Relative and Absolute Dating Questions
Draw and describe the 3 types of unconformities.
Angular- Rocks on the bottom are at an angle. Part of them was eroded away, and then new rocks were deposited flat on top of them Nonconformity- Rocks on the bottom have been metamorphosed and melted on top is sedimentary layers Disconformity- Missing layers between flat lying sedimentary rocks
Why would you not use carbon dating for geologic problems?
Because carbon dating does not go far back enough in time to be useful for dating older rocks. Also the carbon surround the fossil or rock could be younger than the rock itself.
Why can't geologists use the ages of sediments from sedimentary rocks to directly determine the age of formation for that sedimentary rock?
Because sedimentary rocks are made up of sediments coming from a variety of different ages, they would be unreliabe to find a close to exact age.
How many protons, neutrons, and electrons does this atom of carbon have? Is it a radioactive isotope?
Carbon has 6 protons, 6 electrons, and 8 neutrons (round mass to whole number, subtract atomic number (6) from mass (14) and get the number of neutrons) It is an isotope, because it has more neutrons in the nucleus than protons.
What is an unconformity, what does it represent?
indicate missing time and are shown with a wavy line.
Why is radiometric dating important?
Radioactive dating is important because it is the main process of determining almost exactly how old a rock sample is. It is one of the best ways to determine how old things are.
Identify 3 major principals/laws of relative dating. For each Principal describe how you tell what is younger and what is older.
Law of Superposition- Rocks on top will be younger than rocks on the bottom Principle of Original Horizontality- Layers of sediment are generally deposited in a horizontal position Rock layers that are flat have not been disturbed Law of cross-cutting- Younger Features cut across older ones Law of Inclusions- An inclusion is a piece of rock that is enclosed within another rock. Rock containing the inclusion is younger
What does the principle of original horizontality state? How would it be used
Layers of sediment are generally deposited in a horizontal position Rock layers that are flat have not been disturbed. This can be used to determine if rocks in a given time period have been disturbed.
What material is used to date the age of the Earth? Why not just use rocks found on earth?
Mainly meteorites are used to determine the age of the earth because they are not being changed, and weren't being changed in space before they crashed into earth. The earth is a constantly changing object, and the rocks that exist on the planet now are highly unlikely to be the original rocks they were billions of years ago.
What is the upper-limit of Carbon Dating? (Multiply the half-life by 9)
So little radioactive carbon is left after 9 half lives (51570 years) that we often don't measure things older than that with carbon.
The Jackson Hills Zircons are considered very important geological and biological, why?
The jackson Hills Zircons were zircons that were preserved and haven't been changed, so they are very useful for various forms of dating
A piece of pottery contains 12.5 grams of radioactive carbon and 87.5 grams of non-radioactive nitrogen. How old is the pottery? [Note: Carbon has a half-life of 5730 years]
The pottery is approximately 17190 years old. (Underwent 3 half lives, 3 x 5730 = 17190)
