Transcript Unit 3 Earth History Day 4 2016

Unit 3 Earth History: Day 4
Warm-up –
Focus: Absolute Age of Rocks
1. Put your 3 flash cards in
12/8/16
the box.
2. Analyze the diagram to the
right.
a. On page 4 in your notebook,
put the layers and events in
order from oldest to
youngest. Don’t forget to
include the igneous intrusion
and the lava flow.
b.Is it possible to infer the
approximate ages of rock
layers 1,2 and 3? If so,
how? How about Layer 4?
Plan for the Day
1. Continue the “Geologic Column”
activity
2. Begin learning about Absolute
Age-Dating of Rock
*Notes
*Activities
3. Wrap-up
Homework
1. Make a flash card for #11
“Half-Life”.
2. Worksheet “Radioactive Dating of
Rocks” and “A Continuous Process”
due Friday.
Essential Question –
How can elements in rocks
help us know the exact age
of those rocks?
Please take out the
“Analyzing the Geologic
Column” activity and let’s
continue. This should take
10-15 minutes.
Analyze: A. Is there a place on Earth
that has all the layers of the geologic
column? Explain your answer.
B. If a trilobite fossil that is 400 million
years old is found in a layer of rock, how
can scientists determine the actual age of
the rock layer?
Evaluate: Sharks have existed for millions
and millions of years. Would a shark’s
tooth be a good index fossil? Explain your
answer.
Can you figure out the correct chronological
order of these rock layers and events from
oldest to youngest?
Write a brief geologic history of this rock outcrop
based on the positions of the layers and the events
affecting the layers.
Let’s learn about how
scientists determine the
exact age of rocks and
fossils.
Get your new vocab. sheet
ready.
Vocabulary
 9.Absolute Age-Dating of Rock -any
method of measuring the age of an event or
object in years.
A.D. 1- The exact age (not just older or younger)
Vocabulary
 10.Radioactive Decay: When the atoms of
one element break down to form atoms of
another element.
 A.D. 1 -These elements are radioactive and
unstable
 A.D. 2 -They release particles and energy
as they break down (decay) into more
stable elements (add the blue part)
 A.D. 3 -Occurs naturally in igneous rock
Vocabulary
 11.Half-life: The rate of decay of
radioactive elements…the amount of time it
takes for 1/2 of the radioactive (unstable)
element in an igneous rock to decay
(change) into a stable (non-radioactive)
element.
 A.D. 1 -As the radioactive (unstablePARENT) element decreases, the nonradioactive (stable- DAUGHTER) element
increases
 A.D 2- This rate is constant & never
changes.
Vocabulary Continued
12.Radiometric dating : method used to determine
the absolute (exact) age of rocks and fossils.
A.D. 1 -used primarily to date igneous rocks
(intrusions)
A.D. 2 -can only date particles in sedimentary rock,
but not the whole rock layer
A.D. 3 - Carbon-14 dating allows scientists to
know the exact (absolute) age of things that were
once living. (You have to know this one.)
Why can radiometric dating only date the
particles in sedimentary rock layers & not the
whole layer?
Let’s do an activity to see how this
works.
Re-cap…Scientists can use radiometric dating
absolute
methods to determine the ___________
age of
igneous
fossils and __________
rocks.
When a new igneous rock forms, it has different
elements in it. Some of the atoms (isotopes) of those
decay
elements are unstable and will “______”(break
down
over time) into atoms of stable elements. The
parent element.
unstable element is called the _______
The stable element is called the ________
daughter element.
Each unstable element has its own unique rate of
decay which is constant. This rate of decay is called a
half-life If scientists know the half-life of an
__________.
element, they can tell how old the rock is based on
how much parent element still remains in the rock and
how much daughter element is present.
Answers at the bottom of your activity:
*As a rock gets older, the amount of parent
(radioactive/unstable) element (1)__________ and
the amount of daughter (stable) element
(2)___________.
An older rock has more (3)________ element, and a
younger rock has more (4)________ element.
With every half-life that passes, the parent
element decreases by (5)________.
After 1 half-life, (6)_____ of the parent element is
present. After 2 half-lives, (7)_______ of the
parent element is present. After 3 half-lives,
(8)______ of the parent element is present.
Let’s watch what Brainpop has to say
about Absolute Dating using a
radioactive substance called Carbon-14.
http://www.brainpop.com/technology/scienceandi
ndustry/carbondating/preview.weml
Let’s practice half-life some more using
a Brainpop activity.
Wrap-up:
What percentage of radioactive –
PARENT- element would remain in a
rock sample after one half-life? Two
half-lives?