Introduction to Environmental Geology, 5e (Keller)
Chapter 12 Impact of Extraterrestrial Objects
12.1 Multiple-Choice Questions
1) In 1908, the Tunguska River Valley in Siberia experienced
A) a nuclear explosion
B) an aerial burst of a meteor
C) a major earthquake
D) a volcanic eruption
2) A meteoroid is
A) a small particle of an asteroid
B) a giant asteroid
C) a streak of light across the sky
D) a meteor that has struck the Earth’s surface
3) A meteor is
A) a small comet
B) a large meteoroid
C) a meteoroid that has entered the Earth’s atmosphere
D) a meteoroid that strikes the Earth’s surface
4) A meteorite is
A) a small comet
B) a large meteoroid
C) a meteoroid that has entered the Earth’s atmosphere
D) a meteoroid, asteroid, or comet that strikes the Earth’s surface
5) In 1994, the comet Shoemaker-Levy 9 collided with
A) Earth
B) Mars
C) Moon
D) Jupiter
6) A meteorite impact crater can be distinguished from a volcanic crater through the presence of
A) volcanic rock
B) high pressure metamorphic minerals
C) dust surrounding the crater
D) a raised crater rim
7) Why are impact craters more common on the Moon and Mars than on Earth?
A) the Moon and Mars have thinner atmospheres
B) more meteoroids approach the Moon and Mars
C) the Moon and Mars consist of stronger rock that preserves craters better
D) meteorites striking Earth are typically larger
8) The Cretaceous-Tertiary mass extinction was apparently caused by a meteorite that struck
A) Yucatan Peninsula
B) Pacific coast of Canada
C) Europe
D) Australia
9) Why is the probability of dying from a meteorite impact greater than that of dying in an
automobile accident?
A) because fatal meteorite impacts are likely to occur very frequently
B) because there is a high probability that any person will be hit directly by a meteorite
C) because a large meteorite impact would cause a very high number of fatalities
D) because there are millions of meteoroids in near-Earth orbit
10) What element was found to be enriched in a thin clay layer marking the Cretaceous-Tertiary
boundary at several sites around the world?
A) calcium
B) uranium
C) iridium
D) niobium
11) How big was the meteorite that apparently caused the Cretaceous-Tertiary mass extinction?
A) 1 km
B) 10 km
C) 100 km
D) 1000 km
12) What would be the principal option for preventing a catastrophic meteorite impact, once a
threatening object was identified?
A) changing the orbit of the object with small nuclear explosions
B) breaking the object into smaller pieces with nuclear explosions
C) evacuate the potentially affected area
D) constructing a physical shield around Earth
13) Why are ancient impact craters difficult to identify on Earth?
A) they typically have been eroded or infilled with younger sediments
B) impact craters on Earth are smaller than those on the Moon or Mars
C) they typically lack shock metamorphic minerals
D) there have been very few meteorite impacts on Earth
14) Why do some asteroids leave the asteroid belt and cross the orbits of Earth and other solar
system bodies?
A) The gravity of Earth and other bodies pull the asteroids out of the asteroid belt.
B) Asteroids collide in the asteroid belt and some asteroids are diverted into other orbits.
C) Comets passing through the asteroid belt pull asteroids away.
D) The asteroid belt is slowly expanding with time, into orbits of Earth and other bodies.
15) What is an aerial burst?
A) an explosion in the asteroid belt that sends asteroids hurtling toward Earth
B) a secondary explosion above an impact crater, occurring after impact
C) a meteor bursting into many smaller pieces when bombarded with nuclear weapons
D) an explosion of a meteor entering the Earth’s atmosphere
1) The Tunguska event resulted from impact of a large meteorite.
2) Most asteroids are found between Mars and Jupiter.
3) Comets typically orbit the sun at the distance of Neptune.
4) An asteroid or comet that strikes the Earth’s surface is called a meteor.
5) The shock wave resulting from meteorite impact causes metamorphism and melting of rocks
at and near the Earth’s surface.
6) The mass extinction at the Permian-Triassic transition definitely resulted from meteorite
impact.
7) The Chicxulub impact crater in the Yucatan is an easily recognizable crater.
8) The Chicxulub impact crater was the first evidence to suggest that a meteorite impact caused
the Cretaceous-Tertiary mass extinction.
9) The Tunguska event would likely have killed millions of people if it had happened over a
heavily populated area.
10) There is very little chance that we will know of a likely catastrophic meteorite impact ahead
of time.
11) Impact of a large extraterrestrial object is probable within the next century.
12) Blowing a threatening extraterrestrial object into small pieces would likely increase the
hazard to Earth.
13) The Cretaceous-Tertiary impact event was first discovered through the chemistry of
sediments.
14) Asteroids are concentrated in the Oort Cloud, beyond Neptune.
12.3 Short Answer Questions
1) An aerial burst occurred in the Tunguska River valley of ________ in 1908.
2) A meteoroid that enters the Earth’s atmosphere is called a(n) ________.
3) A(n) ________ is a bowl-shaped depression caused by a meteorite striking the Earth’s surface.
4) Because of a thinner ________, there are more impact craters on the Moon than on Earth.
5) The impact crater resulting from the Cretaceous-Tertiary meteorite impact was found in the
country of ________.
6) An anomaly of the element ________ marks the Cretaceous-Tertiary boundary in several
locations around the world.
7) The elimination of a large proportion of species on Earth is called a(n) ________.
8) The ________ of dying from a meteorite impact is greater than that of dying in an auto
accident.
9) One option for preventing a major meteorite impact would be to nudge the object into a
different orbit using ________.
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10) The meteorite that struck the Yucatan Peninsula was about ________ kilometers in diameter.
11) A(n) ________ event is characterized by the sudden loss of large numbers of plants and
animals relative to the number of new species being added.
12) The extinction of large mammals at the end of the ________ Epoch may have been caused
by a meteorite.
13) Two government projects are tracking ________ that might become threats to Earth.