Part 4: Radiometric Dating & Radioactivity

Q: Who discovered radioactivity in 1896?

A: Henri Becquerel, by accident with uranium salts and photographic plates.

Q: What did Marie and Pierre Curie discover?

A: Radioactive elements emit heat.

Q: Who explained radioactive decay?

A: Ernest Rutherford and colleagues, ~1904.

Q: Who first dated rocks with U–Pb?

A: Bertram Boltwood, 1907 (~400 Ma to 2 Ga).

Q: Who built the first calibrated geologic time scale with radiometric dates?

A: Arthur Holmes, early 1900s.

Q: What are the three main types of radioactive decay?

A: Alpha (loss of 2p+2n),

Beta (n → p + e–),

Electron Capture (p + e– → n).

Q: What is half-life?

A: Time for half of parent isotopes to decay into daughters.

Q: What is the K–Ar example of radiometric dating?

A: If daughter/parent = 3, and T½ = 1.3 Ga → age ≈ 2.6 Ga.