Volcanoes, Earthquakes, TsunamisWhat do you

know?What are some

things you want to learn or questions you have?

Early History of Earth• Formation by collision of

material in the solar system–4.6 billion years ago

• Bombarded with asteroids early on caused surface to be molten

• Gradually cooling• 3.9 billion yrs.–Oceans formed

High iron content Brown color– Atmosphere

• Mostly carbon dioxide

• Pink in color

Daily Review #11. Describe an organism that could have

survived on Earth 3.9 billion years ago.2. Approximately how old is Earth?3. You are out hiking or walking along a

path and notice a section rock like in the picture below. What questions would you have about that section of rock?

Absolute Dating Aka: radiometric or

isotopic dating Tells an “exact” age Radioactive decay

◦ Parent nucleus becomes more stable daughter nuclei

◦ Give off energy◦ Constant rate

Half-life◦ 100g → 50g + 50g◦ → 75g + 25g

How do scientists use it? % parent left = # of half-lives → age What do we use?

◦ Carbon-14◦ Uranium-235◦ Potassium-40

Carbon Dating

Various forms of carbon◦ Most common = carbon-12◦ Radioactive = carbon-14

Carbon-14◦ Used for things that were

alive◦ During life - constantly

replaced◦ After death - amount starts

to decrease◦ Half-life of 5,730 years

Half-Life Fraction carbon -14 left

Percentage carbon-

14 left

Age

1

2

3

4

You are a CSI Detective…• You found a skeleton contains 12.5%

of its original carbon.1. How many half lives have passed?2. How old is it? (how long ago did this

person die?)

You are an anthropologist and found this animal!

• This skeleton contains 3.125% of its original carbon.1. How many half lives have passed?2. How old is it?

Daily Review #24. What happens in radioactive decay?5. Define half-life.6. The element chaparralium has a half-

life of 24,000 years. If a fossil contains 25% of the original amount of chaparralium, how old is this fossil? Explain how you arrived at this answer.

7. What do you think happened to create the rock in this picture?

Relative Dating

Order of events

X is older/younger than Y

Less specificThree major

techniques

Where is the oldest part of your ice cream sundae?

How are rocks similar?◦Law of superposition Oldest… Youngest…

◦Principle of horizontality

What if the layers aren’t horizontal?Happened after

rock cooledFolding

◦Caused by pressure

Cross-CuttingOccur after

rocks formFaults

◦Caused by earthquakes

◦Shift rock layers

Cross-Cutting cont.Intrusions

◦Magma invades cracks

◦Cools into rock◦Younger than

surrounding rock

Tell the rock’s story…