AP BIOLOGY

Detailed explanation-1: -Of the three basic rock types, igneous rocks are most suited for radiometric dating. Metamorphic rocks may also be radiometrically dated. However, radiometric dating generally yields the age of metamorphism, not the age of the original rock.

Detailed explanation-2: -Uranium-Lead Dating Two isotopes of uranium are used for radiometric dating. Uranium-238 decays to form lead-206 with a half-life of 4.47 billion years. Uranium-235 decays to form lead-207 with a half-life of 704 million years. Uranium-lead dating is usually performed on crystals of the mineral zircon (Figure 11.26).

Detailed explanation-3: -Measuring the ratio of potassium-40 to argon-40 will yield a good estimate of the age of the sample. Potassium is a common element found in many minerals such as feldspar, mica, and amphibole. The technique can be used to date igneous rocks from 100, 000 years to over a billion years old.