Edgenuity Earth and Space Science Answers – Top MCQs (Updated)
1. What is the primary source of energy for Earth’s climate system?
A) Geothermal heat
B) The Sun
C) Tidal forces
D) Earth’s rotation
Correct Answer: B
Explanation: The Sun provides the vast majority of energy that drives Earth’s climate through solar radiation (insolation). Geothermal heat from the interior, tidal forces from the Moon/Sun, and rotational effects contribute only a tiny fraction compared to incoming solar energy.
2. Which layer of Earth is the hottest and is composed mostly of iron and nickel?
A) Crust
B) Mantle
C) Outer core
D) Inner core
Correct Answer: D
Explanation: The inner core is solid, reaches temperatures of ~5,000–6,000°C, and consists primarily of an iron-nickel alloy under extreme pressure. The outer core is liquid iron-nickel; the mantle is mostly silicate rocks; the crust is thinner and composed of lighter rocks.
3. What type of rock forms when magma cools and solidifies?
A) Sedimentary
B) Metamorphic
C) Igneous
D) Fossiliferous
Correct Answer: C
Explanation: Igneous rocks (e.g., granite from intrusive cooling, basalt from extrusive) form directly from the cooling and crystallization of molten magma or lava. Sedimentary rocks form from compacted sediments; metamorphic from heat/pressure alteration of existing rocks.
4. Which process involves the breakdown of rocks into smaller pieces without changing their composition?
A) Erosion
B) Weathering
C) Deposition
D) Lithification
Correct Answer: B
Explanation: Weathering is the in-place breakdown of rock (physical/mechanical weathering keeps composition the same; chemical weathering changes it). Erosion is the transport of weathered material; deposition is settling; lithification turns sediments into rock.
5. At which type of plate boundary do plates slide past each other horizontally?
A) Convergent
B) Divergent
C) Transform
D) Subduction
Correct Answer: C
Explanation: Transform boundaries feature horizontal sliding motion (e.g., San Andreas Fault), often causing earthquakes but no creation or destruction of crust. Convergent involves collision/subduction; divergent involves separation and new crust formation.
6. What causes most earthquakes?
A) Volcanic eruptions
B) Sudden movement along faults
C) Tidal forces
D) Meteor impacts
Correct Answer: B
Explanation: The vast majority of earthquakes occur due to the sudden release of built-up elastic strain energy along faults in the lithosphere. Volcanic earthquakes are secondary; tidal forces and impacts cause rare events.
7. Which gas is most responsible for the greenhouse effect on Earth?
A) Oxygen
B) Nitrogen
C) Carbon dioxide
D) Argon
Correct Answer: C
Explanation: Carbon dioxide (CO₂) is a potent greenhouse gas that traps outgoing infrared radiation, and human emissions have significantly enhanced the natural greenhouse effect. Water vapor is the most abundant but largely natural; oxygen, nitrogen, and argon do not absorb infrared effectively.
8. What is the primary source of energy that drives the water cycle?
A) Geothermal energy
B) Solar radiation
C) Wind
D) Earth’s core heat
Correct Answer: B
Explanation: Solar radiation heats Earth’s surface and oceans, causing evaporation (the starting point of the water cycle). Geothermal energy and core heat play minor roles; wind is a secondary mover of moisture.
9. Which cloud type is associated with thunderstorms and heavy precipitation?
A) Cirrus
B) Stratus
C) Cumulus
D) Cumulonimbus
Correct Answer: D
Explanation: Cumulonimbus clouds are tall, vertically developed thunderstorm clouds with strong updrafts, capable of producing heavy rain, hail, lightning, and severe weather. Cirrus are high and wispy; stratus are low and layered; cumulus are fair-weather puffy clouds.
10. What is the name of the supercontinent that existed approximately 250 million years ago?
A) Gondwana
B) Laurasia
C) Pangaea
D) Rodinia
Correct Answer: C
Explanation: Pangaea (“all Earth”) was the supercontinent that existed roughly 335–175 million years ago (peaking around 250 mya) before breaking apart into modern continents. Gondwana and Laurasia were later fragments; Rodinia was much older (~1 billion years ago).
11. Which layer of the atmosphere contains the ozone layer?
A) Troposphere
B) Stratosphere
C) Mesosphere
D) Thermosphere
Correct Answer: B
Explanation: The ozone layer, which absorbs harmful UV radiation, is located in the stratosphere (about 10–50 km altitude). The troposphere is where weather occurs; mesosphere burns meteors; thermosphere has auroras and high temperatures.
