Index fossils are used to date rock strata that would otherwise be very difficult to date. Which of these statements describes a key characteristic of index fossils?
A. They are similar to other fossils.
B. They existed in a unique location.
C. They existed for a short span of time.
D. They are present in very small numbers.
C
100
Jacob has one older brother and one younger sister. He wants to explain relative dating to them using their ages as an example. Which of the following arrangements would show the concept of relative dating?
A. forming a line in the order of age
B. forming a line in the order of height
C. forming a line in the order of weight
D. forming a line in the order of birth month
A
100
true/False: Shells and bones are trace fossils
false
200
What is geology?
It is the scientific study of the history of Earth and the processes that shape it.
200
True or False: Eras are longer than Periods
true
200
How does sedimentary rock usually form?
A. in large crystals
B. in vertical layers
C. in swirling bands
D. in horizontal layers
D
200
True or False: In order to use isotopes to date rocks, the isotopes must decay at a set rate
True
300
What is catastrophism?
Geologic changes only occur in sudden, devastating events.
300
What is the main criterion that scientists use to decide where to place the boundaries between the major divisions of the geologic time scale?
major changes that are recorded in the fossil record
300
How does the law of crosscutting relationships explain the age of a fault caused by an earthquake?
The fault is younger than the rocks it cuts through.
300
Earth’s surface features slowly change over time. For example, sharp, jagged mountain ranges become lower and more rounded over time. What is responsible for this change in their shape?
weathering and erosion
400
Early in the Paleozoic Era, plants began to colonize the continents. Which of the following changes to Earth's surface most likely happened as a result?
rates of erosion decreased
400
In which epoch do we currently live?
Holocene
400
What is the law of superposition?
A sedimentary rock layer in its original position is older than the layers above it and younger than the layers below it.
400
Trace fossils are much more common than body fossils. Why?
A single animal can leave thousands of traces in its lifetime but will leave only one body when it dies.
500
What was the first organism that released oxygen into Earth’s atmosphere, changing its composition?
cyanobacteria
500
According to the fossil record, when did the dinosaurs become extinct?
at the end of the Mesozoic Era
500
How do scientists use fossils to determine the relative ages of rock layers?
by comparing fossils in many different rock layers
500
List the four major divisions of Earth's history that are based on major events in Earth's geological history.