answer at once.. please...
2006-07-30 13:09:44 · 7 answers · asked by ksha_xprx 1 in Science & Mathematics ➔ Earth Sciences & Geology
They measure the decay rate of certain isotopes in the rock.
2006-07-30 13:13:46 · answer #1 · answered by Anonymous · 0⤊ 0⤋
They assume that there is a certain element in the rock at the time of the rock's formation. Then they know that the rock will through time decay into another element. By measuring the new element formed by the decay, they can measure how long it took to reach that percentage of the new element. For example, rubidium decays into strontium, and the amount of strontium shows the length of time the rock decayed by knowing the decay rate (half-life) of rubidium. The trouble with the process is that it is based on an assumption that there was none of the decay element in the original rock and that nothing has affected the rate of decay. It is a dangerous thing to assume anything, in science, but they do. Half-lives, for example, are affected by levels of radiation, and atmospheric pressure and magnetic fluctuations can also alter half-lives.
2006-07-30 23:04:49 · answer #2 · answered by Anonymous · 0⤊ 0⤋
There are several types of radiometric dating that may be employed to measure the age of rocks. See the Wikipedia entry for details (reference 1).
Indirect use of half-life may employ fission track dating; a link for additional information on that may be found in the same URL.
2006-07-30 20:13:57 · answer #3 · answered by Anonymous · 0⤊ 0⤋
any substance contains isotopes which are radioactive. These isotopes decay over time, the time taken for the no of isotope atoms to halve remains the same. Therefore by measuring the proportion of isotopes present, we can determine the age of that substance
2006-07-31 02:17:45 · answer #4 · answered by Danushka B 2 · 0⤊ 0⤋
Because they know that radioactive isotopes decay into other isotopes at predictable rates. They know what the beginning percentage of isotopes was. They measure what it is now. From that they get the age.
2006-07-30 20:15:07 · answer #5 · answered by helixburger 6 · 0⤊ 0⤋
take uranium for example it will slowly decay at an expotidional rate of 50% into lead if you have a small amout in your rock you can tell when it originated
this type of dating can only go so far into the past
2006-07-30 20:23:20 · answer #6 · answered by Anonymous · 0⤊ 0⤋
they use radio activity
2006-07-30 20:20:04 · answer #7 · answered by tan_kaa_milan 3 · 0⤊ 0⤋