Presentation on theme: "Relative and absolute age dating of rocks. What is absolute age dating? The Principle of Superposition and rock correlation provide the relative ages."— Presentation transcript:
Relative and absolute age dating of rocks
What is absolute age dating? The Principle of Superposition and rock correlation provide the relative ages of rocks. Absolute age dating of rocks gives an actual age (or number) to the rock or outcrop.
Basic atomic chemistry review Element: Made up of atoms that are chemically alike. All atoms consist of protons, electrons and neutrons.
What are atomic numbers and mass numbers for atoms? Mass number: Number of protons and neutrons in an atom. Atomic number: Number of protons in atom. Number of neutrons: Subtract the two values: 12-6=6.
Another example of finding atomic and mass numbers Mass number…85 Atomic number…37 Number of neutrons… = 48
What are isotopes? Isotope: Atoms of the same element which differ only in the number of neutrons in the nucleus. Isotopes are common in most of the chemical elements.
Example of isotopes Carbon is an isotope because it can be either 12 C or 14 C. Carbons atomic number is 6 (from Periodic Table). Therefore, there are 6 neutrons in 12 C and 8 neutrons in 14 C.
Example of an isotope Strontium (Sr) IsotopeProtonsNeutrons 90 Sr Sr3851 Both are atoms of strontium, but each has a different number of neutrons in the nucleus.
Radioactive decay The breakdown of an unstable nucleus into a more stable form. Example Parent isotope (unstable) Daughter product (stable) Parent isotope (unstable) Daughter product (stable)
Half-life The time required for half of a radioactive nucleus to decay into a more stable form. Example: 100% 50% 25% 12.5% 6.25% Start with 100% of a radioactive material
Typical half-life curve As far as we know, nothing can change the half-life of a given radioactive substance.