Relative Age of Rocks

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Transcript Relative Age of Rocks

RELATIVE AGE OF ROCKS
Lesson 10-2
Absolute or Relative?
•Anthony is the youngest.
•Melony is 4 years old.
•Michael is older then
Sasha.
•Sasha is 16 years old.
•Ashley is older than
Melony, but younger than
Sasha.
Relative Dating
•Used to determine the order of
events and the relative age of
rocks by looking at the position
of rocks in a sequence
•Numbers are not used
•Ex: “I am older than you.”
Law of Superpostion
•In an undisturbed layer
of rock, the oldest rocks
are on the bottom and
the younger rocks are
toward the top
Original Horizontality
•Layers of rock are
initially deposited in
flat, horizontal layers
Folding
Inclusion
•Older rock included in the
formation of newer rock
Cross-cutting
•Intrusions
•igneous dikes ↑ and sills→
•Faults
•When one geologic feature
(younger) cuts across another
geologic feature (older)
Unconformity
•When erosion removes
existing rock layers and
causes a gap in the
geological record
Index Fossils
ID ages of different rocks