ESTUDYR
ESS 101 MIDTERM SPECIAL READINGS AND BONUS 2026 MULTICHOICE
ANSWERED EXAM QUESTIONS WITH DETAILED RATIONALES
1. Most of what scientists know about Earth’s early planetary history comes from:
A. Written historical records
B. Fossilized remains of early life
C. The sparse geologic record dating back ~3.5 billion years
D. Modern satellite imagery
✅Correct Answer: C
Rationale:
Earth’s earliest history is reconstructed primarily from ancient rocks, since written and
biological records did not yet exist.
2. Plasma is best described as:
A. A liquid found deep in Earth’s mantle
B. The fourth state of matter that only exists at very high temperatures
C. The most common state of matter in the universe
D. Both B and C
✅Correct Answer: D
Rationale:
Plasma is an ionized gas, making it the fourth state of matter and the most abundant form of
matter in the universe (e.g., stars).
3. Which of the following statements is NOT true?
A. Photosynthesis is the primary source of atmospheric oxygen
B. Oxygen must be continuously replenished to remain in the atmosphere
C. If photosynthesis stopped, atmospheric oxygen would disappear in less than 1 million
years
D. Oxygen reacts readily with many Earth materials
✅Correct Answer: C
, ESTUDYR
Rationale:
While oxygen would decline without photosynthesis, it would not disappear that rapidly; the
statement exaggerates the timescale.
4. The ~20,000-year climate cycle in East Africa, alternating between extreme aridity and
wet conditions, is driven primarily by:
A. Sunspot cycles
B. Plate tectonic movement
C. Changes in Earth’s orbital precession (Milankovitch cycles)
D. Volcanic eruptions
✅Correct Answer: C
Rationale:
Orbital variations alter solar radiation patterns, driving long-term climate cycles.
5. The first major dispersal of early human ancestors out of East Africa into Eurasia may
have been caused by:
A. Global glaciation
B. Increased volcanic activity
C. Coastal migration only
D. Ephemeral deep freshwater lakes forming and disappearing along the East African Rift
Valley
✅Correct Answer: D
Rationale:
Temporary lakes created habitable corridors, facilitating migration.
6. Interest in alternative energy and mineral resources may involve which of the following?
A. Producing unconventional resources
B. Mining lower-grade ore deposits
C. Recovering materials through recycling and waste streams
D. Sourcing resources from countries with different political or environmental standards
E. All of the above
✅Correct Answer: E
ESS 101 MIDTERM SPECIAL READINGS AND BONUS 2026 MULTICHOICE
ANSWERED EXAM QUESTIONS WITH DETAILED RATIONALES
1. Most of what scientists know about Earth’s early planetary history comes from:
A. Written historical records
B. Fossilized remains of early life
C. The sparse geologic record dating back ~3.5 billion years
D. Modern satellite imagery
✅Correct Answer: C
Rationale:
Earth’s earliest history is reconstructed primarily from ancient rocks, since written and
biological records did not yet exist.
2. Plasma is best described as:
A. A liquid found deep in Earth’s mantle
B. The fourth state of matter that only exists at very high temperatures
C. The most common state of matter in the universe
D. Both B and C
✅Correct Answer: D
Rationale:
Plasma is an ionized gas, making it the fourth state of matter and the most abundant form of
matter in the universe (e.g., stars).
3. Which of the following statements is NOT true?
A. Photosynthesis is the primary source of atmospheric oxygen
B. Oxygen must be continuously replenished to remain in the atmosphere
C. If photosynthesis stopped, atmospheric oxygen would disappear in less than 1 million
years
D. Oxygen reacts readily with many Earth materials
✅Correct Answer: C
, ESTUDYR
Rationale:
While oxygen would decline without photosynthesis, it would not disappear that rapidly; the
statement exaggerates the timescale.
4. The ~20,000-year climate cycle in East Africa, alternating between extreme aridity and
wet conditions, is driven primarily by:
A. Sunspot cycles
B. Plate tectonic movement
C. Changes in Earth’s orbital precession (Milankovitch cycles)
D. Volcanic eruptions
✅Correct Answer: C
Rationale:
Orbital variations alter solar radiation patterns, driving long-term climate cycles.
5. The first major dispersal of early human ancestors out of East Africa into Eurasia may
have been caused by:
A. Global glaciation
B. Increased volcanic activity
C. Coastal migration only
D. Ephemeral deep freshwater lakes forming and disappearing along the East African Rift
Valley
✅Correct Answer: D
Rationale:
Temporary lakes created habitable corridors, facilitating migration.
6. Interest in alternative energy and mineral resources may involve which of the following?
A. Producing unconventional resources
B. Mining lower-grade ore deposits
C. Recovering materials through recycling and waste streams
D. Sourcing resources from countries with different political or environmental standards
E. All of the above
✅Correct Answer: E
