Study Guide Flashcards
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 rock
and fossil record
Which is not an accurate statement about the
geological time scale?
The geological time scale is unchanging.
What proportion of the geological time scale
is classified as Precambrian time?
over 80%
Which example shows that not all geological
change occurs slowly?
meteorite impact
Which statement is not accurate regarding
the changes in Earth’s surface over time?
Now that the Earth has been shaped by
geological processes, it will not be
reshaped.
In the rock layers of a prairie environment, a
fossil of an extinct species of shark is found.
Many layers below also contain water-
dwelling organisms, but no fossils of sharks
or other aquatic animals are found in the
layers above the rock layer where the shark
fossil was found. Which statement is not a
conclusion that can be made from the
discovery of the shark fossil?
The relative age of the shark fossils cannot
be determined since the shark fossils do not
appear in all of the rock layers.
A layer of volcanic ash is found between two other rock layers. Absolute dating shows that the ash is
about 65 million years old. Which conclusion can be made from these three rock layers?
The top layer is less than 65 million years old.
Geologists were exploring rock layers in an area. In one layer, they found igneous rock that was about
95 million years old. In the layers below the igneous layer, they found dinosaur fossils. In the layer
above the igneous layer, no dinosaur fossils could be found. Provide an explanation as to what might
have happened in this area.
There’s the Earth’s core and the surface. The core is extremely warm. Igneous rock is commonly found in volcanoes and their eruptions. Extinction is what caused the volcanic eruption.
The geological time scale is organized into four major divisions. List these divisions and describe how
they are determined.
Eons, eras, periods, epochs are all divisions of the geological time scale. They all have lasted for millions of years.
A geologist collects fossils from a hill that is made up of many layers of rock. The fossils include a tree
leaf that is 130 million years old and an ocean-dwelling animal called a trilobite that is 400 million years
old. Identify a conclusion the geologist can make about the area where the fossils were found, and
explain why.
The tree leaf is 130 million years old. 400 million years ago, the trilobite, an aquatic animal, existed in what’s now land. The environment most likely changed. From an ocean dwelling environment to a land dwelling environment. This is because the environment got dry, also known as an environmental change.
What is a fossil?
A fossil is any preserved remains from a geologic time scale such as bones, skeletons, etc.
Diagram’s time periods:
Precambrian Era - 12:00am-10:00pm
Paleozoic Era - 10:00pm-11:40pm
Mesozoic Era - 11:40pm-11:55pm
Cenozoic Era - 11:55pm-12:00am
- What does this diagram tell you about these different time periods?
- What are some statements that describe the geologic time scale?
- the order in which they occurred, the length of time they lasted in relation to each other
- It is divided based on evidence in the fossil record.
Some events are arranged according to relative dates.
It is divided based on evidence in the rock record.
White rock layer- Top one
Red rock layer- Middle one
Brown rock layer- Bottom one
- The rock layers in the photo were laid down horizontally (<—->) and are undisturbed. Therefore, you can conclude that the white layer is ____ than the red layer, and that the thick brown layer is the ____ of the layers shown here.
- An extremely thin layer of volcanic ash is found between the white layer on top and the thin red layer in the middle. Absolute dating showed that the ash is about 43 million years old. What can you conclude based on this information?
- younger, oldest
- The top layer is younger than 43 million years old.
The bottom layer is older than 43 million years old.
Scientists study current geologic processes to learn about past processes such as tectonic plate motion, weathering, erosion, and deposition.
How is it possible to look at geologic processes that shape Earth today to learn about the past?
Studying volcanic activity can give us insight by seeing how islands are currently expanding or shrinking due to tectonic plate activity.
Scientists use the rock record and the fossil record as events for events and conditions.
What can you infer from the rock record and the fossil record? Give two specific examples of evidence and how the evidence helps scientists organize geologic time.
An ash layer’s absolute age can help scientists find the relative ages of rocks and fossils above and below the ash layer. Disappearance of organisms in the fossil record is evidence of an extinction.
