The Earth is closer to the Sun in summer and farther away in winter

1. What causes most places on the Earth to have seasons? (Ch. 6, Section “What Causes the Earth’s Seasons?”) 06.01 • The Earth is closer to the Sun in summer and farther away in winter • The spin axis is tilted 23.5° to the plane of the Earth’s orbit, causing solar radiation to vary in angle as the Earth revolves around the Sun • The spin axis changes in tilt causing winter when the tilt is great and summer when the tilt is small • Days are longer during summer than winter, so the extra sunshine causes it to be warmer in summer and less sunshine causes it to be colder in winter • There is more ice in winter, so it is colder, and less in summer, when it is warmer Correct answer: B. Answers A and C are common misconceptions. Answer D sounds right, but it is the tilt that causes seasons, not the varying length of daylight. Answer E is nonsense.

2. If you travel by airplane from New York to Paris (approximately east to west across the Atlantic Ocean), which way do you have to steer the airplane to arrive in at the Paris airport? (Ch. 6, Section “How Does the Coriolis Effect Influence Moving Objects?”) 06.02 • Slightly north of a direct line between airports • Slightly south of a direct line between airports • Along the straight line between airports, because there is no effect on east-west motion • Straight north, allowing the Earth’s rotation to carry the airplane eastward • Straight south, allowing the Earth’s rotation to carry the airplane eastward Correct answer: A. The Coriolis effect bends the path of a moving object to the right in the northern hemisphere, so the plane must be steered to the left (north) to make up for the effect.

3. Why is ocean climate (and the entire Earth for that matter) divided into latitude parallel zones that become progressively colder from equator to pole? (Ch. 6, Section “The Ocean’s Climate Pattern”) 06.03 • Winds are stronger at higher latitudes, so cooling is greater at higher latitudes • Precipitation and cloud cover increase with latitude, causing higher latitudes to be cooler • Greater amounts of ice occur at higher latitudes, making it cooler at higher latitudes • Cold ocean deep water returns to the surface at high latitudes, causing cooling • The average solar radiation (sunlight) striking the surface declines from equator to poles Correct answer: E. The other answers are incorrect.

4. Suppose we could take the Atlantic Ocean north of the equator and divide it into two compartments along a north-south line (for example, if sea level were much lower and the Mid-Atlantic Ridge was emergent along its length). What would happen to the North Atlantic Gyre? (Ch. 7, Section “Main Components of Ocean Surface Circulation: Subtropical Gyres”) 07.02 • The gyre would grind to a halt since its north and south currents are blocked • The Mid-Atlantic Ridge barrier would turn equatorial currents north and northern boundary currents south, resulting in two gyres, one on each side • The ridge would cause surface water to sink as it piles up against the barrier and has nowhere else to go • The ridge would have almost no effect and the currents would just go over or around it • The ridge would cause deep water upwelling as the currents strike the barrier Correct answer: B. Trade winds and westerlies should still drive the currents, the Coriolis effect would still cause currents to bend to the right, and the ridge would cause the northern boundary current of the west gyre to turn south and the southern boundary current of the east gyre to turn north.

5. The Ekman spiral affects the direction of near surface water movement. If you lowered a current measuring device over the side of a ship in the northern hemisphere, what would you observe? (Ch. 7, Section “Ekman Spiral and Ekman Transport”) 07.03 • Subsurface water would all be moving to the right of the wind direction • Subsurface water would all be moving to the left of the wind direction • Subsurface water would be sinking • As the instrument descended, the current direction would move progressively to the left of the wind, until it actually was going in the opposite direction, and at greater depth it would move to the right • As the instrument descended, the current direction would move progressively to the right of the wind, until it actually was going in the opposite direction, and at greater depth it would move to the left Correct answer: E. The other answers are incorrect.

6. What is the main cause of surface water sinking to cause the deep, thermohaline ocean currents? (Ch. 7, Section “Origin of Thermohaline Circulation”) 07.04 • Density increase caused by greater salinity • Density increase caused by cold in polar regions • Density decrease caused by greater salinity • Density decrease caused by cold in polar regions • Surface currents converging, driving them both downward Correct answer: B. Increasing density is the key, and this is mostly caused by cold polar temperatures. Certainly salinity plays a role in increased density (Answer A), but it is usually secondary and often results from evaporation, which means warmer, less dense water. Answers C and D are incorrect because increasing salinity or decreasing temperature do not cause density decrease and less dense water would not sink. Answer E is partly correct – there are places where water sinks owing to convergence, but this is not a major source of thermohaline currents.

