Astronomy Chapter 9

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

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

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

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.

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

Size: same as the Moon. Distance from Sun: same as Mars. Rotation rate: once every 10 days.

which internal energy source produces heat by converting gravitational potential energy into thermal energy

accretion and differentiation

the three principal sources of internal heat of terrestrial planets are

accretion, differentiation and radioactivity

what kind of surface features may result from tectonics?

all of the above

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

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

What drives the motion of the tectonic plates on Earth?

convection cells in the mantle

from center to surface, which of the following correctly lists the interior layers of a terrestrial world?

core, mantle, crust

which two properties are most important in determining the surface temperature of a planet

distance from the Sun and atmosphere

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

which of the terrestrial worlds has the strongest magnetic field

earth

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

which internal heat source still generates heat within the terrestrial worlds today?

heat from radioactive decay

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

in general, which things below are affected by a magnetic field?

impact cratering, volcanism, tectonics and erosion

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, or the lithosphere?

internal temperature

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 is the result of countless tiny impacts by small particles striking the moon

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 km across

which of the following has virtually no effect on the structure of a planet?

its magnetic field

which of the following most likely explain why Venus does not have a strong magnetic field?

its rotation is too slow

which of the following most likely explains why Venus does not have a global magnetic field like Earth?

its rotation is too slow

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 density?

its size

which of the following is the underlying reason why Venus has so little wind erosion?

its slow rotation

what is the fundamental reason that Mars, unlike Earth, has become virtually geologically dead?

its small size compared to Earth

why does the Moon have a layer of powdery "soil" on its surface?

its the result of gradual erosion by micrometeorites striking the Moon

Valles Marineris is a

large canyon on Mars

how did the lunar maria form?

large impacts fractures the Moon's lithosphere, allowing lava to fill the impact basins

which of the following does not have a major effect in shaping planetary surfaces

magnetism

Which two factors are most important to the existence of plate tectonics on Earth?

mantle convection and a thin lithosphere

Most of the Moon's surface is densely covered with craters, but we find relatively few craters with lunar maria. What can we conclude?

maria formed after the heavy bombardment ended

the terrestrial planet cores contain mostly metal because

metals sank to the center during a time when the interiors were molten throughout

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

The polar caps on Mars are composed of

mostly solid carbon dioxide and some water ice

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

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

what are the two geological features that appear to set Earth apart from all the other terrestrial worlds?

plate tectonics and widespread erosion

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

many scientists suspect that Venus has a stronger and thicker lithosphere than Earth. If this is true, which of the following could explain?

the high surface temperature that has "baked out" all the liquid water from Venus's crust and mantle

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 is not generally true of all the terrestrial world lithospheres?

the lithosphere is broken into a set of large plated that float upon the softer rock below

Under what circumstances can differentiation occur in a planet?

the planet must have a molten interior

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 Precival Lowell

what observational evidence supports the idea that Mercury once shrank by some 20 kilometers in radius?

the presence of many long, tall cliffs

Which of the following does not provide evidence that Mars once had flowing?

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

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

the lithosphere of a planet is the layer that consists of

the rigid rocky material of the crust and uppermost portion of the mantle

Why are there fewer large craters on the seafloor than on the continents?

the seafloor crust is younger than the continental crust

when we see a region of a planet that is not as heavily cratered as other regions, we conclude

the surface in the region is younger than the surface in more heavily cratered regions

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

Which two geological processes appear to have been most important in shaping the present surface of venus?

volcanoes and tectonics

which of the following is an example of convection

warm air expanding and rising while cooler air contracts and fall

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

Rank the five terrestrial worlds in order of size from smallest to largest

Moon, Mercury, Mars, Venus, Earth

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 of the following worlds have the thinnest lithospheres?

Earth and Venus

which of the following places is the result of volcanoes erupting over a hot spot in the mantle?

Hawaii

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?

Mar's interior has cooled so much its molten core layer no longer undergoes convection

which of the following show evidence of ancient river bed?

Mars

Spacecraft have landed on all the terrestrial worlds except

Mercury

all of 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 basic requirements for a terrestrial world to have a global magnetic field?

a core layer of molten, convecting material and sufficiently rapid rotation

How fast do plates move on Earth?

a few centimeters per year

on average, how fast do the plates move on Earth

a few centimeters per year

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

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

Olympus Mons is

a huge shield volcano on Mars

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

a terrestrial world's lithosphere is

a layer of relatively strong, rigid rock, encompassing the crust and part of the mantle

in the context of plate tectonics, what is a subduction zone

a place where a seafloor plate is sliding under a continental plate

Olympus Mons is

a shield volcano on Mars

what is basalt

a type of rock that makes relatively low-viscosity lava

which of the following best describes the lunar maria?

relatively smooth, flat plains on the Moon

how does seafloor crust differ from continental crust

seafloor crust is thinner, younger and higher in density

how does seafloor crust differ from continental crust?

seafloor crust is thinner, younger, and higher in density

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: same as the moon. distance from sun: same as mars. rotation rate: once every 10 days.

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 Carolis 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

which of the following describes impact cratering?

the excavation of bowl-shaped depressions by asteroids or comets striking a planet's surface

which of the following is not an example of tectonics?

the gradual disappearance of a crater rim as a result of wind and rain

what are the circumstances under which convection can occur in a substance?

when the substance is strongly heated from underneath

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