Unit 4: Earth Systems and Resources

Original practice questions written to the published framework for this section. No expert has reviewed them, and they are not taken from any official exam. Try each one before you open the answer.

1. Question 1Foundational

   What type of plate boundary is found where two plates move apart and new crust forms, as at the Mid-Atlantic Ridge?

   1. AA convergent boundary
   2. BA transform boundary
   3. CA subduction zone
   4. DA divergent boundary

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   Answer: D. A divergent boundary

   At a divergent boundary magma rises into the gap between separating plates and solidifies, creating new seafloor and a mid-ocean ridge. A subduction zone is the tempting distractor, but that is one kind of convergent boundary where crust is destroyed rather than created. Transform boundaries involve plates sliding past one another with little crust made or lost.

   Key insight: Divergent boundaries build crust, convergent boundaries consume it, and transform boundaries just grind.

2. Question 2Foundational

   In which layer of the atmosphere does essentially all weather occur?

   1. AThe troposphere
   2. BThe stratosphere
   3. CThe mesosphere
   4. DThe thermosphere

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   Answer: A. The troposphere

   The troposphere is the lowest layer, holds most of the atmosphere's mass and nearly all of its water vapor, and cools with altitude, so warm air rises and drives convection and storms. The stratosphere is the tempting distractor because it contains the ozone layer, but its temperature increases with altitude, which makes it stable and largely free of vertical mixing. That stability is also why jet aircraft cruise near its base.

   Key insight: Temperature falling with altitude allows convection, which is why weather lives in the troposphere.

3. Question 3Intermediate

   Which soil texture has the largest particles, the highest permeability, and the lowest water-holding capacity?

   1. AClay
   2. BSilt
   3. CSand
   4. DLoam

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   Answer: C. Sand

   Sand particles are the largest of the three texture classes, so the pores between them are wide and well connected and water drains through quickly. Clay is the opposite extreme: its tiny particles pack tightly, hold water against gravity, and drain very slowly. Loam is a balanced mixture of sand, silt, and clay, which is why it is generally the most productive agricultural soil.

   Key insight: Bigger particles mean bigger pores, faster drainage, and less water held for plants.

4. Question 4Intermediate

   Why are most of the world's large deserts located near 30 degrees north and 30 degrees south latitude?

   1. AThe Coriolis effect prevents clouds from forming at those latitudes
   2. BDry air descending at the edge of the Hadley cells suppresses precipitation there
   3. CThose latitudes receive the most direct solar radiation all year
   4. DOcean currents are always warmest at those latitudes

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   Answer: B. Dry air descending at the edge of the Hadley cells suppresses precipitation there

   Air heated at the equator rises, cools, and drops its moisture as tropical rain, then travels poleward and sinks around 30 degrees. Sinking air warms and its relative humidity falls, so clouds and rain are suppressed and deserts form. The claim about the most direct sunlight is the tempting distractor, but that describes the equator, which is one of the wettest regions on Earth.

   Key insight: Rising air makes rain and sinking air makes deserts, which is why global wind cells set the pattern of biomes.

5. Question 5Advanced

   During an El Nino event, what happens to the Pacific trade winds and to coastal upwelling off western South America?

   1. AThe trade winds strengthen and upwelling increases
   2. BThe trade winds weaken and upwelling increases
   3. CThe trade winds strengthen and upwelling stops entirely
   4. DThe trade winds weaken and upwelling decreases

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   Answer: D. The trade winds weaken and upwelling decreases

   In normal years easterly trade winds push warm surface water toward the western Pacific, which lets cold, nutrient-rich water rise along the South American coast. During El Nino those winds weaken, warm surface water spreads back east, and the thick warm layer blocks upwelling, so nutrient supply and fishery productivity fall. The tempting distractor pairs the correct wind change with the wrong upwelling response.

   Key insight: Weak trade winds mean warm surface water piles against South America, and warm surface water shuts down upwelling.