Topic: Absolute Dating

Absolute Dating is the real, true age of the rock

Examples - Tree Rings

Varves •Layers of sedimentary rock that were formed in a lake from season to season

Radioactive Dating – -

Absolute Dating

Radioactive elements decay steadily. 1. -2. -3. -4. -5. -

Examples Front of ESRT

Parent IsotopeDaughter Isotope

# of Half-Lives Half-Life of Carbon-14

Age of Rock (years old)

% of Carbon Remaining

% of Nitrogen

0

1

2

3

4

5

6

Example of Half Life• Your rock contains 3

grams of C14 and 9 grams of N14. How old is your rock?

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Example of Half Life

• A sample of wood that originally contained 100 grams of carbon 14 now only contains 25 grams of carbon 14. Approximately how many years ago was this sample part of a living tree?

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Example of Half Life

• A rock contains 5 grams of Uranium 238 and 35 grams of Lead 206. How old is the rock?

• -

Example of Half Life

• A fossil contains 5 grams of carbon 14 and 75 grams of Nitrogen 14. How old is the fossil?

• -

Final Question:• A rock containing Potassium 40

undergoes 3 half lives, what is the age of the rock?

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Topic: The Earlier Earth

Law of Uniformitarianism

“The present is the key to the past.”

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Earth is a Dynamic and Evolving Planet

• Changes in its surface

• Changes in life

Origin of Our Solar SystemSolar nebula theory

The Planets

• Planetesimals have formed in the inner solar system, and large eddies of gas and dust remain far from the protosun.

• -

Sun and Rotating Cloud

How old is the Earth?

• 4,600,000,000 = -

An Early Earth• -• Heat sources:

• -• -• -

• -

Earth’s Differentiation• Early Earth – -

• -

• Lighter silicates flowed up to form mantle and crust.

Why?

The Moon• -

Earlier Earth Atmosphere• -

Ocean Formation• -

Exploring Geologic Time

What has been around for a long time to help geologist study the Earth?

Final Question:

• The geologic history of an area can best be inferred by studying

A) erosional processes affecting the area

B) plants and animals now living in the area

C) present climatic conditions of the area

D) bedrock compositions and rock structures in the area