Answers

ConceptChecks

ConceptCheck 5-1: The total amount of water in Earth’s water cycle does not change significantly over short periods of time and water soaking through rocks is part of Earth’s water cycle because it eventually makes its way back into the atmosphere.

ConceptCheck 5-2: In the water cycle, the total amount of water does not change; rather, water changes forms among solid, liquid, and gas. Because the amount of water would be the same, the cup would have the same weight after freezing as it did before.

ConceptCheck 5-3: In our solar system, Earth is the only planet on which these processes appear to have taken place. Plants using photosynthesis convert carbon dioxide into oxygen, and certain bacteria release nitrogen in the atmosphere.

ConceptCheck 5-4: As sunlight warms Earth’s surface, energy in the form of heat increases the temperature of the troposphere near Earth’s surface such that the troposphere is heated from below.

ConceptCheck 5-5: Ozone in the stratosphere absorbs ultraviolet radiation from the Sun and helps warm the stratosphere. So, a deficit of ozone would make the stratosphere cooler in temperature.

ConceptCheck 5-6: By moderating heat loss into outer space, the greenhouse effect keeps Earth’s temperature warmer than it would otherwise be, allowing liquid water and hence life to exist on Earth.

ConceptCheck 5-7: Earth must have significant amounts of iron in its core because Earth’s overall density is much higher than the rocks found at its surface, so the new planet must have far less iron if it were to have a lower average density.

ConceptCheck 5-8: Because longitudinal S waves are unable to travel through liquid, the sudden appearance of S waves suggests that the planet’s interior would have solidified.

ConceptCheck 5-9: The melting temperature would be higher because regions of high pressure increase the temperature at which rocks melt.

ConceptCheck 5-10: When two oceanic plates move apart, molten material wells up in the gap between them. This piles up and produces an underwater mountain chain like the Mid-Atlantic Ridge.

ConceptCheck 5-11: Where oceanic crust material is subducted beneath continental crust, it is plunged into the high-temperature mantle and melts. Occasionally, this material rises in the form of magma-feeding volcanoes.

ConceptCheck 5-12: A supercontinent traps energy in the form of heat beneath it, causing the material directly beneath it to expand and crack. This process allows fissures to be filled by rapidly upwelling material from underneath, breaking the continent apart.

ConceptCheck 5-13: No. Earth’s magnetic field is predominantly created by a dynamo effect caused by the movement of iron-rich material in the liquid core.

ConceptCheck 5-14: The vast majority of charged particles from the Sun’s solar wind are deflected away, while a small portion leaks inside the magnetosphere.

ConceptCheck 5-15: What is glowing are atoms in the outer fringes of Earth’s atmosphere. When struck by fast-moving charged particles that originated on the Sun, electrons in these atoms are excited and then emit light when they return to their normal state.

ConceptCheck 5-16: A 3°C change in ocean surface temperature is sufficient to starve plankton, the base of the food chain, by preventing cooler, nutrientrich water from moving to the surface.

ConceptCheck 5-17: Living plants remove CO2 from the atmosphere through photosynthesis, and burning plants release the CO2 they have captured back into the atmosphere.

ConceptCheck 5-18: Atmospheric ozone prevents much of the Sun’s harmful ultraviolet light from entering Earth’s atmosphere. The ozone hole is a region allowing more of this particular energy to enter Earth’s atmosphere.

ConceptCheck 5-19: The greenhouse effect is the process by which CO2 and other gases maintain Earth’s temperature at a moderate level by preventing heat loss into outer space. By comparison, global warming is the uncontrolled, rapid increase in Earth’s temperature caused by a dramatic increase in atmospheric CO2 concentration due to human activity, making the effect unusually intense.

ConceptCheck 5-20: No. There is no debate—nearly everyone agrees global warming is occurring. The scientific debate is about how much will occur, why it is occurring, how it might be mitigated, and what will be the extent of damage to the biosphere.

CalculationChecks

CalculationCheck 5-1: Using the relationship that distance equals rate times time (6 × 108 cm) ÷ 2 cm/year = 3 × 108 years or 300 million years.

CalculationCheck 5-2: 5 × 109 years ÷ 5 × 108 years/cycle = 10 cycles.

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