12. What is the process by which plants release water vapor into the atmosphere?
A) Evaporation
B) Condensation
C) Transpiration
D) Precipitation
Correct Answer: C
Explanation: Transpiration is the evaporation of water from plant leaves through stomata as part of photosynthesis and cooling. Evaporation is from open water/soil; condensation forms clouds; precipitation is falling moisture.
13. Which type of rock is most likely to contain fossils?
A) Igneous
B) Metamorphic
C) Sedimentary
D) Extrusive
Correct Answer: C
Explanation: Sedimentary rocks form in layers from deposited sediments (often in water), preserving organisms as fossils (e.g., shale, limestone). Heat in igneous and metamorphic rocks usually destroys organic remains.
14. What is the primary cause of seasons on Earth?
A) Distance from the Sun
B) Earth’s axial tilt
C) Solar flares
D) Moon phases
Correct Answer: B
Explanation: Earth’s 23.5° axial tilt causes varying angles and durations of sunlight throughout the year as it orbits, leading to seasons. Orbital distance varies minimally and does not drive seasonal changes.
15. Which planet has the most moons in our solar system?
A) Jupiter
B) Saturn
C) Uranus
D) Neptune
Correct Answer: B
Explanation: As of current 2026 knowledge, Saturn has the highest number of confirmed moons (over 140+ with recent discoveries), edging out Jupiter.
16. What is the name of the boundary between the crust and the mantle?
A) Moho
B) Gutenberg
C) Lehman
D) Asthenosphere
Correct Answer: A
Explanation: The Mohorovičić discontinuity (Moho) is the seismic velocity boundary separating the crust from the mantle. Gutenberg is core-mantle; Lehman is inner-outer core; asthenosphere is a plastic zone in the upper mantle.
17. Which type of galaxy is the Milky Way?
A) Elliptical
B) Irregular
C) Spiral
D) Lenticular
Correct Answer: C
Explanation: The Milky Way is a barred spiral galaxy with a central bar, disk, spiral arms, and bulge. Elliptical galaxies are oval; irregular have no defined shape; lenticular are disk-like without arms.
18. What causes the auroras (Northern/Southern Lights)?
A) Solar wind interacting with Earth’s magnetic field
B) Lightning in the upper atmosphere
C) Volcanic dust
D) Refraction of moonlight
Correct Answer: A
Explanation: Charged particles in the solar wind are funneled by Earth’s magnetic field toward the poles, exciting atmospheric gases (oxygen/nitrogen) to emit light. Not caused by lightning, dust, or moonlight refraction.
19. Which mineral property is tested using a streak plate?
A) Hardness
B) Luster
C) Color of powder
D) Cleavage
Correct Answer: C
Explanation: Streak is the color of the mineral’s powdered form when rubbed on a streak plate (often different from visible color). Hardness uses Mohs/scratch test; luster is shine type; cleavage is break pattern.
20. What is the primary force responsible for plate movement?
A) Convection in the mantle
B) Earth’s rotation
C) Gravitational pull of the Moon
D) Solar wind
Correct Answer: A
Explanation: Mantle convection (hot material rises, cooler sinks) drives plate motion via slab pull, ridge push, and basal traction. Rotation, lunar gravity, and solar wind have negligible direct effects.
21. Which era is known as the “Age of Dinosaurs”?
A) Cenozoic
B) Mesozoic
C) Paleozoic
D) Precambrian
Correct Answer: B
Explanation: The Mesozoic Era (Triassic, Jurassic, Cretaceous) is called the Age of Dinosaurs due to their dominance. Paleozoic had early life; Cenozoic is the Age of Mammals; Precambrian is pre-complex life.
22. What is the main source of energy for hurricanes?
A) Warm ocean water
B) Jet streams
C) Cold fronts
D) Earth’s core
Correct Answer: A
Explanation: Hurricanes draw energy from latent heat released when warm ocean water (>26.5°C) evaporates, condenses in clouds, and fuels intensification. Jet streams steer them; cold fronts are unrelated; core heat is irrelevant.
23. Which type of star is the Sun?
A) Red giant
B) White dwarf
C) Main sequence
D) Supergiant
Correct Answer: C
Explanation: The Sun is currently a G-type main-sequence star stably fusing hydrogen into helium in its core. Red giants and supergiants are later evolutionary stages; white dwarfs are stellar remnants.
