Radio active isotope techniques sediment dating
After the organism dies, carbon-14 continues to decay without being replaced.To measure the amount of radiocarbon left in a artifact, scientists burn a small piece to convert it into carbon dioxide gas.
While not a chemical test, the presence of carbon in a sample (like a meteorite) can be found by vaporizing the sample and passing it through a mass spectrometer.Radiocarbon dating estimates can be obtained on wood, charcoal, marine and freshwater shells, bone and antler, and peat and organic-bearing sediments.They can also be obtained from carbonate deposits such as tufa, calcite, marl, dissolved carbon dioxide, and carbonates in ocean, lake and groundwater sources.The method was developed immediately following World War II by Willard F.Libby and coworkers and has provided age determinations in archeology, geology, geophysics, and other branches of science.Radiation counters are used to detect the electrons given off by decaying C-14 as it turns into nitrogen.
The amount of C-14 is compared to the amount of C-12, the stable form of carbon, to determine how much radiocarbon has decayed, thereby dating the artifact.
Exponential Decay Formula: A = A" is the original amount of the radioactive isotope that is measured in the same units as "A." The value "t" is the time it takes to reduce the original amount of the isotope to the present amount, and "k" is the half-life of the isotope, measured in the same units as "t." The applet allows you to choose the C-14 to C-12 ratio, then calculates the age of our skull from the formula above.
We have rocks from the Moon (brought back), meteorites, and rocks that we know came from Mars.
When we age date a planet, we are actually just dating the age of the surface, not the whole planet.
We can get absolute ages only if we have rocks from that surface.
For others, all we are doing is getting a relative age, using things like the formation of craters and other features on a surface.