Geology 109 Exam 1 Questions Answered Correctly Latest Update 2025-2026
Which of the following is involved in collisional accretion?
a. The selective condensation of elements at different temperatures.
b. The aggregation of planetismals when they impact one another.
c. The hydrodynamic collapse of nebular gases.
d. The gradual change of the gravitational constant. - Answers B
Which of the following are true about planetary accretion? (Select all that apply.)
a. As these particles accreted, the planets became hot as kinetic energy was converted to
thermal energy.
b. The planets grew larger and larger via repeated impact.
c. The planets became internally differentiated to different degrees.
d. The particles that accreted to form the planets were in orbit around the Sun. - Answers a, b, c,
d
When did the planets form?
A. The planets formed before the Sun and were then captured by its large gravity.
B. The planets formed about the same time as the Sun in a relatively short period of time only a
few million years long.
C. The planets started to accrete about the same time as the Sun, but then grew slowly over a
period of about two billion years.
D. The planets are a young feature of the Solar System forming only a few thousands of years
ago. - Answers B
Which of these is evidence for planetary accretion?
A. The heavily cratered surfaces of the Moon and other planetary bodies.
B. The absence of atmospheres on the Moon and Mercury
C. The rings of Saturn.
D. The abundance of water on Earth. - Answers A
How did the giant outer planets obtain their thick atmospheres?
,A. By degassing from their icy interiors.
B. By collapse of nebular gas onto a protoplanet's icy core.
C. By collection of gas swept into the outer solar system during the T-Tauri stage of the Sun's
development.
D. As the nebula cooled, the volatile gases condensed onto the planets. - Answers B
Large planetary bodies failed to accrete in some parts of the solar system and did not sweep
their neighborhoods clear of debris. Select the two most prominent zones of this "debris."
A. between Venus and Earth
B. between Mars and Jupiter
C. between Uranus and Neptune
D. beyond Neptune - Answers B, D
Which of the following are characteristics of the orbits of the objects that accrete to make
planets? (Select all that apply.)
A. Their orbits form a flattened disk shape.
B. Their orbits form a spherical zone centered on the star.
C. Their orbits define an elliptical zone tilted about 90° to the eliptic.
D. They orbit in the equatorial plane (ecliptic) of the star. - Answers A, D
The spin axes of some planets are tilted relative to the plane in which most orbit. What could
have caused this?
A. The impact of a large object late in the history of accretion changed the spin.
B. More accretion occurred on one side of the planet than on the other and it tipped on its side.
C. These planets were probably captured from a passing star.
D. With the passage of time, the spin axis of a planet starts to tilt to one side. - Answers A
Think about the process of planetary accretion. Which statement best describes our current
ideas about the rate of impact cratering in the inner solar system?
A. The rates of meteorite bombardment steadily declined after the age of accretion.
B. The rate of bombardment increased with time to reach its maximum today.
, C. Initially, the rate declined smoothly, but there was a later episode of heavy bombardment
followed by resumption of the decline.
D. Initially, the rate increased smoothly, but there was an episode of much lower impact rates
followed by a resumption of the increase. - Answers C
Which of the following best describes the orbital evolution of the planets in our solar system
according to the Nice Model?
A. The orbits of the planets have been more or less the way they are today for over 4.5 billion
years.
B. The orbits of the inner planets were once much closer to the Sun than they are now and they
have slowly moved outward by centripetal forces.
C. Earth, Mars, and Venus formed in the outer solar system, but they have slowly spiraled
inward to their present orbits near the Sun.
D. The orbits of the outer planets changed significantly about 3.9 billion years ago as Uranus
and Neptune moved outward from the Sun. - Answers D
Which is true about our current understanding of extrasolar planets (exoplanets)?
A. Exoplanets are very rare and only found around very old stars.
B. Exoplanets are common and found around many different types of stars.
C. Exoplanets are only found around planets with sizes similar to the Sun.
D. Exoplanets are so far away, we don't know how many there might be. - Answers B
In general , large planets cool _____________________.
A. during core formation
B. before a lithosphere can form
C. more rapidly than small planets of similar composition
D. more slowly than small planets of similar compositions - Answers D
Important sources of planetary heat include all of the following except _______________.
