Tuesday, April 2nd Warm-Up Agenda Homework Choose ONE question: What is an index fossil? How do index fossils show us the relative age of rock layers? What can index fossils be used to help prove? Agenda Notes on Absolute Age, Radioactive Dating and Ice Cores Homework Part 2 Vocab – Due Friday 4/5

Absolute Age and Radioactive Dating

Absolute Age of Rocks How can scientists determine the exact age of rocks?

Absolute Age of Rocks How can scientists determine the exact age of rocks? Radioactive Dating The process of measuring the known rate of decay of radioactive materials contained in the rocks.

Radioactive Decay Radioactive Decay - the process in which a radioactive isotope tends to break down into stable atoms of the same element or another element.

What are Isotopes? Isotope - an atom that has a different number of neutrons than stable atoms of the same element. Carbon 12 Carbon 14

Carbon Dating Video http://www.pbs.org/wgbh/nova/tech/radiocarbon-dating.html

Radioactive Decay - Isotopes Parent Isotope - The original radioactive element. Daughter Isotope - The stable isotope that results from radioactive decay of the parent isotope.

Half-Life Half-Life - The time needed for half of a sample of radioactive substance to undergo radioactive decay. The time it takes for the Parent Isotope to break down into the Daughter Isotope.

Half-Life Activity Using the scissors, cut the piece of paper in half. Every time you cut the paper, that is one Half-Life. See how many times you can cut the paper in half.

Half-Life of Different Elements

Calculating Half-Life Time (years) % of Carbon-14 100% 1 5730 50% 2 3 4 5

Calculating Half-Life Time (years) % of Carbon-14 100% 1 5730 50% 2 11460 25% 3 4 5

Calculating Half-Life Time (years) % of Carbon-14 100% 1 5730 50% 2 11460 25% 3 17190 12.5% 4 5

Calculating Half-Life Time (years) % of Carbon-14 100% 1 5730 50% 2 11460 25% 3 17190 12.5% 4 22920 6.25% 5

Calculating Half-Life Time (years) % of Carbon-14 100% 1 5730 50% 2 11460 25% 3 17190 12.5% 4 22920 6.25% 5 28650 3.125%

Calculating Half-Life Example: Carbon-14 has a Half-Life of 5730 years. How many years old would a fossil be if it contained 6.25% of Carbon-14?