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.C (carbon-14) in the upper atmosphere as a result of bombardment by neutrons in so-called cosmic rays: high-energy particles bombarding the Earth's atmosphere from outer space. On formation, the newly-born carbon atom quickly oxidizes to form a molecule of carbon dioxide (COC being produced annually is more or less constant, whereas the quantity being destroyed is proportional to the quantity that exists, it can be shown that the quantity in the atmosphere at any given time will be more or less constant: the processes of production and decay of C, which need not concern us in this article.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.However, the marine component of diet can be estimated by measuring the ratio of the stable isotopes C in the sample: this will be higher the more seafood the individual consumed.This allows archaeologists to estimate the magnitude of this effect and correct for it.The residence time of carbon in the ocean can be measured in hundreds of thousands of years (where the residence time of carbon is defined as the average time an atom of carbon will stay in the ocean).This increases the apparent age of the sample by about 400 years, depending on where in the ocean the organism lived and died.
The result of this is to supply streams, rivers, and lakes with a source of dissolved calcium carbonate; if freshwater shellfish (for example) use this to construct their shells, then they are using a source of carbon which is millions of years old.
Given a latitude and longitude, an appropriate correction to the date is supplied by the Marine Reservoir Database.