A. accretion
B. core formation
C. tidal heating
Which of the following is involved in collisional accretion?
a. The selective condensation of elements at different temperatures.
b. The aggregation of planetismals when they impact one another.
c. The hydrodynamic collapse of nebular gases.
d. The gradual change of the gravitational constant. - Answers B
Which of the following are true about planetary accretion? (Select all that apply.)
a. As these particles accreted, the planets became hot as kinetic energy was converted to
thermal energy.
b. The planets grew larger and larger via repeated impact.
c. The planets became internally differentiated to different degrees.
d. The particles that accreted to form the planets were in orbit around the Sun. - Answers a, b, c,
d
When did the planets form?
A. The planets formed before the Sun and were then captured by its large gravity.
B. The planets formed about the same time as the Sun in a relatively short period of time only a
few million years long.
C. The planets started to accrete about the same time as the Sun, but then grew slowly over a
period of about two billion years.
D. The planets are a young feature of the Solar System forming only a few thousands of years
ago. - Answers B
Which of these is evidence for planetary accretion?
A. The heavily cratered surfaces of the Moon and other planetary bodies.
B. The absence of atmospheres on the Moon and Mercury
C. The rings of Saturn.
D. The abundance of water on Earth. - Answers A
How did the giant outer planets obtain their thick atmospheres?
,A. By degassing from their icy interiors.
B. By collapse of nebular gas onto a protoplanet's icy core.
C. By collection of gas swept into the outer solar system during the T-Tauri stage of the Sun's
development.
D. As the nebula cooled, the volatile gases condensed onto the planets. - Answers B
Large planetary bodies failed to accrete in some parts of the solar system and did not sweep
their neighborhoods clear of debris. Select the two most prominent zones of this "debris."
A. between Venus and Earth
B. between Mars and Jupiter
C. between Uranus and Neptune
D. beyond Neptune - Answers B, D
Which of the following are characteristics of the orbits of the objects that accrete to make
planets? (Select all that apply.)
A. Their orbits form a flattened disk shape.
B. Their orbits form a spherical zone centered on the star.
C. Their orbits define an elliptical zone tilted about 90° to the eliptic.
D. They orbit in the equatorial plane (ecliptic) of the star. - Answers A, D
The spin axes of some planets are tilted relative to the plane in which most orbit. What could
have caused this?
A. The impact of a large object late in the history of accretion changed the spin.
B. More accretion occurred on one side of the planet than on the other and it tipped on its side.
C. These planets were probably captured from a passing star.
D. With the passage of time, the spin axis of a planet starts to tilt to one side. - Answers A
Think about the process of planetary accretion. Which statement best describes our current
ideas about the rate of impact cratering in the inner solar system?
A. The rates of meteorite bombardment steadily declined after the age of accretion.
B. The rate of bombardment increased with time to reach its maximum today.
, C. Initially, the rate declined smoothly, but there was a later episode of heavy bombardment
followed by resumption of the decline.
D. Initially, the rate increased smoothly, but there was an episode of much lower impact rates
followed by a resumption of the increase. - Answers C
Which of the following best describes the orbital evolution of the planets in our solar system
according to the Nice Model?
A. The orbits of the planets have been more or less the way they are today for over 4.5 billion
years.
B. The orbits of the inner planets were once much closer to the Sun than they are now and they
have slowly moved outward by centripetal forces.
C. Earth, Mars, and Venus formed in the outer solar system, but they have slowly spiraled
inward to their present orbits near the Sun.
D. The orbits of the outer planets changed significantly about 3.9 billion years ago as Uranus
and Neptune moved outward from the Sun. - Answers D
Which is true about our current understanding of extrasolar planets (exoplanets)?
A. Exoplanets are very rare and only found around very old stars.
B. Exoplanets are common and found around many different types of stars.
C. Exoplanets are only found around planets with sizes similar to the Sun.
D. Exoplanets are so far away, we don't know how many there might be. - Answers B
In general , large planets cool _____________________.
A. during core formation
B. before a lithosphere can form
C. more rapidly than small planets of similar composition
D. more slowly than small planets of similar compositions - Answers D
Important sources of planetary heat include all of the following except _______________.
A. accretion
B. core formation
C. tidal heating
