ESS102H1 Chapter Notes - Chapter 7: Unconformity, Metamorphic Rock, Relative Dating
Document Summary
Angular unconformity: consists of tilted or folded sedimentary rocks that are overlain by younger, more flat-lying strata; indicates that a period of deformation and erosion has occurred. Disconformities: sometimes this method is difficult to apply since underlying layers may or may not be older or younger than the since the rocks are similar. Using this method to date requires the counting of the number of parent and daughter products aka radiometric dating. The time required for half of the nuclei in a sample to decay is called the half-life of the isotope. Five particular radioactive isotopes have proved useful for dating ancient rocks: rubidium-87, thorium-232, and the two isotopes of uranium are only used to date rocks that are millions of years old, but potassium-40 is more versatile. Sources of error: accurate date can only be obtained if the mineral remained in a closed system during the entire period since it formed.
