Unit 4 · 10–15% of the exam Beta

Unit 4 practice test: Earth Systems and Resources

12 exam-style questions from the unit, free, with an explanation for every option. Most have four answer choices, as on the real exam, and a few ask you to type a calculation with its units; sets share one data table, graph, model or passage.

Covers: Plate Tectonics; Soil Formation and Erosion; Soil Composition and Properties; Earth's Atmosphere; Global Wind Patterns; Watersheds; Solar Radiation and Earth's Seasons; Earth's Geography and Climate; El Niño and La Niña.

Passage

A forecast bulletin

Over the past three months the trade winds across the central Pacific have been well below normal, and surface water from the date line to the coast of South America is now 1.5 °C warmer than average. Forecasters expect these conditions to last through the coming winter. Coastal Peru and Ecuador should prepare for heavy rain and flooding. Parts of Indonesia and eastern Australia face a higher risk of drought and wildfire. In the United States, the southern states are likely to have a wetter than normal winter. Fishing fleets off Peru should expect smaller catches.

Invented passage for practice, in the style of a seasonal climate outlook.

1. What condition is the bulletin describing?

  1. An El Niño
  2. A La Niña
  3. A normal year
  4. A rain shadow
Show the answer

Weak trade winds and warmer-than-average water from the date line to South America, with rain in Peru and drought in Indonesia, are the signs of El Niño.

  • Correct: An El Niño: Right: these are El Niño conditions.
  • A La Niña: La Niña has stronger trade winds and cooler water in the eastern Pacific.
  • A normal year: The bulletin describes winds and temperatures well away from normal.
  • A rain shadow: A rain shadow is caused by mountains, not by Pacific winds.

2. Which evidence in the bulletin most directly supports the forecast of smaller catches off Peru?

  1. "surface water ... is now 1.5 °C warmer than average"
  2. "Parts of Indonesia and eastern Australia face a higher risk of drought"
  3. "the southern states are likely to have a wetter than normal winter"
  4. "Forecasters expect these conditions to last through the coming winter"
Show the answer

Warm water off South America means weak upwelling of cold, nutrient-rich water, so less food for fish.

  • Correct: "surface water ... is now 1.5 °C warmer than average": Right: warm water signals weak upwelling and fewer nutrients.
  • "Parts of Indonesia and eastern Australia face a higher risk of drought": Drought in Indonesia is a separate effect, far from Peru.
  • "the southern states are likely to have a wetter than normal winter": Rain in the United States does not explain the fish catch.
  • "Forecasters expect these conditions to last through the coming winter": How long conditions last does not explain why catches fall.

3. The bulletin advises Peru to prepare for flooding and Indonesia for drought. What assumption links these two warnings?

  1. The rainy zone moves east with the warm water
  2. Rain falls evenly across the Pacific in each ENSO phase
  3. Droughts and floods are caused by the same local storms
  4. Peru and Indonesia lie in the same large watershed
Show the answer

Warm water feeds rising air and heavy rain. When El Niño moves the warm water east, the rain follows it toward Peru and leaves the western Pacific drier.

  • Correct: The rainy zone moves east with the warm water: Right: the rain follows the warm water east.
  • Rain falls evenly across the Pacific in each ENSO phase: The bulletin's two warnings only make sense if rain shifts, not if it stays even.
  • Droughts and floods are caused by the same local storms: The warnings are for places thousands of kilometers apart, not one storm.
  • Peru and Indonesia lie in the same large watershed: They are on opposite sides of the Pacific, not in one watershed.

Data

Average yearly precipitation by latitude band

05001000150020002500Latitude bandPrecipitation (mm per year)0-10° N10-20° N20-30° N40-60° N60-80° N

4. Which latitude band in the graph gets the most precipitation?

  1. 0-10° N
  2. 20-30° N
  3. 40-60° N
  4. 60-80° N
Show the answer

The 0-10° N bar is tallest, at 2,000 mm per year, where air rises near the equator.

