Transcript Law of Superpositionx

Homework Due tomorrow!
Words to know: relative age, absolute age, law
of superposition, index fossil, intrusion
Do now:
1. Do you have brothers/sisters?
2. If so, how old are they? Are they older or
younger than you?
3. If not, how old is your closest friend? Are
they older or younger than you?
LEQ #4: What information do humans get from
rock layers, index fossils, and ice cores in
order to paint a picture of Earth’s History?
By the end of today, SWBAT…
1. Compare and contrast absolute and relative
age
2. Understand and apply the law of
superposition to diagrams and descriptions
3. Explain how index fossils are used to date
rocks
Activating Strategy

Put the following events in order:
 Nuclear Bomb dropped on Hiroshima, Japan (1945)
 George Bush became President (2000)
 Pluto was no longer considered a plant (2006)
 The Internet was “invented” (1994)
 The U.S. launched the first space shuttle (1981)

How did you decide to put them in order?
Look back at your words to know…
relative age
absolute age
What does relative mean? Think about
how things relate
 What does absolute mean? Think about
math
 What do you think these words mean
when describing age?

T-Chart
Relative Age
-Tells age
compared to
something else
-Uses words like
“older,” “younger,”
and “same age as”
-Ex: I am younger
than my brother.
Absolute Age
-Tells the exact age
-Uses numbers
-Ex: My brother is
16.
Pair and Write!
With your partner:
 1.) Tell each other your absolute age
 2.) Write a sentence about how old YOU
are RELATIVE to your partner
 3.) Discuss  What is the difference
between absolute and relative age?

Scientists use rocks to figure out
Earth’s History!
We can see 2 BILLION years worth of Earth's
geologic history in the Grand Canyon!
You just figured out
the…
Law of
Superposition!!!
Define It
Draw it
In undisturbed
sedimentary rock layers,
-Oldest rock layers are at
the bottom
-Youngest rock layers are
at the top
Example
Law of Superposition
The Grand Canyon
Sentence
The Law of
Superposition tells us
the relative age of
rocks.
So what is THIS???
INTRUSION!!!
Magma that pushes through rock layers. Is
younger than the layers it cuts across because
the layers had to be there before it could cut
across them!.
 Science says… intrusion!

Hot Question!

If you found this fossil in your backyard,
what could you infer about how your
backyard looked in the past?
Absolute Dating Techniques
Index Fossils: fossils of a
species that only existed
during a limited time
 The fossil is the same age
as the layer of rock it is in
 If there is a
fossil in a rock layer, and we
know what time period the
animal lived, we can conclude
that the rock was formed
during that period.

Index fossils help scientists figure
out how old rock layers are!
70s
80s
How to find the absolute age
of an index fossil…
Radioactive dating… more to come on
this, but take a look at this chart…
 Think.Pair.Share.

Use the diagrams on your
desk. With your partner,
answer the question on your
dry erase board. When I say
“3-2-1, Boards Up,” you
should hold your board in the
air. If your board does not go
up immediately, you will be
DQ’ed for that question.
Real Life Practice  Look at the
cup on Ms. K’s desk

What is the oldest rock layer? How do
you know?
Real Life Practice  Look at
the cup on Ms. K’s desk

What is the youngest rock layer? How
do you know?
Real Life Practice  Look at
the cup on Ms. K’s desk

Imagine that there is a layer of magma
pushing up through all 4 “rock” layers.
What is this called?
Real Life Practice  Look at
the cup on Ms. K’s desk

List all rock layers in order from oldest
to youngest.
Real Life Practice  Look at
the cup on Ms. K’s desk

What is the name of the law that tells us
this is true?
Hot Question

The law of superposition states that in
horizontal layers of sedimentary rock, each
rock layer is ___________.
 a. Younger than the layer above it and older
than the layer below it
 b. Neither older nor younger than other layers
 c. Older than the layer above it and younger
than the layer below it
 d. Always older than any vertical layers