7. In the Atlantic, North Atlantic Deep Water (NADW) sinks near Greenland and heads south along the ocean bottom. Antarctic Bottom Water (ABW) sinks off Antarctica and moves north along the ocean bottom. What happens when they meet? (Ch. 7, Section “Sources of Deep Water”) 07.05 • NADW stays on the bottom and ABW overrides it • ABW stays on the bottom and NADW overrides it • ABW and NADW mix to form ocean common water (OCW) • The two water masses collide, causing them to turn upward and rise to the surface • Because of the Coriolis Effect, one goes left and the other goes right, so they never meet Correct answer: B. ABW is usually denser so it stays on the bottom and NADW forms a layer atop it. Answer A has the order wrong. Answer C is correct in other oceans, but not the Atlantic. Answer D is an incorrect statement. Answer E is incorrect because the Coriolis effect pushes both to the west side of the basin.`

8. What happens to a rubber duckie sitting on the water surface when waves pass by? (Ch. 8, Section “Circular Orbital Motion”) 08.01 • It moves in a nearly circular motion, always returning to the same spot • The wave fronts move it progressively forward as they pass • The wave troughs move it progressively backward as they pass • It moves up and down, but not forward or backward • It moves side-to-side, but not up and down Correct answer: A.

9. If you were a submarine commander and wanted to go deep enough that your ship would not feel the effect of 300-foot (91-m) wavelength storm waves, how deep would you have to dive? (Ch. 8 Section “Circular Orbital Motion”) 08.02 • Just beneath the surface • 300 feet • 150 feet • 600 feet • You would feel the waves all the way to the bottom, no matter how deep Correct answer: C. The wave base is L/2, which is 150 feet.

10. Why do tsunami waves always behave as shallow water waves? (Ch. 8, Section “Shallow-Water Waves”) 08.03 • The statement is incorrect; tsunami waves are never shallow water waves • Because they are caused by the gravitational attraction of the Sun and Moon • Because waves generated by tsunami do not have the same behavior as normal wind-generated waves • Their wavelengths are long enough that anywhere in the ocean the water depth is less than L/20 • Tsunami waves are extremely fast, which means they feel the ocean bottom no matter where they are Correct answer: D.

11. What are the primary factors that determine wave height? (Ch. 8, Section “Factors Affecting Wave Energy”) 08.04 • Wind speed and fetch • Wind speed, length of time wind blows in one direction, and fetch • Time that the wind blows from one direction • Water surface tension and wind • Wind speed and the time that the wind blows in one direction Correct answer: B.

12. Which of the following mechanisms is NOT a cause for tsunamis? (Ch. 8, Section “How Are Tsunami Created?”) 08.05 • Earthquakes • Lunar tides • Submarine landslides • Large meteor impacts • Volcanic eruptions Correct answer: B. All of the others can create a tsunami.

13. The lunar tidal bulge has a period of 12 hr 25 min, but the solar tidal bulge period is 12 hr. Why the difference? (Ch. 9 Section “Earth’s Rotation and Tides”) 09.02 • The Moon is closer than the Sun • The Moon has phases • The Moon moves around the Earth in its orbit • The Sun is bigger than the Moon • The Moon’s orbit is at a bigger angle from the rotation axis Correct answer: C.

14. If you are in a boat in an estuary, when will tidal currents going out to sea be strongest? (Ch. 9, Section “Coastal Tidal Currents”) 09.03 • When the full Moon rises • At high tide • At low tide • Halfway between high tide and low tide • Halfway between low tide and high tide Correct answer: D. Maximum tidal currents are halfway between high and low tide. For currents going out of the bay, the proper timing is between high and low tide. When the full Moon rises, on an ideal planet, the tide would be rising and filling the estuary, so the tide would not be going out. On the non-ideal Earth, there is no fixed relation between the Moon’s position in the sky and the tidal phase.

15. Why are spring tides highest when the Moon is near perigee? (Ch. 9, Section “Effects of Elliptical Orbits”) 09.04 • The Moon is moving fastest in its orbit at that time • The Moon is farther from Earth, so gravitational force is greater • The difference between solar and lunar tides is maximum at this time • The Moon and Sun are lined up • The Moon is closer to the Earth, so gravitational force is greater Correct answer: E. Answers A, C, and D are correct but not the answer. Answer B is an incorrect statement.

16. If a point on the coast experiences a semi-diurnal tide, what does the daily tide record show? (Ch. 9, Section “What Types of Tidal Patterns Exist?”) 09.05 • One high tide and one low tide per day • One high tide (half a tide) one day and one low tide the next • Either one or two high tides each day, as long as they don’t change much • Two nearly equal high tides and two nearly equal low tides each day • Two unequal high tides and two unequal low tides each day Correct answer: D. Answer A is a diurnal tide. Answer B does not happen because the Earth’s rotation period is one day. Answer C is incorrect because it mixes diurnal and semi-diurnal tides. Answer E is the definition of a mixed tide.