; it has more electrons and is "fluffier." B) Positive ion; it has fewer electrons and is already densely compact. C) Negative ion; electrons are easier to remove. D) Positive ion; it is less resistant and easier to compress.

Q: What is a mineral phase change? A) A mineral melts from a solid state to a liquid state. B) The exterior of a mineral weathers and changes color. C) A mineral changes density because of the addition of water. D) Atoms in a mineral are rearranged into a denser and more stable structure.

Q: What is the difference in densities between the upper mantle and the lower mantle? A) 2.7 & 3.0 g/cm3 B) 3.0 & 3.3 g/cm3 C) 3.3 &5.6 g/cm3 D) 10 & 12.1 g/cm3

Q: Which one of the following is not one of the three compositionally distinct layers of the Earth's interior? A) Crust B) Mantle C) Lower mantle D) Core

Q: Which physical property is responsible for determining how Earth materials separate into interior layers? A) Density B) Color C) Molecular charge D) Tensile strength

Q: Using the arrival times in this image, determine the S-minus-P interval for this earthquake. A) 6.0 minutes B) 4.1 minutes C) 10.1 minutes D) 3.7 minutes

Q: Note the three arrows on this image, marked A, B, and C, which illustrate three seismic waves on the chart above. Match the name of the seismic wave with the letter indicating that wave. (Note: Surface waves are not differentiated on this diagram and can be described simply with "surface waves.") A) P waves B) S waves 1. A 2. B 3. C

Q: What feature is marked with the circle in this image? A) P wave B) Focus (hypocenter) C) Hanging wall D) Crust

Q: Which seismic waves will cause the greatest damage to buildings?

Q: How might climate change predictions of sea level in the next century affect the severity of future tsunamis?

Q: An urban legend that states that all it would take is one good, strong earthquake for California to fall off into the sea. Is this true? Explain why this may or may not be the case.

Q: The year 2010 was a big one for major earthquakes: Haiti (M 7.0), Chile (M 8.8), Turkey (M 6.1), and New Zealand (M 7.1). With so many major earthquakes in a short time, many people began to wonder about the status of the planet. One major author (name withheld for privacy) even got on TV and stated that these earthquakes were related and were triggering each other. Was this author correct? Why or why not?

Q: On January 12, 2010, the country of Haiti was rocked by a violent M 7.0 earthquake. This quake caused widespread devastation and resulted in the death of over 300,000 people. A month later, an M 8.8 earthquake rocked central Chile, where over 80 percent of the country's population was concentrated. However, only 525 people were reported dead for this disaster. Why would Chile's earthquake, with a higher magnitude, have a lower death toll than Haiti's earthquake?

Q: The New Madrid earthquakes of the early nineteenth century were some of the largest in American history. At their greatest, they caused buildings and bluffs to collapse, caused land subsidence, and displaced parts of the Mississippi River. Could another earthquake of this magnitude happen near New Madrid again? Explain how the earthquake devastation today would compare to that of the early nineteenth century.

Q: Explain why using intensity alone as a measurement of seismic power can pose problems for truly understanding the energy released by the earthquake.