SEPT.10, 2011 LEQ 4 LAW OF SUPERPOSITION
Homework Due tomorrow!Words to know: relative age, absolute age, law of superposition, index fossil, intrusionDo 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
age2. Understand and apply the law of
superposition to diagrams and descriptions3. 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 ageabsolute 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-ChartRelative Age Absolute Age-Tells age compared to something else-Uses words like “older,” “younger,” and “same age as”-Ex: I am younger than my brother.
-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 ItIn undisturbed sedimentary rock layers, -Oldest rock layers are at the bottom-Youngest rock layers are at the top
Draw it
Example
The Grand Canyon
Sentence
The Law of Superposition tells us
the relative age of rocks.
Law of Superposition
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 ageas the layer of rock it is in
If there is a fossil in a rock layer, and weknow 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!
70s80s
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 itb. Neither older nor younger than other layersc. Older than the layer above it and younger
than the layer below itd. Always older than any vertical layers
