Volcanoes, Earthquakes, Tsunamis What do you know? What are some things you want to learn or...
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Transcript of Volcanoes, Earthquakes, Tsunamis What do you know? What are some things you want to learn or...
Volcanoes, Earthquakes, TsunamisWhat do you
know?What are some
things you want to learn or questions you have?
Early History of Earth• Formation by collision of
material in the solar system–4.6 billion years ago
• Bombarded with asteroids early on caused surface to be molten
• Gradually cooling• 3.9 billion yrs.–Oceans formed
High iron content Brown color– Atmosphere
• Mostly carbon dioxide
• Pink in color
Daily Review #11. Describe an organism that could have
survived on Earth 3.9 billion years ago.2. Approximately how old is Earth?3. You are out hiking or walking along a
path and notice a section rock like in the picture below. What questions would you have about that section of rock?
Absolute Dating Aka: radiometric or
isotopic dating Tells an “exact” age Radioactive decay
◦ Parent nucleus becomes more stable daughter nuclei
◦ Give off energy◦ Constant rate
Half-life◦ 100g → 50g + 50g◦ → 75g + 25g
How do scientists use it? % parent left = # of half-lives → age What do we use?
◦ Carbon-14◦ Uranium-235◦ Potassium-40
Carbon Dating
Various forms of carbon◦ Most common = carbon-12◦ Radioactive = carbon-14
Carbon-14◦ Used for things that were
alive◦ During life - constantly
replaced◦ After death - amount starts
to decrease◦ Half-life of 5,730 years
Half-Life Fraction carbon -14 left
Percentage carbon-
14 left
Age
1
2
3
4
You are a CSI Detective…• You found a skeleton contains 12.5%
of its original carbon.1. How many half lives have passed?2. How old is it? (how long ago did this
person die?)
You are an anthropologist and found this animal!
• This skeleton contains 3.125% of its original carbon.1. How many half lives have passed?2. How old is it?
Daily Review #24. What happens in radioactive decay?5. Define half-life.6. The element chaparralium has a half-
life of 24,000 years. If a fossil contains 25% of the original amount of chaparralium, how old is this fossil? Explain how you arrived at this answer.
7. What do you think happened to create the rock in this picture?
Relative Dating
Order of events
X is older/younger than Y
Less specificThree major
techniques
Where is the oldest part of your ice cream sundae?
How are rocks similar?◦Law of superposition Oldest… Youngest…
◦Principle of horizontality
What if the layers aren’t horizontal?Happened after
rock cooledFolding
◦Caused by pressure
Cross-CuttingOccur after
rocks formFaults
◦Caused by earthquakes
◦Shift rock layers
Cross-Cutting cont.Intrusions
◦Magma invades cracks
◦Cools into rock◦Younger than
surrounding rock
Tell the rock’s story…