1. Lecture 5: In the Beginning: Radiometric Dating 1.The Age of the Earth 2.Radiometric dating - early chronology

2. Meteorites - the stories they tell The Meteorite “Allende” (fell in 1969, Mexico) is ~30 Ma older than the Earth, and has isotopes from a Supernova that exploded ~4.60 Ga ago !

3. The Oldest Rocks on Earth The age of our Sun Sun’s age = 4 560 million years (= 4.56 Ga) helioseismology The age of our Earth Earth’s age = 4 530 million years radiometric dating of rocks

4. The Formation of the Earth Precise timeline of early events.

6. Radiometric Dating Radioactive 40 K decays to 40 Ar. Half-life: 1.25 Ga.

7. The Periodic Table

8. Radiometric Dating

9. Radioactive 238 U decays to 206 Pb. Half-life: 4.5 Ga.

10. Radiometric Dating This zircon is 3.458 Ga old, and so are the rocks in which it was.

11. Main points to take home: 1) The Earth formed ~30 Myr after the Sun, about 4 530 Myr ago 2)Radioactive decay - a reliable chronometer.