Transcript Section 8.1 Relative Age2006

Chapter 8
Section 1
Determining Relative Age
Chapter 8
e Age
Objectives
State the principle of uniformitarianism.
Explain how the law of superposition can be
used to determine the relative age of rocks.
Compare three types of unconformities.
Apply the law of crosscutting relationships to
determine the relative age of rocks.
How old is the Earth?
It was first believed to be only
6,000 years old.
Principle of Uniformitarianism
• It is the theory that geologic processes at
work in the present were also at work in
the past. James Hutton
– Based of observable physical evidence
• Weathering
• Erosion
• Deposition
• Volcanism
Relative Age
• The age of an object or event
compared with the ages of other
objects or events.
List these events in the order
they happened.
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Iraq war
Persian Gulf War
WW II
Civil War
Revolutionary War
WW I
Vietnam War
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Iraq War
Persian Gulf War
Vietnam War
WW I
WW II
Civil War
Revolutionary War
• An undeformed sedimentary rock
layer is older than the layers
above it and younger than the
layers below it.
Which is the oldest?
How do we determine the original
arrangement of the layers?
• Shape of the
bedding planes
Particle size
Ripple
marks
Determining Relative Age
Unconformity
• A boundary between rocks that indicates a
gap in the rock record
• Usually results from the erosion of some
rocks
Nonconformity
• An unconformity in which stratified
rock rests on unstratified rock
Angular Unconformity
• A boundary between
horizontal and tilted
layers of rock
Number Oldest to Youngest
Disconformity
• A boundary between layers of rock that
have not been deposited continuously
• An intrusion or a fault is always younger
than the rock layers it cuts through
Number Oldest to Youngest
Number Oldest to Youngest
Number Oldest to Youngest
Assignments
• Direct Reading Work Sheet
• Key terms
• Relative age Activity