ExChild

I have been trying to educate myself on carbon-14 dating and other forms of dating.. In my reading I have seen that 14C dating is accurate to +/- 10%. What I'm wondering is, if something is dated to, say, 10,000 years old, does that mean that it could be off by 1000 years either way? That seems like a lot, so am I missing something? An object that's supposed to be a million years old could really be off by 100,000 years???

I know that a common creationist argument is that 14C dating is not reliable, so any explanation would be appreciated.. with links maybe

Also, I've read that it is living plants and animals that take up 14C in their respiration cycles, and this is what is being measured for dating. So doesn't this mean that things that were never alive, like rocks, can't be dated this way? Is there another method that is used for rocks and stone tablets and such?

Thanks in advance, everyone!

Viti

IIRC C14 dating is only useful to 50,000 years. Other methods are used for things in the millions of years

here's some info
http://www.nunki.net/isis/isisdating.htm
http://pubs.usgs.gov/gip/geotime/radiometric.html
http://www.actionbioscience.org/evolution/benton.html

I googled "Archaeology dating methods" and got tons of hits

malookiemaloo

BY coincidence this subject came up at our church Bible study last night.

The following is probably apocryphal but anyway.

A professor at Dundee university sent various samples from the same piece of rock to a number of universities for dating. Initially he was surprised to be asked to give his own estimate of how old the rock was. For devilment he gave wildly different dates to the universities but was even more surprised to find that the dates given from all the uni's were within the estimate he had given. The result was that the dating of his rock varied by millions of years.

Could this happen?


m

Secular Pinoy

Sounds like a tall tale to me. Since that's probably the best thing young earth creationists can come up with to counter the radiometric dating techniques, I won't be surprised if this story is widespread among YECs.

CX

Seems to me this should be in E/C...

malookiemaloo

There you go pigeon wholing people!!

I wasn't trying to make any sort of case out about the age of the earth. I am not from a science background and therefore could not do so anyway.

Just wondered if the story could be true or not. From what you are saying it is not. Are you quite sure.................?


m

ps418

You mean, is it possible? Yes, its possible, and here's one way it can happen. Consider a very slowly cooling granite pluton (essentially a giant mass of magma) several km under the earth's surface. As it cools, minerals will begin to form sequentially in a particular order known as the Bowen Reaction Series.



The important point is that the high-temp minerals such as plagioclase will reach closure temperature and will start "counting time" long before the low-temp minerals, such as quartz. Therefore, in a slowly-cooled igneous body, there will be a difference in age depending upon which minerals you date. The differences in age will be proportional to the cooling rate of the igneous body.

Joe Meert has a fantastic web article which discusses this phenomenon: Consistent Radiometric Dates. Check out the example of the Carion Pluton in central Madagascar. Particularly, note that when you plot the age of the minerals vrs the mineral's closure temps, it produces a ice cooling curve!



Meert comments:

Patrick

ps418

That's right. 14C dating only works with organic matter.

Absolutely. There are many ways, depending on the object or event you want to date. Examples include K-Ar dating, Ar-Ar dating, U-Pb dating, U-Th dating, electron spin resonance, cosmogenic nuclide exposure dating, thermoluminescence dating, soil-profile development, etc. With 'rocks,' it depends on the kind of rock - not all methods are applicable to all rocks. The best way to date stone tablets would be simple erosion dating -- after all, as an archaeologist you dont want the date of the formation of the stone, but the date of the carving of the stone. For instance, the oldest tombstones in my local cemetary are composed of 400Ma limestone, but the stones were carved about 150 years ago.


Patrick

lpetrich

Seems like some Urban Legend. Has this alleged occurrence ever been documented?

A more likely outcome is something like "We found this rock to have age A. Why did you think it was B?"

Tim Thompson

Radiocarbon Web - All you need to know about carbon dating, from the Waikato and Oxford radiocarbon laboratories.

Radiometric Dating Resource List - The most complete list of web-based resources for learning & understanding the art & science of radiometric dating, at least so far as I know. I created it originally out of frustration at how much time it took to find web resources, and made the list for myself. Then I figured others might find it useful too, and webbed it.

As for precision, radiocarbon dates should typically be ±1% or ±2%. The preliminary dates sent to me, in 1998, for the settlement at Catalhoyuk cluster around 8000±80 uncalibrated years ago. Since then, the calibrated dates I have seen are in the high 7000's of years before present. Last I heard, calibrated radiocarbon dates for the site implied that it was first inhabited circa 8390 years ago, making it the world's oldest city, to the best of my knowledge (Accelerator mass spectrometry dating at Catalhoyuk, E.H. Gokturk, et al., Radiochimica Acta 90(7): 407-410, 2002).