# Uranium thorium dating on corals

Radioactive decay occurs when an unstable form of that element changes into a stable one by spinning off a part of its nucleus.Carbon is a useful element for dating objects because it’s so prevalent in our environment.In order to know anything about past climate from corals, we need to know their age.

Fossil corals constrain the timing of past sea level by their suitability for dating and their growth position close to sea level. Uranium and thorium isotope compositions and Rn 222 retentivities were also determined as consistency checks. Atthe number of thorium-230 decays per year within a sample uranium thorium dating corals equal to the number of thorium-230 produced, which also equals the number of uranium-234 decays per year in the same sample. Note that to calculate an age using this technique the ratio of uranium-234 to its parent isotope uranium-238 must also be measured. As a more extensive and rigorous test coals the reliability of He U ages of fossil corals, I have determined Thoriun U ages on forty-five independently dated Cenozoic corals. As time passes after the formation of such a material, uranium-234 in the sample, with a of 245,000 years, decays to thorium-230. As time passes after the formation of such a material, uranium-234 in the sample, with a of 245,000 years, decays to thorium-230. Thorim and Schaeffer 1965 determined He U ages of corals and other aragonitic fossils and found that the results generally agreed with independent age estimates.The unstable form, or isotope, of carbon is 14C; its stable, unchanging isotope is 12C, where the different numbers refer to different atomic weights.As 14C decays, the ratio of 14C to 12C changes over time. We measure the rate of radioactive decay with what’s called a half-life. This means that every 5,730 years, there’s half as much 14C as there was in the previous 5,730-year period.