24. What is El Niño associated with?
A) Warmer-than-average Pacific Ocean temperatures
B) Colder-than-average Atlantic temperatures
C) Stronger trade winds
D) Decreased rainfall worldwide
Correct Answer: A
Explanation: El Niño involves weakened trade winds and warmer sea-surface temperatures in the eastern equatorial Pacific, disrupting normal weather patterns (e.g., floods/droughts). Opposite of La Niña; not primarily Atlantic or global rainfall decrease.
25. Which process forms metamorphic rocks?
A) Cooling of magma
B) Heat and pressure on existing rocks
C) Compaction and cementation
D) Weathering and erosion
Correct Answer: B
Explanation: Metamorphic rocks form when existing rocks (protoliths) are altered by intense heat and/or pressure without melting (e.g., slate from shale). Cooling = igneous; compaction/cementation = sedimentary.
26. What is the approximate age of Earth?
A) 4.6 billion years
B) 1.2 billion years
C) 10 million years
D) 65 million years
Correct Answer: A
Explanation: Radiometric dating (e.g., uranium-lead in oldest zircons and meteorites) consistently dates Earth at approximately 4.54–4.6 billion years old.
27. Which is an example of a renewable resource?
A) Coal
B) Solar energy
C) Natural gas
D) Uranium
Correct Answer: B
Explanation: Solar energy is naturally replenished on human timescales. Coal, natural gas, and uranium are non-renewable fossil/nuclear fuels formed over geologic time.
28. What causes tides on Earth?
A) Wind
B) Gravitational pull of the Moon and Sun
C) Earth’s magnetic field
D) Ocean currents
Correct Answer: B
Explanation: Differential gravitational forces from the Moon (primary) and Sun create tidal bulges in oceans. Wind and currents influence local tides but do not cause the fundamental tidal cycle.
29. Which layer of Earth is semi-solid and allows convection?
A) Crust
B) Upper mantle (asthenosphere)
C) Outer core
D) Inner core
Correct Answer: B
Explanation: The asthenosphere (upper mantle) is hot and plastic/semi-molten, allowing slow convection currents that drive plate tectonics. Crust is rigid; outer core is liquid metal; inner core is solid.
30. What is the Big Bang theory?
A) The origin of the universe from a hot, dense state
B) Formation of the solar system
C) Plate tectonics explanation
D) Evolution of life
Correct Answer: A
Explanation: The Big Bang theory describes the universe expanding from an extremely hot, dense state about 13.8 billion years ago, supported by cosmic microwave background, redshift, etc.
31. Which fossil type shows evidence of animal activity (e.g., burrows)?
A) Body fossil
B) Trace fossil
C) Mold fossil
D) Cast fossil
Correct Answer: B
Explanation: Trace fossils (ichnofossils) preserve evidence of behavior like footprints, burrows, or trails. Body fossils are actual remains; mold/cast are impressions/fills of body parts.
32. What is the primary composition of Earth’s inner core?
A) Liquid iron
B) Solid iron and nickel
C) Silicate rocks
D) Magma
Correct Answer: B
Explanation: Despite extreme heat, immense pressure keeps the inner core solid iron-nickel alloy. Outer core is liquid; mantle is silicates; no magma there.
33. Which is NOT a greenhouse gas?
A) Carbon dioxide
B) Methane
C) Oxygen
D) Water vapor
Correct Answer: C
Explanation: Oxygen (O₂) does not absorb infrared radiation significantly. CO₂, CH₄ (methane), and H₂O (water vapor) are major greenhouse gases.
34. What scale measures earthquake magnitude?
A) Beaufort
B) Richter/Moment Magnitude
C) Saffir-Simpson
D) Fujita
Correct Answer: B
Explanation: The Moment Magnitude Scale (modern standard, replacing Richter for large quakes) measures total energy released. Beaufort = wind; Saffir-Simpson = hurricanes; Fujita = tornadoes.
35. Which moon phase occurs when the Moon is between Earth and the Sun?
A) Full Moon
B) New Moon
C) First Quarter
D) Last Quarter
Correct Answer: B
Explanation: New Moon occurs when the Moon is aligned between Earth and Sun, with its dark side facing Earth (unlit from our view). Full Moon is opposite alignment.
36. What is the primary cause of volcanic activity at subduction zones?
A) Diverging plates
B) Melting of subducting crust
C) Transform motion
D) Hot spots
Correct Answer: B
Explanation: Water released from the subducting plate lowers the melting point of mantle rock above, generating magma that rises to form volcanoes (e.g., Ring of Fire).
