Download The Rock and Fossil Record

The Rock and Fossil Record
Objectives
• Explain how geologic time is recorded in
rock layers.
• Identify important dates on the geologic
time scale.
• Explain how environmental changes
resulted in the extinction of some species.
Geologic Time
• The Rock Record and Geologic
Time One of the best places in
North America to see the Earth’s
history recorded in rock layers is
in Grand Canyon National Park.
These layers represent almost
half, or nearly 2 billion years, of
Earth’s history.
•
The Fossil Record and
Geologic Time Fossils of plants
and animals are common in some
rocks. These fossils contribute to
our understanding of geologic
time.
I. The Geologic Time Scale
A. Divisions of Time Geologists have divided Earth’s
history into sections of time. The largest divisions of
geologic time are eons. Eons are divided into eras, eras
into periods, and periods into epochs.
•
The Appearance and Disappearance of Species At
certain times during Earth’s history, the number of
species has increased or decreased dramatically. An
increase or decrease in the number of species often
comes as a result of either a relatively sudden increase
or decrease in competition among species.
The Geologic Time Scale
B. The Paleozoic Era—Old Life The Paleozoic era lasted
from about 543 million to 248 million years ago. It is the
first era well represented by fossils. Ended with the
largest mass extinction in Earth’s history.
C. The Mesozoic Era—The Age of Reptiles The
Mesozoic era began about 248 million years ago. The
Mesozoic is known as the Age of Reptiles because
reptiles, such as dinosaurs, inhabited the land.
D. The Cenozoic Era—The Age of Mammals The
Cenozoic era began about 65 million years ago and
continues to the present.
Science Journal Entry #2
• Draw the geologic
time scale.
• Draw and give
examples of
animals alive during
the Paleozoic,
Mesozoic, and
Cenozoic Eras.