Transcript dating_rock_layers

Dating Rock Layers
How to tell how old the layers of
rock are.
What is Age?
Relative Age – The age compared to the ages
of other rocks. (older than this rock, younger
than that rock.)
Absolute Age – The number of years since the
rock formed. (150 million years old, 10
thousand years old.)
What are the ways to tell
RELATIVE AGE.
What is the Law of Superposition?
In horizontal sedimentary rock layers, the
oldest layer is at the bottom.
Each higher layer is younger than the layers
below it.
Extrusion vs Intrusion
EXTRUSION
INTRUSION
• When magma cools on
the surface of the Earth
it’s called an
EXTRUSION.
• When magma cools
beneath the surface of
the Earth it’s called an
INTRUSION.
• Extrusions are always
YOUNGER than the rock
it is sitting on.
• Intrusions are always
YOUNGER than the
rocks around it.
Extrusions? Intrusions?
G
First of all, What
whichisrock
this layer
called?
is the oldest?
F
EXTRUSION
E
D
More rock layers are deposited on
top of the extrusion.
INTRUSION
C
B
A
Your Turn To Label
In your notes, draw a similar structure and label the following:
Intrusion
Extrusion
Youngest
Oldest
What is a Fault?
• A BREAK in the
Earth’s crust.
• A fault is always
YOUNGER than the
rock it cuts through.
This crack in the
rock layers is called
a fault.
What is an Unconformity?
• The surface where new rock layers meet a
much older rock surface beneath them.
• An unconformity shows where some rock
layers have been lost because of erosion.
Become a Geologist
• Put the layers in order from oldest to
youngest for the picture below:
Become a Geologist
• Put the layers in order from oldest to
youngest for the picture below: