NetDoc,
Yes i am sure it was ten years old - it was a lava dome sample from Mount Saint Helen's 1980-86 erruptions.
But you find a problem with ONE method of dating and dismiss ALL of them? Typical knee jerk reaction of an extremist.
Yours is the knee jerk reaction - i haven't even commented on the other dating methods yet.
You've just defeated your own point then - if it wasn't lava, then it quite clearly has been a while since the matter of that rock was molten the last time. MSH merely ejected it to the surface.
It was lava at one stage - during mount saint Helen's 1980-1986 erruptions - it was a lava dome sample. It was rock - not lava when it was measured.
Furthermore, due to the slow decay of potassium, it cannot be used on ten years old samples anyway, it's absolute error margin is too large for that.
It's not the error margin - there shouldn't have been any Argon present in a 10 year old sample according to the assumptions used to date rocks of unknown age. The sample should have come back with the 'no Argon present' tag - it didn't. Hence the vast ages were not correct.
Saying that because of a failure of Pt/A dating to come up with a good age for something supposedly ten years old it cannot be used for older things is like saying that because yardsticks don't give good results for the width of a bacteria they cannot be used to measure the length of your room.
So you see, it has nothing to do with the large margin of error whatsoever.
And exactly that can be checked with isochron dating.
Yes, and yet it is not foolproof. There are known processes which invalidate this and we have to assume that these have not occurred. Let me provide another example for you:
The Grand canyon - 27 samples taken from the same geologic formation, using the Potassium-Argon (K-Ar) the dates varied from 400 +- 10 million years to 2600 +- 75 million years.
Now 7 samples where taken from the same lava flow - so they should have been all the same date. The K-Ar dates varied from 1050 to 2600 million years. Now two of the samples were taken 80cm apart from one another, the date of one was
1200 million years and the date of the other was
2600 million years! Now it doesn't take a genius to work out that if the argon concentrations can differ that much between a metre then you haven't a hope of figuring out what the original concentrations where since the original concentrations must have varied wildly across the lava flow.
Now three other dating methods were used with the isochron plots. Rubidium-strontium (Rb-Sr), samarium-neodymium (Sm-Nd) and lead-lead (Pb-Pb).
The ages for the rock were calculated as follows:
Rb-Sr = 1240+-84 Million years
Sm-Nd = 1655+- 10 Million years
Pb-Pb = 1883+-53 Million years
Each of those ages is vastly different from the other - they are statistically different.
There should be no difference if isochron are able to predict the amounts of daughter isotopes present in the rock in the first place. In reality the use of isochrons themselves are based on assumptions just like the K-Ar dating method - this is the reason why the dates are so far out between themselves and also between the different dating methods. It is not reliable.