C was mostly incorporated into the seawater from the atmosphere.
If the oceans that the plankton live in are stratified (meaning that there are layers of warm water near the top, and colder water deeper down), then the surface water does not mix very much with the deeper waters, so that when the plankton dies, it sinks and takes away Stable carbon isotopes in carbon dioxide are utilized differentially by plants during photosynthesis.
Carbon-based rocks, such as bitumen and tephra, can also be dated in this manner.
Carbon dating is most effective on material that predates the 1940s; this is due to above-ground nuclear tests increasing the amount of carbon-14 in the environment.
Production rates vary because of changes to the cosmic ray flux caused by the heliospheric modulation (solar wind and solar magnetic field), and due to variations in the Earth's magnetic field.
The latter can create significant variations in The New Zealand curve is representative for the Southern Hemisphere, the Austrian curve is representative for the Northern Hemisphere.
C, or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons.
Its consistent rate of decay allows the age of an object to be determined by the proportion of carbon-14 to other carbon isotopes. Carbon-14 is also used as a radioactive tracer for medical tests.This inconsistent amount of carbon-14 renders the test less accurate but opens up testing possibilities not available for older samples.For example, it is possible to determine the age of a person born after the 1940s using the carbon-14 content of teeth.Atmospheric nuclear weapon tests almost doubled the concentration of The above-ground nuclear tests that occurred in several countries between 19 (see nuclear test list) dramatically increased the amount of carbon-14 in the atmosphere and subsequently in the biosphere; after the tests ended, the atmospheric concentration of the isotope began to decrease.
One side-effect of the change in atmospheric carbon-14 is that this has enabled some options (e.g.Carbon-14 was discovered on 27 February 1940, by Martin Kamen and Sam Ruben at the University of California Radiation Laboratory in Berkeley, California.