Chapter 4
Who came up with the concept that geologic processes operating at present are the same processes that operated in the past?
James Hutton
In which of the following time periods were dinosaurs the dominant creatures?
Mesozoic
How does an angular unconformity form?
Older rocks are tilted, eroded, and overlain by younger rocks.
Which of the following is the earliest (oldest) chapter of geologic time?
Precambrian
How would we use isotopic ages to infer the ages of the upper and lower unit in this diagram?
The dike is younger than the lower unit but older than the upper unit.
This photograph shows light-colored granite and darker diorite (both igneous rocks). Which of the following statements is true?
The granite is younger because it crosscuts the diorite.
Upon what basis were the upper and lower boundaries of the Mesozoic Era defined?
abrupt changes in the types of fossils, representing mass extinctions
The geologic timescale details and divides geologic time based upon
fossil data.
This figure shows the main subdivisions of the geologic timescale. Which of these is the Cenozoic?
geologic time A
What type of feature is shown in this photograph of Siccar Point, Scotland?
unconformity
Of the following numbered units, which is the youngest?
unit 9 The top
The oldest known rock found on Earth is dated at
over 4 billion years old.
What type of feature is represented by the boundary between geologic units 2 and 3?
unconformity
What would fossil ages from the geologic timescale tell us about the age of this unconformity?
All of these choices are correct.
Which of the four numbered features on this figure is the oldest?
1
Which numbered layer in this photograph represents the oldest layer?
1 the hillside
Which sequence of numbers reflects the order in which the layers were deposited?
1, 2, 3, 4
If a rock started with 1,000 atoms of a parent but now contains 250 atoms, how many half lives have passed?
2 half lives
Which of the four numbered features on this figure is the youngest?
4 surface
What factors are the most critical in determining whether a fossil is preserved?
Whether the creature had hard parts and how fast it was buried.
Which principle can be used to determine the relative age of an igneous intrusion called a dike?
cross-cutting relations
Which principle of relative age dating can be used to determine when the river formed on the landscape?
cross-cutting relations
What is the youngest event represented in this block diagram?
erosion of a canyon by a river
The term half life represents the time it takes
for half of the parent atoms to decay into daughter atoms.
The fossil ferns in this photograph probably indicate that the rock was deposited
on land.
Which principle is used to determine the age of rocks by ordering them from oldest on the bottom to the youngest on the top?
superposition
Using the data in this table, calculate the number of half-lives that have passed for the dike (unit D on this table).
table of isotopic measurements 1
The geologic relationships in this figure indicate
that the lava flow is younger than the landscape surface partially covered by the lava flow.
Early Earth would have been inhospitable to many life forms of today because
the atmosphere lacked oxygen.
Of the following numbered units, which is the oldest?
the granite 4
Missing geologic time caused by erosion is called a(n):
unconformity
How did an oxygen-rich atmosphere develop from a carbon dioxide-rich atmosphere?
through photosynthesis by cyanobacteria