Absolute Ages of Rocks Answers

Relative age compares the ages of rocks or fossils without determining an exact number of years, while absolute age gives a numerical age or age range in years.

After each half-life, half of the remaining parent material decays into daughter material: 50% parent after 1 half-life, 25% after 2, 12.5% after 3, and 6.25% after 4. The rest is daughter material.

Scientists can use radiometric dating, which measures the amounts of radioactive parent isotopes and daughter products in a rock.

Half-life is the time required for half of a radioactive element’s atoms to decay. By measuring how much parent isotope remains and how much daughter product has formed, a geologist can determine the age of a rock or fossil.

20 g of parent material and 60 g of daughter material.

Initially the sample contains 100% parent material. After each half-life, half of the remaining parent material decays into daughter material: 50%/50% after 1 half-life, 25%/75% after 2, 12.5%/87.5% after 3, and 6.25%/93.75% after 4. After many half-lives, nearly all is daughter material.

Alpha decay occurs when an unstable nucleus emits an alpha particle made of two protons and two neutrons, reducing its atomic number by 2 and its mass number by 4.

Radioactive decay is the spontaneous breakdown of an unstable atomic nucleus, releasing radiation and forming a more stable daughter isotope or element.

Carbon-14 is useful for dating relatively recent fossils, generally up to about 50,000–60,000 years old. It is not useful for fossils that are millions of years old because nearly all the carbon-14 has decayed.

Beta decay occurs when a neutron changes into a proton and emits a beta particle, usually an electron. The atomic number increases by 1, but the mass number remains unchanged.