Astronomy Chapter 9
How large is an impact crater compared to the size of the impactor?
10 times larger
How long, approximately, do geologists estimate it takes for the entire seafloor to be replaced due to plate tectonics?
200 million years
Some of the oldest continental crust on Earth lies in
Northeastern Canada
How does seafloor crust differ from continental crust?
Seafloor crust is thinner, younger, and higher in density.
The three principal sources of internal heat of terrestrial planets are
accretion, differentiation, and radioactivity.
What are the conditions necessary for a terrestrial planet to have a strong magnetic field?
both a molten metallic core and reasonably fast rotation
How have we been able to construct detailed maps of surface features on Venus?
by using radar from spacecraft that were sent to orbit Venus
The "core", "mantle", and "crust" of a planet are defined by differences in their
composition
The main process by which heat flows upward through the lithosphere is
conduction
What drives the motion of the tectonic plates on Earth?
convection cells in the mantle
Which two properties are most important in determining the surface temperature of a planet?
distance from the Sun and atmosphere
Which of the following is not evidence for plate tectonics on Earth?
existence of volcanoes
When we say that a liquid has a high viscosity, we mean that it
flows slowly like honey
Steep-sided "stratovolcanoes" are made from lava that
has a high viscosity
Shallow-sloped "shield volcanoes" are made from lava that
has a medium viscosity
Volcanism is more likely on a planet that
has high internal temperatures
A planet is most likely to have tectonic activity if it has
high internal temperature
Ridges in the middle of the ocean are places where
hot mantle material rises upward and spreads sideways, pushing the plates apart.
Heat escapes from a planet's surface into space by thermal radiation. Planets radiate almost entirely in the wavelength range of the
infrared
What is the most important factor that determines the thickness, and therefore strength, of the lithosphere?
internal temperature
Which of the following has virtually no effect on the structure of a planet?
its magnetic field
"Valles Marineris" is a
large canyon on Mars
Which of the following does not have a major effect in shaping planetary surfaces?
magnetism
The terrestrial planet cores contain mostly metal because
metals sank to the center during a time when the interiors were molten throughout.
The polar caps on Mars are composed of
mostly solid carbon dioxide and some water ice.
Deep trenches in the ocean mark places where
one plate slides under another, returning older crust to the mantle.
What process has shaped Earth's surface more than any other?
plate tectonics
The geysers and hot springs of Yellowstone National Park result from
plumes of hot mantle rising in a hot spot within a plate.
Which internal energy source is the most important in continuing to heat the terrestrial planets today?
radioactivity
Which of the following regions was the result of plumes of hot mantle rising in a hot spot within a plate?
the islands of Hawaii
Which of the following does not provide evidence that Mars once had flowing water?
the presence of vast canals discovered in the late 1800s by Giovanni Schiaparelli and mapped by Percival Lowell
What is "differentiation" in planetary geology?
the process by which gravity separates materials according to density
The "lithosphere" of a planet is the layer that consists of
the rigid rocky material of the crust and uppermost portion of the mantle.
When we see a region of a planet that is not as heavily cratered as other regions, we conclude that
the surface in the region is younger than the surface in more heavily cratered regions.
Which of the following describes erosion?
the wearing down or building up of geological features by wind, water, ice, and other phenomena of planetary weather
Which two geological processes appear to have been most important in shaping the present surface of Venus?
volcanoes and tectonics
The relatively few craters that we see within the lunar maria
were formed by impacts that occurred after those that formed most of the craters in the lunar highlands.
What kind of surface features may result from tectonics?
All of the above A) mountains B) valleys C) volcanos D) cliffs
Which internal energy source produces heat by converting gravitational potential energy into thermal energy?
Both A and B A) accretion B) differentiation
Spacecraft have landed on all the terrestrial worlds except
Mercury
Rank the five terrestrial worlds in order of size from smallest to largest.
Moon, Mercury, Mars, Venus, Earth
Why is continental crust lower in density than seafloor crust?
Continental crust is made from remelted seafloor crust and therefore only the lower-density material rises to form it.
Which of the terrestrial worlds has the strongest magnetic field?
Earth
Which of the following worlds have the thinnest lithospheres?
Earth and Venus
Why does Earth have the strongest magnetic field among the terrestrial worlds?
It is the only one that has both a partially molten metallic core and reasonably rapid rotation.
Which of the following best describes "convection"?
It is the process in which warm material expands and rises while cool material contracts and falls.
Why does the Moon have a layer of powdery "soil" on its surface?
It's the result of gradual erosion by micrometeorites striking the Moon.
Which of the following most likely explains why Venus does not have a strong magnetic field?
Its rotation is too slow.
How did the lunar maria form?
Large impacts fractured the Moon's lithosphere, allowing lava to fill the impact basins.
Which of the following show evidence of ancient river beds?
Mars
Under what circumstances can differentiation occur in a planet?
The planet must have a molten interior.
Why are there fewer large craters on the seafloor than on the continents?
The seafloor crust is younger than the continental crust.
Which of the following best describes why the smaller terrestrial worlds have cooler interiors than the larger ones?
They have relatively more surface area compared to their volumes.
Why do we think Mercury has so many tremendous cliffs?
They were probably formed by tectonic stresses when the entire planet shrank as its core cooled.
How fast do plates move on Earth?
a few centimeters per year
What is "basalt"?
a type of rock that makes relatively low-viscosity lava
"Olympus Mons" is a
shield volcano on Mars
The "Caloris Basin" on Mercury covers a large region of the planet, but few smaller craters have formed on top of it. From this we conclude that
the Caloris Basin formed toward the end of the solar system's period of heavy bombardment.
What type of stresses broke Earth's lithosphere into plates?
the circulation of convection cells in the mantle, which dragged against the lithosphere
Which of the following describes tectonics?
the disruption of a planet's surface by internal stresses
Which of the following describes volcanism?
the eruption of molten rock from a planet's interior to its surface
Which of the following describes impact cratering?
the excavation of bowl-shaped depressions by asteroids or comets striking a planet's surface
What are the circumstances under which convection can occur in a substance?
when the substance is strongly heated from underneath