Agnos1

Carbon dating can only be used on previously living organisms, not rocks.

Ask her why none of her "many many" scientists ever get published in legitimate scientific journals, or even National Geographic or the daily newspaper, for that matter.

ps418

Regarding the Global Flood and the Age of the Earth, you'll find all the ammo and info you need on my web site: <a href="http://www.geocities.com/earthhistory/" target="_blank">Creation Science and Earth History.</a> Otherwise you can invite you friend to the Evolution/Creation forum.

Patrick

ps418

Yes, and this is precisely the problem which the step-heating 40Ar/39Ar dating technique avoids. It is self-checking with regards to whether or not the system has remained closed. For an example of the precision and accuracy attainable with 40Ar/39Ar, check out:

P. R. Renne, W. D. Sharp, A. L. Deino, G. Orsi, and L. Civetta. 40Ar/39Ar Dating into the Historical Realm: Calibration Against Pliny the Younger. Science 1997 August 29; 277: 1279-1280.

Brent Dalrymple comments on the above paper, and on the subject of 'excess' age of recent lava flows:

Dating of The Mt Vesuvius Eruption

In the early afternoon of August 24, 79 CE, Mt Vesuvius erupted violently, sending hot ash flows speeding down its flanks. These flows buried and destroyed Pompeii and other nearby Roman cities. We know the exact day of this eruption because Pliny the Younger carefully recorded the event. In 1997 a team of scientists from the Berkeley Geochronology Center and the University of Naples decided to see if the 40Ar/39Ar method of radiometric dating could accurately measure the age of this very young (by geological standards) volcanic material. They separated sanidine crystals from a sample of one of the ash flows. Incremental heating experiments on 12 samples of sanidine yielded 46 data points that resulted in an isochron age of 1925 94 years. The actual age of the flow in 1997 was 1918 years. Is this just a coincidence? No — it is the result of extremely careful analyses using a technique that works.

This is not the only dating study to be done on an historic lava flow. Two extensive studies done more than 25 years ago involved analyzing the isotopic composition of argon in such flows to determine if the source of the argon was atmospheric, as must be assumed in K-Ar dating (Dalrymple 1969, 26 flows; Krummenacher 1970, 19 flows). Both studies detected, in a few of the flows, deviations from atmospheric isotopic composition, most often in the form of excess 40Ar. The majority of flows, however, had no detectable excess 40Ar and thus gave correct ages as expected. Of the handful of flows that did contain excess 40Ar, only a few did so in significant amounts. The 122 BCE flow from Mt Etna, for example, gave an erroneous age of 0.25 0.08 Ma. Note, however, that even an error of 0.25 Ma would be insignificant in a 20 Ma flow with equivalent potassium content. Austin (1996) has documented excess 40Ar in the 1986 dacite flow from Mount St Helens, but the amounts are insufficient to produce significant errors in all but the youngest rocks.

The 79 CE Mt Vesuvius flow, the dating of which is described above, also contained excess 40Ar. The 40Ar/39Ar isochron method used by the Berkeley scientists, however, does not require any assumptions about the composition of the argon trapped in the rock when it formed — it may be atmospheric or any other composition for that matter. Thus any potential error due to excess 40Ar was eliminated by the use of this technique, which was not available when the studies by Dalrymple (1969) and Krummenacher (1970) were done.

Thus the large majority of historic lava flows that have been studied either give correct ages, as expected, or have quantities of excess radiogenic 40Ar that would be insignificant in all but the youngest rocks. The 40Ar/39Ar technique, which is now used instead of K-Ar methods for most studies, has the capability of automatically detecting, and in many instances correcting for, the presence of excess 40Ar, should it be present.

<a href="http://www.ncseweb.org/resources/rncse_content/vol20/8906_radiometeric_dating_does_work_12_30_1899.asp" target="_blank">Radiometeric Dating Does Work! by G. Brent Dalrymple</a>

Patrick