Uranium–lead dating

Uranium–lead dating estimates the time since minerals crystallized by measuring radioactive uranium isotopes and their lead decay products. Its two independent decay chains help reveal whether a mineral remained a closed system.

Uranium-238–lead-206 decay chain: The radioactive sequence in which uranium-238 ultimately decays into stable lead-206. This chain supplies one of the two independent clocks used to calculate an age.
Radioactive decay: The spontaneous transformation of unstable atomic nuclei into more stable products. Uranium–lead ages rely on predictable nuclear transformations over geological time.
Geologic time scale: A chronological framework that divides Earth's history into named intervals based on rocks, fossils, and geologic events. Uranium–lead dates help anchor boundaries and events deep in Earth's history.
Rubidium–strontium dating: A radiometric method that estimates age from the decay of rubidium-87 into strontium-87. It uses a different parent–daughter system and can date minerals with little or no uranium.
Arthur Holmes: A British geologist who used radioactive decay to estimate the ages of rocks and Earth's history. His early uranium-based calculations helped establish radioactive dating as a geological tool.
Uranium-235–lead-207 decay chain: The radioactive sequence in which uranium-235 ultimately decays into stable lead-207. Its age can be compared with the uranium-238 chain as an internal consistency check.
Radiometric dating: A method of determining age from measured proportions of radioactive isotopes and their decay products. Uranium–lead dating is one member of this broader family of age-determination methods.
Jack Hills zircon: A detrital zircon from Western Australia's Jack Hills, dated to about 4.4 billion years old. Its uranium–lead age provides evidence for very ancient continental crust on Earth.
Potassium–argon dating: A radiometric method that estimates age from the decay of potassium-40 into argon-40. Unlike uranium–lead dating, it measures a gas daughter that can escape when rocks are heated.
Bertram Boltwood: An American chemist who demonstrated the relationship between uranium and lead in radioactive minerals. His work helped establish lead as the end product for uranium-based geological dating.

Linked from 35 pages