Changes through

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Changes through Geologic Time Reading the Rocks
Learning Objectives
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Our World Define change?
Change is a relative term! Defining change
requires a comparison to a previous or standard
condition. What previous/standard condition
should we use?
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Change - Requires Time
Different Perspectives about Geologic Time
Geoscience Perspective 4.6 billion years
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Key Concept Change Occurs Because of the
Exchange of Matter and Energy
Input ? ?
Output cause
effect Energy/Matter

Energy/Matter
System Parts and Properties
At Equilibrium Input Output At Dynamic
Equilibrium Changes in Input - Changes in
Output 0 Modify Input or Output Change in
System Change in Input - Change in Output
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Change Connects the Spheres An Earth Systems
Approach
Everything is Connected to Everything Else!
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Rock Cycleand Plate Tectonics
Every Rock Tells a Story Past, Present, and
Future
From http//www.utexas.edu/ tmm/npl/mineralogy/Mi
neral_Genesis/
Please View Interactive Rock Cycle Animation
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United States Geologic Map (3-D view above
ground (x - y time (i.e., age))
http//tapestry.usgs.gov/two/color.html
Rocks of Ages An explanation of the legend
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Geologic Cross Section (x and z)
Y (in and out of page)
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Activity Your State, Your Rocks, Your History

• Part I. Explore your State

http//www.paleoportal.org/index.php?globalnavtim
e_space
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Geologic Time Scale
More Details On Time Scale Here
Hadean
http//paleobiology.si.edu/geotime/main/
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Geologic Time Scale Product of Reading the
Rocks

• Relative Age-Dating Techniques
• Principles of Stratigraphy

? Nicolas Stenos Laws (1638-1686) - Original
Horizontality - Superposition - Principle
of Lateral Continuity
? James Hutton (1726-1797) - Unconformity
- Law of Cross Cutting Relationships - Law
of Inclusions
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Geologic Time Scale Product of Reading the
Rocks

• Relative Age-Dating Techniques
• Principles of Stratigraphy

Laterally Continuous
? Nicolas Stenos Laws (1638-1686) - Original
Horizontality - Superposition - Principle
of Lateral Continuity
Younger
Laterally Continuous
Older
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Geologic Time Scale Product of Reading the
Rocks

• Relative Age-Dating Techniques
• Principles of Stratigraphy

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Intrusion
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? James Hutton (1726-1797) - Unconformity
- Law of Cross Cutting Relationships - Law
of Inclusions
Fault
2
1
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Geologic Time Scale Product of Reading the
Rocks

• Relative Age-Dating Techniques
• Principles of Stratigraphy

? Great Unconformity
Paleozoic
Great Unconformity
Precambrian
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Geologic Time Scale Product of Reading the
Rocks
What Happened First?

• Relative Age-Dating Techniques
• Principles of Stratigraphy

Deposit A (oldest) Intrude B C (erosion/ Unconform
ity) Deposit D
Deposit A Intrude B Intrude C
Deposit A Deposit B Deposit C Faulting along D
Deposit A Deposit B Deposit C Faulting D F
(erosion) Deposit A
F
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Geologic Time Scale Product of Reading the
Rocks
Activity Now its your Turn! Post your sequence of
events to the Discussion Board Event Sequencing

• Relative Age-Dating Techniques
• Principles of Stratigraphy

E
D
E
A
F
B
C
C
H
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Activity
The Earth Has A History Video

• Record Five Key Concepts from the video.
• Post your five key concepts to the Discussion
  Board entitled, Earth History Video.
• Comment on at least two other entries.

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The Earth Has A History Video
Key Concept Uniformitarianism
? The physical and biologic features of the
Earth (both past and present) were produced by
the same processes acting today. ? Physical and
chemical laws that govern the geologic processes
have always been the same. ? Processes similar,
rates may be different. e.g. Impact cratering
James Hutton (1726-1797)
The present is the key to the past We use
modern environments to understand ancient ones.
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Geologic Time Scale Product of Reading the
Rocks

• Relative Age-Dating Techniques
• Principles of Stratigraphy

2.Absolute Age-Dating Techniques
Radiometric Dating
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Geologic Time Scale Product of Reading the
Rocks
1. Relative Age-Dating Techniques
Principles of Stratigraphy
What came first?
Deposit P (oldest) Deposit K Deposit M Deposit
S Intrude R Erosion at
A. (Unconformity) Deposit B Lava Flow J
Deposit F (youngest)
Lava Flow
15 MYA
_at_ 100 MYA
_at_ 15 MYA
Granite Intrusion
100 MYA
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2. Absolute Age Dating Techniques
Parent Daughter ½
Life Uranium 238 Lead 206 4.47 billion
years
Quantify the age of a rock in years using
radiometric dating
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2. Absolute Age Dating Techniques
Parent Daughter ½
Life Carbon 14 Nitrogen 14 5730 years
For a Visual Real-Time Illustration of
Half-Life Click Here
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2. Absolute Age Dating Techniques
Examples of Radioactive Elements
Parent Daughter ½
Life Potassium 40 Argon 40 1.25
billion yrs Rubidium 87 Strontium 87
48.8 billion yrs Thorium 232 Lead 208
14 billion years Uranium 238 Lead 206 4.47
billion years Carbon 14 Nitrogen 14 5730 years
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Return to Activity Your State, Your Rocks, Your
History

• Part II. Explore your State and its Rocks

http//www.paleoportal.org/index.php?globalnavtim
e_space