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Igneous Rocks. Formation, Absolute Age, Radioactive Dating and Unconformities. What is an Igneous Rock?. AKA: Fire Rocks Can be formed underground or above ground: Underground - formed when melted rock called magma Aboveground - formed when volcanoes erupt.
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Igneous Rocks Formation, Absolute Age, Radioactive Datingand Unconformities
What is an Igneous Rock? AKA: Fire Rocks Can be formed underground or above ground: Underground - formed when melted rock called magma Aboveground - formed when volcanoes erupt
What does an Igneous Rock look like? GranitePumice
Determining the Age of an Igneous Rock Think back….How did we determine the age of a sedimentary rock? Can we use the same method for Igneous Rock? Why or Why not? Absolute Age – the process of determining a computed, numerical age
Relative vs. Absolute Age Turn to your shoulder buddy… Quickly discuss the differences between relative and absolute age
Determining Absolute Age Radioactive Dating – using radioactive particles found in a rock to determine the actual age of the rock Radioactivity – the process of rock elements breaking down You can only find these radioactive particles in igneous rocks (does not work with sedimentary rock)
Technology Used to Measure Radioactivity Geiger Counter Ionization Chamber MicroR Meter
Determining Absolute Age Half-life: The breakdown of specific elements happens at a very specific pace Examples: Carbon-14 has a half-life of 5,730 years. Always found in LIVING organisms Potassium-40 has a half-life of 1.3 billion years Using a specific calculation can help you determine the absolute age using half-lives
Determining Absolute Age Half-life: The breakdown of specific elements happens at a very specific pace Examples: Carbon-14 has a half-life of 5,730 years. Always found in LIVING organisms Potassium-40 has a half-life of 1.3 billion years Using a specific calculation can help you determine the absolute age using half-lives
Visuals Help with Radioactive Decay Original Rock 3 Half Lives 4 Half Lives 1 Half Life 2 Half Lives
Practice Time!!! Element Brennan is found in an igneous rock and we are trying to determine the rocks age. We know Brennan’s half life is approximately 3,000 years and that the rock is currently 6.25% radioactive. How old is the rock? Element Brennan is found in an igneous rock and we are trying to determine the rocks age. We know Brennan’s half life is approximately 3,000 years and that the rock is currently 50% radioactive. How old is the rock? Element Brennan is found in an igneous rock and we are trying to determine the rocks age. We know Brennan’s half life is approximately 3,000 years and that the rock is currently 25% radioactive. How old is the rock? 100% Radioactive Igneous Rock 94% decayed 50% decayed 87.5% decayed 50% Radio- active 75% decayed 25% r-a 12.5% 6% Three Half Lives Four Half Lives One Half Life Two Half Lives
LAST PRACTICE QUESTION!!! Last Practice Question: A rock contains a radioactive element with a half life of 100 million years. Tests show that the element in the rock has gone through three half lives. How old is the rock?
Ticket Out the Door • Make a Venn Diagram to compare and contrast absolute and relative age. • Which does radioactive decay fall under? • Which does law of superposition fall under?