37. Which is the hottest layer of Earth’s atmosphere?
A) Troposphere
B) Stratosphere
C) Mesosphere
D) Thermosphere
Correct Answer: D
Explanation: The thermosphere absorbs intense solar X-rays and UV, reaching temperatures of thousands of °C (though thin air means low heat content).
38. What type of rock is marble?
A) Igneous
B) Sedimentary
C) Metamorphic
D) Extrusive
Correct Answer: C
Explanation: Marble is metamorphic rock formed from limestone (sedimentary) recrystallized under heat and pressure, often used for sculptures due to its texture.
39. Which force causes winds to curve due to Earth’s rotation?
A) Gravity
B) Friction
C) Coriolis effect
D) Pressure gradient
Correct Answer: C
Explanation: The Coriolis effect is the apparent deflection of moving objects (like air masses) due to Earth’s rotation—right in Northern Hemisphere, left in Southern.
40. What is a black hole?
A) A region where gravity is so strong light cannot escape
B) A dying star
C) A comet’s nucleus
D) A neutron star
Correct Answer: A
Explanation: A black hole is defined by its event horizon, beyond which gravity prevents light/anything from escaping, typically formed from collapsed massive stars.
41. Which mineral is the hardest on the Mohs scale?
A) Quartz
B) Diamond
C) Talc
D) Gypsum
Correct Answer: B
Explanation: Diamond ranks 10 on the Mohs hardness scale (hardest known natural mineral). Talc = 1 (softest); gypsum = 2; quartz ≈ 7.
42. What is the main difference between weather and climate?
A) Weather is short-term; climate is long-term average
B) Weather is global; climate is local
C) Weather involves only temperature
D) Climate changes daily
Correct Answer: A
Explanation: Weather refers to short-term atmospheric conditions (hours to weeks); climate is the long-term average pattern (typically 30+ years) of weather in a region.
43. Which planet is known as the “Red Planet”?
A) Venus
B) Mars
C) Jupiter
D) Mercury
Correct Answer: B
Explanation: Mars appears red due to iron oxide (rust) covering its surface soil and rocks.
44. What causes the seasons to be opposite in the Northern and Southern Hemispheres?
A) Earth’s distance from Sun
B) Tilt of Earth’s axis
C) Moon’s orbit
D) Solar wind
Correct Answer: B
Explanation: The 23.5° axial tilt means when the Northern Hemisphere tilts toward the Sun (summer), the Southern tilts away (winter), and vice versa.
45. Which is an example of chemical weathering?
A) Frost wedging
B) Oxidation of iron
C) Abrasion by wind
D) Root wedging
Correct Answer: B
Explanation: Oxidation (e.g., iron rusting) is a chemical reaction altering mineral composition. Frost wedging, abrasion, and root wedging are physical/mechanical processes.
46. What is the primary source of Earth’s magnetic field?
A) Crustal rocks
B) Motions in the outer core
C) Solar wind
D) Mantle convection
Correct Answer: B
Explanation: The geodynamo—convection of liquid iron-nickel in the outer core—generates Earth’s magnetic field through electric currents.
47. Which type of plate boundary creates new oceanic crust?
A) Convergent
B) Divergent
C) Transform
D) Subduction
Correct Answer: B
Explanation: Divergent boundaries (e.g., mid-ocean ridges) create new oceanic crust through seafloor spreading as magma rises and solidifies.
48. What is a supernova?
A) A star’s explosive death
B) Birth of a star
C) Collision of galaxies
D) Formation of a black hole
Correct Answer: A
Explanation: A supernova is the catastrophic explosion at the end of a massive star’s life, dispersing heavy elements into space (can leave neutron star or black hole remnant).
49. Which layer of Earth contains the lithosphere?
A) Crust and uppermost mantle
B) Lower mantle
C) Outer core
D) Inner core
Correct Answer: A
Explanation: The lithosphere is the rigid outer shell (~100 km thick) comprising the crust and brittle uppermost mantle, broken into tectonic plates.
50. What evidence supports the theory of plate tectonics?
A) Matching coastlines and fossils
B) GPS measurements of plate motion
C) Magnetic stripes on seafloor
D) All of the above
Correct Answer: D
Explanation: Multiple independent lines converge: jigsaw-fit continents and matching fossils (e.g., Mesosaurus), seafloor spreading via magnetic reversal stripes, direct GPS tracking of plate movement, and more.
