How to Date a Dead Thing
Understanding Geologic Time/ Focus Questions Key
Some minerals in rocks and organic matter (e.g., wood, bones, and shells) can contain radioactive isotopes. The abundances of parent and daughter isotopes in a sample can be measured and used to determine their age. This method is known as radiometric dating. Some commonly used dating methods are summarized. I am by no means an expert in the many radiometric means of dating rock, but one of the systems often used (and the one I believe your teacher was speaking of) is potassium-argon dating. Rocks with potassium content will contain some primordial level of radioactive K at the time of their formation. 7 Jan what-can-radiometric-dating-tell-you-about-the-ag: what can radiometric dating tell you about the age of rocks that the law of superposition cannot.
In practice, I'm not sure how one would calibrate this for rocks. I've always been told that we can determine rocks' formation time via radiometric dating. This implies that something about the radioisotope abundances are known or assumed at the time of formation.
Http://minimoving.info/lub/what-is-the-most-popular-dating-site-in-the-uk.php have said that rocks' "internal clocks" reset when they form. Suppose you take a 1 Gya rock, melt it in a furnace, and then let it re-freeze. According to what I've heard, the rock's "internal clock" has now reset, which implies that its radiometric abundances are the same as when it first formed.
This doesn't make sense: How, then, would one be able to distinguish its date of formation? I am by no means an expert in the many radiometric means of dating rock, but one of the systems often used and the one I believe your teacher was speaking of is potassium-argon dating.
What can radiometric dating tell you about the age of rocks
Rocks with potassium content will contain some primordial level of radioactive K at the time of their formation. That stuff has a half-life of 1.
Fossils occur for a distinct, limited interval of time. U leakage would cause discordant points to plot above the cocordia. Thus, radiocarbon dating is only useful for measuring things that were formed in the relatively recent geologic past.
Potassium is beta active and decays to argon Which is a gas. So it doesn't bind chemically to other atoms in it's environment and will escape if not confined. If that decay happens in a solid context the argon is trapped, and a scientist can put a small sample of the potassium bearing mineral from the rock through a mass spectrometer to measure the ratio of K to Ar present, and from that determine how long it has been since the rock was last in liquid form.
Because gaseous argon moves quite easily through molten rock and will escape from the immediate neighborhood of its potassium progenitors. Other radiometric dating schemes for geological samples may not have the property where the daughter isotope is a noble gas.
Join them; it only takes a minute: Here's how it works: Anybody can ask a question Anybody can answer The best answers are voted up and rise to the top. Why does radiometric dating tell us the ages of rocks?
What can radiometric dating tell you points 1 · GitBook
I understand well how radiometric dating works in theory. I believe in radiometric dating you compare the amount of radioactive isotope to the amount of decay products "daughter isotopes". The idea behind the reset is that during "melting" or at least heatingthe daughter isotopes are rejected from some materials. Sign up or log in Sign up using Google.
How Does Radiocarbon Dating Work? - Instant Egghead #28
Sign up using Facebook. Sign up using Email and Password. Post as a guest Name.
Second, it is possible to determine the numerical age for fossils or earth materials. I am by no means an source in the many radiometric means of dating rock, but one of the systems often used and the one I believe your teacher was speaking of is potassium-argon dating. Because they are often rare, primate fossils are not usually good index fossils. For example, based on the primate fossil record, scientists know that living primates evolved from fossil primates and that this evolutionary history took tens of millions of years.