Scientists use 2 methods to determine the age of fossils: 1. Relative Dating. 2. Absolute Dating. Relative Relative Dating is when you give the age of a rock or fossil compared to another rock or fossil. Example: Rock A is OLDER than Rock B . The textbooks speak of the radiometric dating techniques, and the dates Relative ages are assigned to rocks based on the idea that rock layers lower in the For example, if you began with 1 gram of carbon, after 5, years you clearly supports the idea of a young earth as described by the Bible. Define the difference between absolute age and relative age. Describe four methods of absolute dating. Explain what radioactivity is and give examples of.
If an atom decays by losing a beta particle, it loses just one electron. So what does this have to do with the age of Earth?
High School Earth Science/Absolute Ages of Rocks - Wikibooks, open books for an open world
Radioactive decay eventually results in the formation of stable daughter products. Radioactive materials decay at known rates. As time passes, the proportion of radioactive isotopes will decrease and the proportion of daughter isotopes will increase. A rock with a relatively high proportion of radioactive isotopes is probably very young, while a rock with a high proportion of daughter products is probably very old.
Scientists measure the rate of radioactive decay with a unit called half-life. The half-life of a radioactive substance is the amount of time, on average, it takes for half of the atoms to decay.
For example, imagine a radioactive substance with a half-life of one year. When a rock is formed, it contains a certain number of radioactive atoms. After the third year three half-lives After four years four half-lives6. If you find a rock whose radioactive material has a half life of one year and measure 3.
The decay of radioactive materials can be shown with a graph Figure Decay of an imaginary radioactive substance with a half-life of one year. Radiometric Dating of Rocks[ edit ] In the process of radiometric dating, several isotopes are used to date rocks and other materials.
High School Earth Science/Absolute Ages of Rocks
Using several different isotopes helps scientists to check the accuracy of the ages that they calculate. Carbon Dating[ edit ] Earth's atmosphere contains three isotopes of carbon. Carbon is stable and accounts for Carbon is also stable and accounts for 1.
Carbon is radioactive and is found in tiny amounts. Carbon is produced naturally in the atmosphere when cosmic rays interact with nitrogen atoms.
The amount of carbon produced in the atmosphere at any particular time has been relatively stable through time. Radioactive carbon decays to stable nitrogen by releasing a beta particle. The nitrogen atoms are lost to the atmosphere, but the amount of carbon decay can be estimated by measuring the proportion of radioactive carbon to stable carbon As a substance ages, the relative amount of carbon decreases. Carbon is removed from the atmosphere by plants during the process of photosynthesis.
Animals consume this carbon when they eat plants or other animals that have eaten plants. Therefore carbon dating can be used to date plant and animal remains.
Examples include timbers from an old building, bones, or ashes from a fire pit. Carbon dating can be effectively used to find the age of materials between and 50, years old. Potassium-Argon Dating[ edit ] Potassium decays to argon with a half-life of 1. Because argon is a gas, it can escape from molten magma or lava. Therefore any argon that is found in a crystal probably formed as a result of the decay of potassium Measuring the ratio of potassium to argon will yield a good estimate of the age of the sample.
Relative Dating vs. Absolute Dating: What’s the Difference? – Difference Wiki
Potassium is a common element found in many minerals such as feldspar, mica, and amphibole. The technique can be used to date igneous rocks fromyears to over a billion years old. Because it can be used to date geologically young materials, the technique has been useful in estimating the age of deposits containing the bones of human ancestors. Uranium-Lead Dating[ edit ] Two isotopes of uranium are used for radiometric dating.
Please help improve this section by adding citations to reliable sources. Unsourced material may be challenged and removed. July Thermoluminescence[ edit ] Thermoluminescence testing also dates items to the last time they were heated.
This technique is based on the principle that all objects absorb radiation from the environment. This process frees electrons within minerals that remain caught within the item. Heating an item to degrees Celsius or higher releases the trapped electronsproducing light.
Relative Dating vs. Absolute Dating: What's the Difference?
This light can be measured to determine the last time the item was heated. Radiation levels do not remain constant over time. Fluctuating levels can skew results — for example, if an item went through several high radiation eras, thermoluminescence will return an older date for the item. Many factors can spoil the sample before testing as well, exposing the sample to heat or direct light may cause some of the electrons to dissipate, causing the item to date younger.
It cannot be used to accurately date a site on its own. However, it can be used to confirm the antiquity of an item. Optically stimulated luminescence OSL [ edit ] Optically stimulated luminescence OSL dating constrains the time at which sediment was last exposed to light. During sediment transport, exposure to sunlight 'zeros' the luminescence signal. Upon burial, the sediment accumulates a luminescence signal as natural ambient radiation gradually ionises the mineral grains.
Careful sampling under dark conditions allows the sediment to be exposed to artificial light in the laboratory which releases the OSL signal.