1. Views of Earth’s Past 5.1 Rocks provide a timeline for Earth. 5.2
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Views of Earth’s Past
the BIG idea
Rocks, fossils, and other types of natural evidence tell Earth’s story.
5.1
Rocks provide a timeline for Earth.
5.2
The geologic time scale shows Earth’s past.
5.3
Earth’s past is revealed in rocks and fossils.
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2. Rocks provide a timeline for Earth.
5.1
Rocks provide a timeline for Earth.
CALIFORNIA
Content Standards
7.4.c Students know that the rock cycle includes the formation of new sediment and rocks that are often found in layers, with the oldest generally on the bottom.
7.4.d Students know that evidence from geologic layers and radioactive dating indicates Earth is approximately 4.6 billion years old and that life on this planet has existed for more than 3 billion years.
relative age
rock cycle
index fossil
absolute age
half-life
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3. Rocks provide a timeline for Earth.
5.1
Rocks provide a timeline for Earth.
Sedimentary rock layers show the order in which rocks formed. The order of the layers is used to determine the relative ages of fossils found in the rock.
relative age
rock cycle
index fossil
absolute age
half-life
Radioactive dating can be used to determine the absolute age of igneous rock.
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Scientists combine information about the relative and absolute ages of rocks and fossils to construct a timeline of Earth.
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OUTLINE

4. Rocks provide a timeline for Earth.
5.1
Rocks provide a timeline for Earth.
Scientists combine information about the relative and absolute ages of rocks and fossils to construct a timeline of Earth.
relative age
rock cycle
index fossil
absolute age
VISUALIZATION
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Watch molten rock cut through layers of sedimentary rock.
half-life
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5. The geologic time scale shows Earth’s past.
5.2
The geologic time scale shows Earth’s past.
CALIFORNIA
Content Standards
7.4.a Students know Earth processes today are similar to those that occurred in the past and slow geologic processes have large cumulative effects over long periods of time.
7.4.b Students know the history of life on Earth has been disrupted by major catastrophic events, such as major volcanic eruptions or the impacts of asteroids.
uniformitarianism
geologic time scale
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6. The geologic time scale shows Earth’s past.
5.2
The geologic time scale shows Earth’s past.
The geologic time scale divides Earth’s history into eons, eras, periods, and epochs.
The divisions are based on major changes or events that occurred in Earth’s history.
uniformitarianism
geologic time scale
EON
EPOCH
ERA
PERIOD
today
*bya = billion years ago †mya = million years ago
Phanerozoic eon
Cenozoic era
Mesozoic era
Paleozoic era
Proterozoic eon
Archean eon
Hadean eon
Precambrian time
500 mya†
4.6 bya*
3 bya
2 bya
1 bya
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7. 5.3 CALIFORNIA Content Standards
Earth’s past is revealed in rocks and fossils.
CALIFORNIA
Content Standards
7.3.c Students know how independent lines of evidence from geology, fossils, and comparative anatomy provide the basis for the theory of evolution.
7.4.b Students know the history of life on earth has been disrupted by major catastrophic events, such as major volcanic eruptions or the impacts of asteroids.
7.4.e Students know fossils provide evidence of how life and environmental conditions have changed.
original remains
ice core
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8. 5.3 Earth’s past is revealed in rocks and fossils.
Fossils are traces or remnants of past life. Many fossils are found in rock. Rocks, fossils, and other natural evidence provide
information about
how Earth and life
on Earth have
changed over time.
original remains
ice core
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VISUALIZATION
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Explore how fossils form.
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9. Rocks provide a timeline for Earth.
5.1
Rocks provide a timeline for Earth.
I. Rocks provide a timeline for Earth.
relative age
A. Changes in rocks provide a record of the past.
rock cycle
B. The three main types of rocks form in different ways.
index fossil
absolute age
C. Layers of sedimentary rock show relative age.
half-life
1. Igneous Rock and Sedimentary Layers
2. Index Fossils
D. Radioactive dating can show absolute age.
1. Half-Life
CHAPTER
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2. Using Absolute and Relative Age
KEY CONCEPT
SUMMARY

10. The geologic time scale shows Earth’s past.
5.2
The geologic time scale shows Earth’s past.
II. The geologic time scale shows Earth’s past.
uniformitarianism
A. Earth is constantly changing.
geologic time scale
B. Small, gradual changes become large changes over time.
C. The geologic time scale divides Earth’s history.
1. Divisions of Geologic Time
2. Phanerozoic Eon
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KEY CONCEPT
SUMMARY

11. Earth’s past is revealed in rocks and fossils.
5.3
Earth’s past is revealed in rocks and fossils.
III. Earth’s past is revealed in rocks and fossils.
original remains
A. Fossils, and original remains give clues about the past.
ice core
1. Types of Fossils
2. Fossil Formation
3. Fossils in Rocks
4. Original Remains
B. Fossils and other natural evidence show changes in life and the environment.
1. Ice Cores
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2. Tree Rings
3. Finding the Age of Fossils
KEY CONCEPT
SUMMARY

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