Relative Dating

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Relative Dating
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DO NOW MONDAY

• What is an index fossil?
• What is it used for?

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Learning Targets-MONDAY

• Explain relative dating using index fossils.
• Identify the sequence of rock layers using the
  Law of Superposition.

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Law of Superposition

• Younger rock layers are above older ones of the
  rock layers have not been disturbed.
• But what if they have been disturbed?

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Principle of Inclusion

• When pieces of rock/fossils, etc. are included in
  a layer of rock, then the pieces are older than
  the layer of rock.
• The pieces had to exist before they could be
  included in the layer of rock.

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Cross-Cutting Principle

• If many layers of rock are cut by a fault, then
  the fault line must be younger than the layer of
  rock.
• The layer of rock had to have been there first in
  order to have been cut by the fault line.

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DO NOW TUESDAY
Which letter is pointing to the oldest
layer? Which law of relative dating explains how
we know?
C.
B.
A.
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Learning Targets- TUESDAY

• Explain relative dating using index fossils.
• Identify the sequence of rock layers using the
  Law of Superposition.

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Snickers Relative Dating Activity

• 1. Draw a cross-section of your snickers bar on
  your sheet. As you draw, be thinking about which
  layer formed first, second, and so on.
• 2. Label (on your drawing) the four main layers
  of your snickers bar.
• 3. Answer questions 2-4 on your sheet.
• 4. Cut a fault into your snickers bar.
• 5. Redraw a cross section of your snickers bar.
• 6. Answer question 5 on your sheet.
• 7. Do number 6 on your sheet.

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Relative Dating
There are 3 Rules that allow scientists to
date rocks

• 3 Laws of Relative Dating
• Superposition Layer on top Is always youngest

1.
LEARNING CHECK 1 Which layer on your snickers
bar is the youngest and which is the oldest
2. Cross-Cutting Principle Any fault or magma
plume that cuts across a rock is always younger
than the rock it cuts across
2.
LEARNING CHECK 2 Is the fault you cut into the
snickers older or younger than the snickers rock
around it?
Fault
3.
3. Inclusions Pieces of rocks that are included
in a rock layer are OLDER than the the rock
layer.
LEARNING CHECK 3 What are the inclusions in your
snickers bar? Are they older or younger than the
caramel layer itself?
Inclusions
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EXIT SLIP TUESDAY
Give the sequence of the numbers in the diagram
below from youngest (on top) to oldest (on
bottom.)