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