The cores of the terrestrial worlds are made mostly of metal because ______.
metals sunk to the centers a long time ago when the interiors were molten throughout
Which of the following is not generally true of all the terrestrial world lithospheres?
The lithosphere is broken into a set of large plates that float upon the softer rock below.
Which internal heat source still generates heat within the terrestrial worlds today?
Heat from radioactive decay.
The reason that small planets tend to lose interior heat faster than larger planets is essentially the same as the reason that ________.
a large baked potato takes longer to cool than a small baked potato
Suppose we had a device that allowed us to see Earth’s interior. If we looked at a typical region of the mantle, what would we see happening?
not much – on human time scales, the mantle looks like solid rock
Recent evidence suggests that Mars once had a global magnetic field. Assuming this is true, which of the following could explain why Mars today lacks a global magnetic field like that of Earth?
Mars’s interior has cooled so much that its molten core layer no longer undergoes convection.
Which of the following most likely explains why Venus does not have a global magnetic field like Earth?
Its rotation is too slow.
You discover an impact crater that is 10 kilometers across. Which of the following can you conclude?
It was created by the impact of an object about 1 kilometer across.
Most of the Moon’s surface is densely covered with craters, but we find relatively few craters within the lunar maria. What can we conclude?
The maria formed after the heavy bombardment ended.
Which of the following is the underlying reason why Venus has so little wind erosion?
its slow rotation
Which of the following best describes the geological histories of the Moon and Mercury?
Early in their histories, they suffered many impacts and experienced some volcanism and tectonics, but they now have little geological activity at all.
Many scientists suspect that Venus has a stronger and thicker lithosphere than Earth. If this is true, which of the following could explain it?
The high surface temperature that has “baked out” all the liquid water from Venus’s crust and mantle.
All the following statements about Venus are true. Which one offers evidence of a global repaving about a billion years ago?
Venus has relatively few impact craters and these craters are distributed fairly evenly over the entire planet.
What are the two geological features that appear to set Earth apart from all the other terrestrial worlds?
plate tectonics and widespread erosion
Why are there fewer large impact craters on the Earth’s seafloor than on the continents?
Seafloor crust is younger than continental crust, so it has had less time in which to suffer impacts.
Why is Earth’s continental crust lower in density than seafloor crust?
Continental crust is made as the lowest-density seafloor crust melts and erupts to the surface near subduction zones.
Which two factors are most important to the existence of plate tectonics on Earth?
mantle convection and a thin lithosphere
What’s the fundamental reason that Mars, unlike the Earth, has become virtually geologically dead?
its small size compared to Earth
Based on all we know about the terrestrial worlds, what single factor appears to play the most important role in a terrestrial planet’s geological destiny?
The choices below describe four hypothetical planets. Which one would you expect to have the hottest interior? (Assume the planets orbit a star just like the Sun and that they are all the same age as the planets in our solar system.)
Size: twice as big as Earth. Distance from Sun: same as Mercury. Rotation rate: once every 6 months.
The choices below describe four hypothetical planets. Which one’s surface would you expect to be most crowded with impact craters? (Assume the planets orbit a star just like the Sun and that they are all the same age as the planets in our solar system.)
Size: same as the Moon. Distance from Sun: same as Mars. Rotation rate: once every 10 days.
The choices below describe four hypothetical planets. Which one would you expect to have the most features of erosion? (Assume the planets orbit a star just like the Sun and that they are all the same age as the planets in our solar system.)
Size: same as Venus. Distance from Sun: same as Mars. Rotation rate: once every 25 hours.
Suppose we use a baseball to represent Earth. On this scale, the other terrestrial worlds (Mercury, Venus, the Moon, and Mars) would range in size approximately from that of ______.
a golf ball to a baseball
From center to surface, which of the following correctly lists the interior layers of a terrestrial world?
Core, mantle, crust.
What do we mean when we say that the terrestrial worlds underwent differentiation?
When their interiors were molten, denser materials sank toward their centers and lighter materials rose toward their surfaces.
A terrestrial world’s lithosphere is ________.
a layer of relatively strong, rigid rock, encompassing the crust and part of the mantle
The major processes that heat the interiors of the terrestrial worlds are:
(1) Heat deposited as the planets were built from planetesimals; (2) heat deposited as the planets underwent differentiation; (3) heat released by radioactive decay.
Which of the following is an example of convection?
Warm air expanding and rising while cooler air contracts and fall.
What are the basic requirements for a terrestrial world to have a global magnetic field?
A core layer of molten, convecting material and sufficiently rapid rotation.
In general, which things below are affected by a magnetic field?
Charged particles or magnetized materials (such as iron).
The processes responsible for virtually all surface geology are _________.
impact cratering, volcanisms, tectonics, and erosion
Which of the following best describes the lunar maria?
relatively smooth, flat plains on the Moon
In the context of planetary geology, what do we mean by outgassing?
the release by volcanism of gases that had been trapped in a planetary interior
Which of the following is not an example of tectonics?
The gradual disappearance of a crater rim as a result of wind and rain.
Why does the Moon have a layer of “powdery soil” on its surface?
It is the result of countless tiny impacts by small particles striking the Moon.
What observational evidence supports the idea that Mercury once shrank by some 20 kilometers in radius?
the presence of many long, tall cliffs
Olympus Mons is ______.
a huge shield volcano on Mars
Which of the following does not provide evidence that Mars once had abundant liquid water on its surface?
the presence of canali, discovered in the late 1800s by Giovanni Schiaparelli and mapped by Percival Lowell.
Based on its surface features, the most important event on Venus in the past billion years or so was _______.
a global “repaving” that erased essentially all the surface features that had existed earlier.
On average, how fast do the plates move on the Earth?
a few centimeters per year
How does seafloor crust differ from continental crust?
Seafloor crust is thinner, younger, and higher in density.
In the context of plate tectonics, what is a subduction zone?
A place where a seafloor plate is sliding under a continental plate.
Which of the following places is the result of volcanoes erupting over a hot spot in the mantle?