Exercise 6 radioisotopic dating techniques
The daughter isotope argon does not start to accumulate until a volcanic eruption takes place, at which point the radioactive decay clock starts.
Over a very long period of time, almost all of the radioactive K will decay to form Ar.
Determining the age of the ash layer will reveal the age of the surrounding ice.
Geologists take advantage of decay of natural radioactive elements to determine the age of rocks, which can help us understand earth history.
Another approach to describing reaction rates is based on the time required for the concentration of a reactant to decrease to one-half its initial value.
This period of time is called the half-life of the reaction, written as .
his document discusses the way radiometric dating and stratigraphic principles are used to establish the conventional geological time scale.
It is not about the theory behind radiometric dating methods, it is about their , and it therefore assumes the reader has some familiarity with the technique already (refer to "Other Sources" for more information).
This plot shows the concentration of the reactant in a first-order reaction as a function of time and identifies a series of half-lives, intervals in which the reactant concentration decreases by a factor of 2.
The dark band in this picture is a layer of volcanic ash trapped in ice from the East Antarctic ice sheet.
The ash was deposited on snow on the surface of the ice sheet, which was then compressed over time to form ice.
The volcanic ash can be dated using a technique called Potassium-Argon (K-Ar) geochronology.
K-Ar geochronology relies on the principal that radioactive elements decay over time, with a parent isotope of potassium (K) decaying to form the daughter isotope argon, (Ar).