  • Correct: 0-10° N: Right: the band near the equator is the wettest.
  • 20-30° N: 20-30° N gets 450 mm, one of the driest bands, where air sinks.
  • 40-60° N: 40-60° N gets 1,000 mm, half as much as near the equator.
  • 60-80° N: 60-80° N gets 350 mm, the least.

5. Which pattern of air motion matches the shape of the graph?

  1. Rising air near 0° and 60°, sinking air near 30°
  2. Sinking air near 0° and 60°, rising air near 30°
  3. Rising air at each of the latitudes
  4. Sinking air near 0°, rising air near the poles
Show the answer

Precipitation is high near the equator, low near 30°, higher again from 40-60° and low near the poles: wet where air rises, dry where it sinks.

  • Correct: Rising air near 0° and 60°, sinking air near 30°: Right: wet bands match rising air and dry bands sinking air.
  • Sinking air near 0° and 60°, rising air near 30°: This is reversed; sinking air brings dry weather.
  • Rising air at each of the latitudes: Then every band would be wet, but 20-30° and 60-80° are dry.
  • Sinking air near 0°, rising air near the poles: The equator band is the wettest, which needs rising air there.

6. A student concludes from the graph that places farther from the equator always get less rain. Is this conclusion supported?

  1. No: the 40-60° N band gets more rain than the 20-30° N band
  2. Yes: each band is drier than the band closer to the equator
  3. Yes: the 60-80° N band is the driest band on the graph
  4. No: the 0-10° N band gets less rain than the 10-20° N band
Show the answer

Rain falls from 2,000 to 450 mm by 20-30° N, then rises to 1,000 mm at 40-60° N before falling again. The pattern is not a steady decline.

  • Correct: No: the 40-60° N band gets more rain than the 20-30° N band: Right: rainfall rises again in the middle latitudes.
  • Yes: each band is drier than the band closer to the equator: The 40-60° N band (1,000 mm) is wetter than the 20-30° N band (450 mm).
  • Yes: the 60-80° N band is the driest band on the graph: The driest band does not show a steady decline; the middle of the graph rises.
  • No: the 0-10° N band gets less rain than the 10-20° N band: 0-10° N gets 2,000 mm, more than 10-20° N (1,100 mm).

7. The Hawaiian Islands form a chain. The island of Hawaii in the southeast has active volcanoes, and the islands get older toward the northwest. What best explains this pattern?

  1. The Pacific Plate moves northwest over a fixed hot spot
  2. A transform boundary runs along the chain of islands
  3. The islands sit on a divergent boundary that spreads both ways
  4. Each island formed when two ocean plates collided there
Show the answer

The hot spot stays in place deep below. The plate slides over it, carrying each finished volcano away, so the oldest islands are farthest from the hot spot.

  • Correct: The Pacific Plate moves northwest over a fixed hot spot: Right: the plate carries older volcanoes northwest, away from the hot spot.
  • A transform boundary runs along the chain of islands: Transform boundaries cause earthquakes; they do not build a line of volcanoes that get older in one direction.
  • The islands sit on a divergent boundary that spreads both ways: A spreading boundary would make rock older in both directions, away from a central ridge.
  • Each island formed when two ocean plates collided there: Hawaii is in the middle of the Pacific Plate, far from any plate boundary.

8. Soil in a tropical rainforest forms faster than soil in the tundra on the same kind of rock. What best explains this?

  1. Warmth and water speed up weathering and decomposition
  2. Rainforest bedrock is softer than tundra bedrock everywhere
  3. Tundra plants add more organic matter, which slows soil formation
  4. Wind erosion is stronger in the rainforest, which adds new soil
Show the answer

Chemical weathering and the work of decomposers both speed up when it is warm and wet. Cold, frozen tundra slows both.

