Dating Notes

I will be able to identify which methods are best for determining the ages of various materials

Talk with your neighbor

• What might you want to Date in Earth Science?

• What are two ways of Dating things?

I will be able to identify which methods are best for determining the ages of various materials

Relative Dating

You are identifying if something is older or younger than something else

I will be able to identify which methods are best for determining the ages of various materials

Stratigraphy

I will be able to identify which methods are best for determining the ages of various materials

I will be able to identify which methods are best for determining the ages of various materials

What is older? B or C

I will be able to identify which methods are best for determining the ages of various materials

What is older? G or A

I will be able to identify which methods are best for determining the ages of various materials

What is Oldest?

I will be able to identify which methods are best for determining the ages of various materials

What is youngest?

I will be able to identify which methods are best for determining the ages of various materials

Fossil Evidence

I will be able to identify which methods are best for determining the ages of various materials

Absolute Dating

• Dendrochronology

I will be able to identify which methods are best for determining the ages of various materials

Dendrochronology

I will be able to identify which methods are best for determining the ages of various materials

What are some limitations to Dendrochronology?

What are three benefits?

Radiometeric Dating

• Use decay of radioactive isotopes

• Decay happens at predictable rate– Uranium 235– Potassium/ Argon– Carbon Dating

Radiometeric Dating video

I will be able to identify which methods are best for determining the ages of various materials

Review Atoms

• Nucleus composed of protons (p+) and Neutron (n0)

• Electrons (e-) fly around nucleus in different energy levels

• Elements are decided by the number of protons an atom has.

I will be able to identify which methods are best for determining the ages of various materials

• Atomic Symbol• Atomic Number• Number of Protons• Number of Electrons (if

Neutral)• Atomic Weight (p++n0)

I will be able to identify which methods are best for determining the ages of various materials

CFU• Find the number of protons, electrons, and

neutrons for the following

So why the decimal

• The atomic weight has a decimal because it is the average weight of all the naturally occurring isotopes.

• What is an Isotope?• A different “version” of an element. Isotopes

vary by the number of neutrons they possess.• Ex: C-12, He-3, U-238

I will be able to identify which methods are best for determining the ages of various materials

Radiometric Dating

• Radioactive Decay• Half-life.• The half life is the

amount of time it takes for half of Isotopes to change from the original form (parent isotope) to the new form (daughter isotope).

What is Uranium 235’s Daughter isotope?

I will be able to identify which methods are best for determining the ages of various materials

Let us illustrate our idea

• Ex: Carbon-14 with a half-life of 5,730years (we’ll call it 6,000)

My so called half-life

What things can you date with Radio Carbon Dating?

I will be able to identify which methods are best for determining the ages of various materials

Compare Uranium 235 dating to Radiocarbon dating.

Potassium Argon

40K decays into 40Ca and 40Ar

Half life is 1.248×109

Magnetic field Reversals

Reversals in earth’s magnetic field trapped in lava flows at ocean ridges

Are the magnetic field reversals Relative or Absolute Dating?

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