Geol 101: Physical Geology
PAST EXAM QUESTIONS
LECTURE 18: GEOLOGIC TIME II
18. The correct arrangement of the different types of geologic time divisions, from longest to shortest, is:
A. epochs, periods, eras, eons
B. periods, eons, epochs, eras
C. eons, eras, periods, epochs
D. eons, epochs, eras, periods
E. eras, periods, epochs, eons
18. The time divisions in the Geologic Column that represent the longest lengths of time are called:
A. eras
B. epochs
C. eons
D. periods
E. years
18. The Hadean, Archean, and Proterozoic eons are collectively called the:
A. Phanerozoic
B. Mesozoic
C. Holocene
D. Precambrian
E. days of yore
18. Which of the eons listed below is NOT considered to be part of the Precambrian?
A. Phanerozoic
B. Proterozoic
C. Archean
D. Hadean
E. Cambrian
18. The only eon that has been subdivided into eras and periods in the geologic column based on the types of fossils
present in the rocks is the __________ Eon.
A. Phanerozoic
B. Archean
C. Hadean
D. Paleozoic
E. Precambrian
18. Cambrian, Ordovician, Silurian, Devonian, Carboniferous (Camels Only Sit Down Carefully). What comes next?
A. Triassic then Permian
B. Tertiary then Quaternary
C. Cretaceous then Tertiary
D. Permian then Triassic
E. Jurassic then Cretaceous
18. Cambrian, Ordovician, Silurian, Devonian, Carboniferous (Camels Only Sit Down Carefully). What comes next?
A. Triassic
B. Tertiary
C. Quaternary
D. Permian
E. Jurassic
18. If camels only sit down carefully, perhaps their joints creak. So which of the following is true?
A. the Cambrian comes after the Cretaceous
B. the Silurian comes after the Permian
C. the Carboniferous comes after the Triassic
D. the Ordovician comes before the Silurian
E. the Devonian comes before the Cambrian
18. The Pliocene epoch was followed by the ________ epoch, when the Mediterranean filled up again, and an ice
age began.
A. Holocene
B. Paleocene
C. Pleistocene
D. Oligocene
E. Tertiary
18. The Holocene is an example of a/an:
A. era
B. epoch
C. eon
D. period
E. absolute age
18. The epoch that we currently live in is called the:
A. Holocene
B. Pleistocene
C. Pliocene
D. Miocene
E. Paleocene
18. The epoch that we currently live in is called the (1)______ and it began (2)_____ years ago:
A. (1) Quaternary
(2) 1000
B. (1) Pleistocene
(2) 100,000
C. (1) Tertiary
(2) 1 million
D. (1) Holocene
(2) 10,000
E. (1) Cenozoic
(2) 10 million
18. About 66 million years ago…
A. a giant meteorite collided with the Earth
B. all the dinosaurs went extinct
C. the Tertiary Period began
D. the Paleocene Epoch began
E. all of the above
18. If a certain species is known, based on fossil evidence, to have existed on Earth from the Permian to the
Cretaceous Periods, in which of the following aged rocks would we never find fossils of this creature?
A. Permian
B. Cretaceous
C. Jurassic
D. Devonian
E. Triassic
18. A sedimentary bed contains three fossils: A, B, and C. Fossil A is known to have existed in the Cambrian and
Ordovician Periods only. Fossil B existed in the Ordovician and Silurian Periods only. Fossil C existed for a very long
time on Earth- during the Cambrian, Ordovician, Silurian, Devonian, and Carboniferous Periods. Based on this fossil
assemblage, what must the age of the rock be?
A. Cambrian
B. Ordovician
C. Silurian
D. sometime between the Cambrian and the Carboniferous is all that we can tell
E. it’s impossible to tell
18. Which of the following statements about radioactivity is false?
A. radioactivity involves the release of subatomic particles from an atom’s nucleus
B. the radioactive decay process is not affected by the nature of its environment
C. alpha decay and beta decay are two possible types of radioactive decay
D. all isotopes of an element have the potential to undergo radioactive decay
E. radioactive decay produces gamma rays and heat during the decay process
18. Which of the following statements is true of alpha decay when referring to radioactivity?
A. an atom releases a pair of protons and a pair of neutrons from the nucleus
B. an atom releases a proton and a neutron from the nucleus
C. an atom releases an electron from the nucleus causing a neutron to turn into a proton
D. an atom absorbs an electron into the nucleus causing the atomic number to decrease by 1
E. an atom remains unchanged but gives off gamma rays and generates a lot of heat
18. Which of the following statements is true of beta decay?
A. an atom releases a pair of protons and a pair of neutrons from the nucleus
B. an atom releases a proton and a neutron from the nucleus
C. an atom releases an electron from the nucleus causing a neutron to turn into a proton
D. an atom absorbs an electron into the nucleus causing the atomic number to decrease by 1
E. an atom remains unchanged but gives off gamma rays and generates a lot of heat
18. An isotope that undergoes decay starts off as a/an (1) _____ and becomes a (2) _____:
A. (1) unstable isotope
(2) stable isotope
B. (1) daughter
(2) son
C. (1) daughter
(2) parent
D. (1) parent
(2) daughter
E. (1) parent
(2) mutant
18. Which of the following statements about radioactive decay is TRUE?:
A. the rate of decay of an isotope never changes
B. alpha decay is always followed by beta decay
C. the amount of daughter isotopes is always decreasing
D. all available atoms of an unstable isotope will fully decay after two half-lives
E. all daughter isotopes are stable isotopes
18. Which of the following statements about radioactive decay is TRUE?:
A. decay rates are affected by the physical and chemical environment
B. alpha decay is always followed by beta decay
C. the amount of daughter isotopes is always decreasing
D. one half of the available unstable isotopes always decays during one half-life
E. all daughter isotopes are stable
18. The correct definition of half-life when referring to an unstable isotope is as follows:
A. the amount of time needed to completely decay all parent isotopes into daughter isotopes
B. half the amount of time needed to completely decay all parent isotopes into daughter isotopes
C. the amount of time needed to completely decay all daughter isotopes into parent isotopes
D. the amount of time needed to decay half of the daughter isotopes into parent isotopes
E. the amount of time needed to decay half of the parent isotopes into daughter isotopes
18. If the half-life of a radioactive isotope is 1 million years, and a crystal forms containing 100 of these isotopes,
how old is the crystal at the point when only 25 of the original radioactive isotopes are left in the crystal?
A. 1 million years old
B. 2 million years old
C. 3 million years old
D. 4 million years old
E. 5 million years old
18. If the half-life of an isotope is 1 million years, and 200 of these isotope atoms get trapped in a crystal in an
igneous rock when it first forms, how old will the rock be when there are only 25 of these isotopes left in the
crystal?
A. 1 million years old
B. 2 million years old
C. 3 million years old
D. 4 million years old
E. 5 million years old
18. Radioactive decay rates can be used to determine the absolute age of a rock because we can measure the
amount of decayed isotopes in the rock to see how much time has passed since the decay process first began.
BUT…
A. we cannot figure out the age of the earth because radioactivity didn’t always occur
B. it’s impossible to estimate the rates of decay of most isotopes
C. we can’t figure out the age of deposition of sedimentary rocks
D. we always have to be careful about the decay rate changing over time
E. igneous rocks can’t be dated because isotopes decay faster in magma than inside a crystal
18. How old have moon rocks been determined to be, based on radiometric dating?
A. 4.6 billion years old
B. 4.5 billion years old
C. 4.1 billion years old
D. 4 billion years old
E. 2 billion years old