  • Correct: Warmth and water speed up weathering and decomposition: Right: climate controls how fast rock weathers and dead matter decays.
  • Rainforest bedrock is softer than tundra bedrock everywhere: The question says the rock is the same kind, so rock type is not the difference.
  • Tundra plants add more organic matter, which slows soil formation: Tundra plants grow slowly and add little organic matter, and more organic matter would build soil, not slow it.
  • Wind erosion is stronger in the rainforest, which adds new soil: Wind erosion removes soil; rainforests are also sheltered from wind by trees.

9. Why is a soil rich in clay and humus usually more fertile than a sandy soil?

  1. Clay and humus hold nutrients against leaching
  2. Clay and humus let water pass through faster than sand
  3. Sand grains release substances that are toxic to roots
  4. Clay and humus raise the temperature of the soil
Show the answer

Tiny clay particles and humus have huge surface areas that hold nutrients, and humus releases nutrients as it decays. Water washes nutrients through sand quickly.

  • Correct: Clay and humus hold nutrients against leaching: Right: clay and humus hold onto nutrients.
  • Clay and humus let water pass through faster than sand: Clay and humus slow water down; sand drains fastest.
  • Sand grains release substances that are toxic to roots: Sand is not poisonous; it just holds few nutrients.
  • Clay and humus raise the temperature of the soil: Fertility is about nutrients, not soil temperature.

10. Why does the temperature rise with height in the stratosphere?

  1. Ozone there absorbs ultraviolet light
  2. It is closer to the Sun than the troposphere
  3. Warm air from the ground rises and collects there
  4. Clouds in the stratosphere trap heat from below
Show the answer

As ozone absorbs UV light, it warms the air around it. The most absorption is in the upper stratosphere, so temperature climbs with height.

  • Correct: Ozone there absorbs ultraviolet light: Right: ozone absorbing UV heats the stratosphere.
  • It is closer to the Sun than the troposphere: A few kilometers is nothing compared with the 150 million km to the Sun.
  • Warm air from the ground rises and collects there: Air rising from the ground cools as it rises and stops at the top of the troposphere.
  • Clouds in the stratosphere trap heat from below: The stratosphere is too dry for ordinary clouds.

11. What separates one watershed from the next?

  1. A divide: a ridge or high ground
  2. A river: the main channel in the valley
  3. A dam: a wall across the valley
  4. A water table: the top of the groundwater
Show the answer

Water flows downhill, so the high ground between two valleys decides which way rain runs. That ridge line is the divide.

  • Correct: A divide: a ridge or high ground: Right: a divide of high ground separates watersheds.
  • A river: the main channel in the valley: The main river runs through the middle of a watershed, not along its edge.
  • A dam: a wall across the valley: A dam sits across a river inside one watershed.
  • A water table: the top of the groundwater: The water table is underground; watersheds are set by the land surface.

12. In June, Chicago (42° N) has long, warm days while Buenos Aires (35° S) has short, cool days. Why?

  1. The Northern Hemisphere tilts toward the Sun in June
  2. Chicago is closer to the Sun than Buenos Aires in June
  3. The Southern Hemisphere gets very little sunlight in June
  4. Buenos Aires lies farther from the equator than Chicago
Show the answer

In June the North Pole leans toward the Sun, so the Northern Hemisphere has summer while the Southern Hemisphere, tilted away, has winter.

  • Correct: The Northern Hemisphere tilts toward the Sun in June: Right: the hemispheres have opposite seasons because of the tilt.
  • Chicago is closer to the Sun than Buenos Aires in June: Both cities are the same distance from the Sun.
  • The Southern Hemisphere gets very little sunlight in June: The Southern Hemisphere still gets sunlight; it is just less direct and for fewer hours.
  • Buenos Aires lies farther from the equator than Chicago: Buenos Aires (35°) is closer to the equator than Chicago (42°), yet it is in winter.

Keep going

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Practice has every question in the unit, with feedback after each one; the notes for every topic are free. Other units: Unit 1 · Unit 2 · Unit 3 · Unit 4 · Unit 5 · Unit 6 · Unit 7 · Unit 8 · Unit 9.