Methods Of Dating Rock & Fossils

[idscience]

What are they, What lengths of time are they acurate to?

 

[Nabobalis]

Here is a Wikipedia article:

Radiometric dating - Wikipedia, the free encyclopedia

 

[Incariol]

What are they, What lengths of time are they acurate to?

Off the top of my head, methods go from a few thousand years out to several billion.

 

[idscience]

Here is a Wikipedia article:

Radiometric dating - Wikipedia, the free encyclopedia

thanks

 

[juvenissun]

What are they, What lengths of time are they acurate to?

People measure the abundance of different atoms in some earth material, and calculate the time during which these atoms changed their abundance. They called the calculated value to be the "age" of the material. A pair of special atoms work at a time. They called the different pairs of atoms as different "methods".

The calculated number ranges from thousands to billions. The reported good accuracy is something like ± 2%

 

[idscience]

How do scientists deside how much radiation was in the rocks to begin with, so they can decide percentage of rate of decay?

How do they know decay is a constant rate over billions of years?

How do they know nothing has interfeared with the rate of decay over the billions of years?


2% accuracy still gets you into the tens of millions of years out, and I would like to know how they verify the acuracy? Sounds a bit sketchy to me.

 

[Split Rock]

How do scientists deside how much radiation was in the rocks to begin with, so they can decide percentage of rate of decay?

There is no "radiation" in the rocks. You probably mean starting daughter isotopes. Isochron dating makes no assumptions about starting daughter isotopes and can be used to determine if there were any to begin with.

How do they know decay is a constant rate over billions of years?

All evidence infers this, including examination of distant stars.

How do they know nothing has interfeared with the rate of decay over the billions of years?

Only under extreme physical conditions is there any change in the decay rate.

2% accuracy still gets you into the tens of millions of years out, and I would like to know how they verify the acuracy?

The accuracy is determined by replication, and the technique used. Also, 2% error doesn't get you anywhere near to 6,000 years.

Sounds a bit sketchy to me.

What sounds sketchy? You've barely looked at any details.

I thought IDers had no problem with Deep Time, since they weren't creationists (ha, ha).

 

[RocksInMyHead]

How do scientists deside how much radiation was in the rocks to begin with, so they can decide percentage of rate of decay?

As Split Rock said, there is no "radiation" in the rocks. What can throw off age calculations are excess daughter isotopes (decay products) that were not produced by the original parent isotopes in the rock. The effects of this are minimized by choosing minerals to analyze that don't incorporate daughter particles when they form. For example, I work with zircon uranium-lead dating. When they form, zircons incorporate uranium into their crystal structure, but not lead, so it can be assumed that all lead in the zircon was produced by the decay of uranium. You can get inclusion of other minerals within zircons, which may contain lead, so before we do any analysis, we select zircons that are clear (not cloudy from mineral inclusions) and that don't have inherited cores from older zircons that were re-incorporated into the melt. This can easily be seen under a microscope, and ensures that the dates we get are as accurate as possible.

How do they know decay is a constant rate over billions of years?

Many different methods, all with different decay constants, are independently consistent with each other. If there was variation in the decay constants, no dating methods would agree. Moreover, they can be cross-verified against methods such as ice core dating and varves that do not rely on radioactive decay. These methods are consistent as well.

How do they know nothing has interfeared with the rate of decay over the billions of years?

See above.

2% accuracy still gets you into the tens of millions of years out, and I would like to know how they verify the acuracy? Sounds a bit sketchy to me.

In most cases, the accuracy is better than 2%, though it really depends on the method. For example, modern uranium-lead dating often has an uncertainty of less than 0.5%. In practice, not all numbers are perfect, which is why we include the uncertainty. It allows others to judge the validity of our data and conclusions.

Accuracy is verified several ways. Machine calibration is through standards (samples that have been run thousands of times or more by many different labs). We analyze several standards with each set of data and the variation from the accepted value gives us a correction factor for the new data we've collected. During analysis, we use standard error analysis methods (standard deviations, standard deviations of the mean, etc) to give us the uncertainty. These are then combined mathematically to give the final uncertainty of the value. This is the same method used in any other scientific measurement process.

 

[juvenissun]

There is no "radiation" in the rocks. You probably mean starting daughter isotopes. Isochron dating makes no assumptions about starting daughter isotopes and can be used to determine if there were any to begin with.


All evidence infers this, including examination of distant stars.


Only under extreme physical conditions is there any change in the decay rate.




The accuracy is determined by replication, and the technique used. Also, 2% error doesn't get you anywhere near to 6,000 years.



What sounds sketchy? You've barely looked at any details.

I thought IDers had no problem with Deep Time, since they weren't creationists (ha, ha).

No. It is not.

 

[sandwiches]

No. It is not.

I'm really hoping this is one of the mythical threads where Juve supposedly takes people to school or if this will fizzle out, yet again, with him saying about not wanting to do our work for us or that he doesn't want to teach us, after all.

 

[juvenissun]

As Split Rock said, there is no "radiation" in the rocks. What can throw off age calculations are excess daughter isotopes (decay products) that were not produced by the original parent isotopes in the rock. The effects of this are minimized by choosing minerals to analyze that don't incorporate daughter particles when they form. For example, I work with zircon uranium-lead dating. When they form, zircons incorporate uranium into their crystal structure, but not lead, so it can be assumed that all lead in the zircon was produced by the decay of uranium. You can get inclusion of other minerals within zircons, which may contain lead, so before we do any analysis, we select zircons that are clear (not cloudy from mineral inclusions) and that don't have inherited cores from older zircons that were re-incorporated into the melt. This can easily be seen under a microscope, and ensures that the dates we get are as accurate as possible.

