UNIT 5: GEOLOGIC HISTORY

AT THE END OF THIS UNIT YOU WILL BE ABLE TO

Calculate the absolute age of a substance based on its decay rate

Correlate rock layers Create a sequence of events for an

outcrop Obtain information from the

geologic timeline

LABORATORY ACTIVITIES FOR THIS UNIT:

Matching Rock Layers Radioactive Decay Geologic History Timeline Sequence of events

PLEASE ADD THESE TO YOUR TABLE OF CONTENTS IN YOUR NOTEBOOKUnit 5 Geologic History59-61 Geologic history vocabulary62 Ages: absolute and relative63 Radioactive decay: absolute age64 Radioactive isotopes65 Matching/ correlation of rocks66 Order of events

NOW TURN TO PAGE 59 AND NUMBER UP TO PAGE 66

On page 59 at the top please write: Unit 5: geologic history vocabulary

You will be writing out 19 vocabulary words, you may not need up all 3 pages, but I gave you extra room in case you did.

VOCABULARY Absolute age- the actual age, in years of

an event Relative age- the age of a rock or event in

relationship to the age of another rock or event, a comparison

Half life- time required for half of a substance that is unstable to become stable

VOCABULARY

Radioactive dating- the use of a radioactive isotope to calculate the absolute age

Radioactive decay- a breakdown of an unstable atom to a stable atom

Carbon 14 dating- dates organic remains only

VOCABULARY

Uniformitarianism- the present is the key to the past, what happens now happened then 

Superposition- youngest layer is on the top oldest is on the bottom

Original horizontality- rock layers form as horizontal layers

VOCABULARY Unconformity- erosional surface, some

layer has been removed, creates a gap in the timeline

Inclusion- older rock within a younger rock

Extrusion- a mass of igneous rock on the surface, exposed to weathering and erosion, contact metamorphism with the layer below only 

VOCABULARY Intrusion- a mass of igneous rock

formed between layers, contact metamorphism with layers above and below

Contact metamorphism- heat from an igneous rock that changes the rocks around it

Index fossil- used to match layers, must be easy to identify, lived a short time and covered a wide area

VOCABULARY Isotope- a variety of an element

with a different atomic mass, unstable, likes to break down

Correlation- matching Cross cutting relationship- anything

that cuts through is younger Key bed- rock layer that is used to

identify an event or geologic age

EARTH SCIENCE PICTURE OF THE DAY

http://epod.usra.edu/

I. AGES

A.     Absolute ages: Gives you exact numbers 1.  example: your age, the year a car was produced(made)

On page 62 of your notebook

I. AGES

B. Relative age: Comparison of one to another

1. no numbers2. approximate ages

a.  I am older than my brothers

b.  Names of geologic time

On page 62 of your notebook

II. DETERMINING THE AGES (ABSOLUTE AGE)

A.    Radioactive decay or half life1.   Amount of time it takes half the sample to decay or break down into a stable isotope.

a.   paper folding activity

On page 63 of your notebook

II. DETERMINING THE AGES (ABSOLUTE AGE)

B. Radioactive isotopes 1. Carbon -14, organic

materials only (living)a. Examples: cotton, teeth,

bones, trees, bugs, etc…b. Half life: 5.7 x 103 years

On page 64 of your notebook

LAB: RADIOACTIVE MATERIAL?

Everyone needs to wash their hands with soap and water before

we start the lab.

GEOLOGIC MAP OF NYS

Ages Rock names Rock types

young

old

III. MATCHING/CORRELATING LAYERS

A. Key beds: covers everything, marks a time when something BIG happened, it is a time marker.1. Dinosaur extinction: Meteorite impact debris and dust

On page 65 of your notebook

III. MATCHING/CORRELATING LAYERS

B. Other ways to match layers 1.  Fossils, animal remains 2. unconformities: erosional surfaces

3. rock and mineral types

On page 65 of your notebook

Where is the unconformity?

Where is the unconformity?

IV. ORDER OF EVENTS

A.   Principles that we use1. no process has changed

since the earth formed is called Uniformitarianism

2. Sediment layers are always deposited flat,

Original Horizontality

On page 66 of your notebook

Original Horizontality

See the flat layers?

IV. ORDER OF EVENTS

A.   Principles that we use 1. Oldest layers are on the bottom, the youngest are on the top, Superposition

 

On page 66 of your notebook

What layer is the oldest?

What layer is the youngest?

What came first, the Brunswick sandstone or the Palisades sill?

IV. ORDER OF EVENTS

A.   Principles that we use 2.Since the layers are deposited flat

when the layers do not match, something must have happened after they were deposited,

Cross Cutting Relationship a. Faults, Folds, Intrusions,

Extrusions, etc….

On page 66 of your notebook

The horizontal layers had to be deposited first

This was intruded through the layers that were there first.

This is called INTRUSION

See how the layers are

folded over each other

This is extreme

folding that is found often in

mountain areas

More folded layers

The sandstone

layers match and the fault

cuts through them so the layers had to be there

first

As the pressure on the layers increases the folds can only handle so much stress and they break creating a fault.

Look for the faults first!

Match the layers across the faults.

This is an “A”nticline or fold in the rocks