# age is relative 2

The question of age can be applied to humans, clothing, food, furniture, and fossils. Doctors study how humans age and can observe how hair turns grey and skin becomes wrinkled. Rocks and other organic materials do not always provide observers the same outward changes. In order to determine the age of a material; including human bones, radiometric dating can be applied. Determining the amount of radioactive isotopes in a geological or archeological specimen can help decipher its relative age. Since all rocks and minerals contain radioactive elements, the decay process is like a clock that a geologist can read since different radioactive elements have independent “clocks” or half-lives. Read more about radiometric dating in your textbook.

For this unit, answer the following questions:

1. Pick TWOof the following and describe how radiometric dating has been utilized to determine their age:
1. Earth
2. Moon
3. Meteorites
4. Fossils
5. Early man
6. Historic relics (i.e., Dead Sea Scrolls, Shroud of Turin)
7. Volcanic eruptions
2. Identify one element used to date rocks and minerals. How long is its half-life?
3. How can radioactivity be measured?
4. Rocks, minerals, and even food we eat can contain radioactive material. Why doesn’t this radioactive material comprise a threat to humans?
5. What is an alternative method to radiometric dating? What are the strengths and weaknesses to this type of dating process?

Just response each posted down below # 1 to 3 only

Posted 1

To determine the age of a rock or fossil, researchers use a type of clock to find out the date when the fossil was formed. Geologists use radiometric dating methods, based on the radioactive decay of some elements in order to date events that happened a long time ago. Dating the age of Early Man uses the principle of radiometric dating. Living things exchange carbon in the environment until they die. At death, this stops and the Carbon-14 decays with a half-life and then scientists can calculate the time of death. A negative of this is atmospheric carbon variations leaves this method unreliable. They now have improved it to make it more reliable. Potassium 40 is an element used to date rocks. It’s half-life is 1.3 billions years. The units of measure for radioactivity are the curie and becquerel. Exposure shows the amount of radiation going through the air. Four different units are exposure, absorbed dose, and dose equivalent. Radioactivity is the amount of radiation released. Exposure is the amount of radiation going through the air. Absorbed dose is the amount of radiation absorbed by an object or a person. Dose equivalent is a mixture of the amount of radiation absorbed and the medical effects of that type of radiation. Radioactive material is not a threat to human beings because there is radioactivity in everything that we encounter but it is in such small doses that it is not harmful. There is radon in the air, the water we drink, and the food we eat. An alternative method to radioactive dating is potassium- argon dating that is useful for rocks over 100,000 years old. A strength is that it can date back to rocks that are thousands and thousands of years old. A weakness is that it only works if a rock shows no evidence of having gone through a heating-recrystallization process after it is formed.

Posted 2

Good afternoon Professor and classmates,

• Radiometric dating is way of dating objects like rocks, relics, even volcanoes by using the radioactive rate of decay of a known isotope. I decided to look into the Dead Sea Scrolls, which are various scrolls discovered in caves along the western shore of the Dead Sea, beginning in 1947. The “Khirbet Mird” was a scroll written on papyrus and scientists have dated it AD 675-765. The “Apoeryphon Thanksgiving” was written on parchment, and it has been dated BC-AD 61. In both cases, small samples were taken from the scrolls, treated with a chemical process to determine the carbon half-life. The volcanoes on the Galapagos Islands were able to be dated using instead the half-life of Helium-3 instead of carbon. Using a mass spectrometer, scientists discovered that the Fernadina volcano is less than 4,000 years old!
• Tritium’s half-life, 12.38 years, is also measured by the buildup of Helium-3.
• A Geiger counter is used to measure radioactivity. The unit for measuring radioactivity is a becquerel (Bq), and it indicates the rate of decay per second.
• We are surrounded by low levels of radioactivity in many things around us, even in some of our food. The levels are generally very low, and won’t have a serious impact on human health unless exposure happens over a very long period of time or if the levels are very high.
• According to Tarlach, (2016), Biostratigraphy is a method used by scientists to date things like fossils, based on the layers of surrounding rocks. The advantages of this system are that it is easy to understand, and does not require researchers to damage the item by taking a sample of it to date. The problem with this system of dating is that it is not as accurate as radiometric dating.

Posted 3

Hello everyone

According to our text Trefil & Hazen, 2016 explains, when trying to determine the age of fossils and or early man by using radiometric dating, one must measure the amount of “carbon-14” that is still present in the tissue or bones. Also mentioned, throughout one’s life we absorb carbon and any other living organism for that matter takes in carbon. (p 275) Our text best explains how and which minerals and which element is used to date rocks, for example; “scientists must rely on similar techniques that use radioactive isotopes of much greater half-life. Among the most widely used radiometric clocks in geology are those based on the decay of potassium-40 (half-life of 1.25 billion years), uranium-238 (half-life of 4.5 billion years), and rubidium-87 (half-life of 49 billion years). In these cases, we measure the total number of atoms of a given element, together with the relative percentage of a given isotope, to determine how many radioactive nuclei were present at the beginning.” (p 276)

The measurement of radioactivity goes to Marie Sklodowska Curie (1867-1934), our text Trefil & Hazen, 2016 explains, Curie, worked with many “exotic uranium-bearing minerals. She had been able to isolate minute quantities of unknown minerals such as radium and polonium. Of which her crowning glory when she was able to isolate “22 milligrams of radium chloride” which is now widely used to measure radiation levels. (p 270) The food we eat, rocks,minerals that has radioactive materials in them is not harmful to us because it is in small doses and according to our text which explains radiation has been a part of our natural environment from the beginning and then we ourselves and all living organisms was able to evolve and flourish in a radioactive environment. (p 273) It is all a part of us. An alternative method of radiometric dating is known as “Potassium-Argon dating”. Based on our reading, it was used to determine the age of skulls found in rocks; by dating the rocks Scientists was able to date the skulls. The skulls were found to be around 3.7 million years old. ( p 276, figure 12-12)