Hey, brother. Be careful. There IS radiation in the rock.
"Don't put a pegmatite in your shirt pocket for long" is a joke. But it has some truth. Needless to say an U ore. (I gave my hot U-rich samples to physics department long time ago. It seems they don't mind but enjoy the clicking sound. But I do.)

 

[juvenissun]

How do scientists deside how much radiation was in the rocks to begin with, so they can decide percentage of rate of decay?

How do they know decay is a constant rate over billions of years?

How do they know nothing has interfeared with the rate of decay over the billions of years?


2% accuracy still gets you into the tens of millions of years out, and I would like to know how they verify the acuracy? Sounds a bit sketchy to me.

Well, I think you are asking the right questions.

 

[Split Rock]

Hey, brother. Be careful. There IS radiation in the rock.
"Don't put a pegmatite in your shirt pocket for long" is a joke. But it has some truth. Needless to say an U ore. (I gave my hot U-rich samples to physics department long time ago. It seems they don't mind but enjoy the clicking sound. But I do.)

There may be radioactive isotopes in the rock, but there isn't radiation sitting inside the rock like a mineral. Radiation may come out from the rock, but it doesn't reside in the rock.

 

[idscience]

There is no "radiation" in the rocks. You probably mean starting daughter isotopes. Isochron dating makes no assumptions about starting daughter isotopes and can be used to determine if there were any to begin with.


All evidence infers this, including examination of distant stars.


Only under extreme physical conditions is there any change in the decay rate.




The accuracy is determined by replication, and the technique used. Also, 2% error doesn't get you anywhere near to 6,000 years.



What sounds sketchy? You've barely looked at any details.

I thought IDers had no problem with Deep Time, since they weren't creationists (ha, ha).

I have no problem with deep time. I am just curious about dating methods as I have not studied them. The question was more inline with phylogenetic placements

 

[juvenissun]

There may be radioactive isotopes in the rock, but there isn't radiation sitting inside the rock like a mineral. Radiation may come out from the rock, but it doesn't reside in the rock.

My comment is indeed, not appropriate. But it is not because of your reason. I think I will be safe even I wear a big crystal of natural zircon on my finger.

 

[Myshkin99]

Here's a very good review of radiometric dating by a scientist, who happens to be a Christian, at Los Alamos National Laboratory. It is long, and it takes some effort to understand. The world is large and our brains are small. Don't let this deter you from exploring. It is a fascinating world.

This paper is available from the American Scientific Affiliation (A Network of Christians in the Sciences):

Radiometric Dating

 

[RickG]

How do scientists deside how much radiation was in the rocks to begin with, so they can decide percentage of rate of decay?

To begin with each radionuclide has its own rate of decay (half-life), no two are the same. The half-life depends upon the type of decay and its quantum make-up.

As for how much there is in the rock to begin with, it doesn't matter. It has nothing to do with how the age is determined. That determination is based upon the half-life of the parent isotope and the ratio of the parent to the daughter isotope. A basic formula is as follows:

D = D0 + N(t) (eλt − 1) where

t is age of the sample
D is number of atoms of the daughter isotope in the sample
D0 is number of atoms of the daughter isotope in the original composition
N is number of atoms of the parent isotope in the sample at time t (the present), given by N(t) = Noe-λt
andλ is the decay constant of the parent isotope, equal to the inverse of the radioactive half-life of the parent isotope times the natural logarithm of 2

The equation is most conveniently expressed in terms of the measured quantity N(t) rather than the constant initial value No.


The source for the above is from Wiki because it is probably one of the easiest understand for the layman. But for a more detailed source that gets more to the meat and potatoes.


http://www.science.smith.edu/geosciences/petrology/Notes/Equations_05.pdf

 

[dad]

.. Isochron dating makes no assumptions about starting daughter isotopes and can be used to determine if there were any to begin with. ...

False.


"All forms of isochron dating assume that the source of the rock or rocks contained unknown amounts of both radiogenic and non-radiogenic isotopes of the daughter element, along with some amount of the parent nuclide."


Isochron dating - Wikipedia, the free encyclopedia

"A radiogenic nuclide is a nuclide that is produced by a process of radioactive decay."

Radiogenic nuclide - Wikipedia, the free encyclopedia

So you see, this present state and decay are assumed. This is NOT known, and all dates are garbage until it is. God was right. Really.

 

[Split Rock]

False.


"All forms of isochron dating assume that the source of the rock or rocks contained unknown amounts of both radiogenic and non-radiogenic isotopes of the daughter element, along with some amount of the parent nuclide."

.

Wow. Do you even read what you quote here? What part of "Unknown" are you having trouble understanding?

 

[Anovah]

How do scientists deside how much radiation was in the rocks to begin with, so they can decide percentage of rate of decay?

Good question. Half life is only useful when you know the clock was set to zero.

My understanding is that when molten lava cools into igneous rock, crystals are created that favor potassium-40 %100 (i.e. there is none of the daughter isotope argon-40 present). From that point forward we only need measure the argon relative to potassium to determine the age.

How do they know decay is a constant rate over billions of years?

How do they know nothing has interfeared with the rate of decay over the billions of years?

Atomic theory is pretty well tested but scientists still cross reference their work with other natural clocks found on earth such as tree rings

2% accuracy still gets you into the tens of millions of years out, and I would like to know how they verify the accuracy? Sounds a bit sketchy to me.

It really comes down to half life. If you accept atomic theory and understand daughter isotopes and whatnot (which I am a layman at best), then there's really little left to argue.

I think that's why scientists get frustrated with creationism. It doesn't just address the big bang theory but it is in stark contrast with a whole heck of a lot of other science.