Lava Flows of Known Age, and Radiometric Dating

It has been shown many times that radiometric dating has a passel of difficulties. These include circular reasoning, presupposing deep time, unwarranted assumptions, and more. Samples tested by various methods provide wildly differing results, including lava rocks of known ages. Does the eruption make a difference?

Radiometric dating has numerous flaws. Tests of rocks with known ages give wildly differing results, and some people wonder if there is a kind of reset with lava.
Tungurahua eruption image credit: FreeDigitalPhotos / xura
This does seem like a reasonable question on the surface. I saw a comment at The Question Evolution Project about radiometric dating and lava of known ages. He figured that everything would be reset to zero, so old rock that became molten would appear young but is actually very old; a kind of reset. Arbitrary assumptions based on lack of knowledge raise more questions than they solve. Biblical creationists point out these flaws in uniformitarianism because the evidence indicates a young earth.
Once again, our feedback is about radioactive dating, which seems a major roadblock against Christians believing the world is the biblical age of 6,000 years. The basics are simple, but the process is complicated, and supporter Larry R wrote and asked about the issue.
I have a question about radiometric dating. I understand how the process works, and the various assumptions that go into it. My question is, would the age of the magma have any bearing on the age of the rock created from it?
Like, when Mt. St. Helen’s erupted in 1986, obviously we know when the rock was formed. If we were to send in various specimens for various testing, obviously the testing would indicate ages that are much larger than the actual age. My question is, do the isotopes (if any) in the lava/magma play a roll, and if so, how (or how not, if it doesn’t have any effect)?
Thank you for your time.
Larry R.
CMI’s geologist Dr Tasman Walker responded (edited for the web):
Hi Larry,
Thank you for your email and your question.
You said, “I understand how the process works, and the various assumptions that go into it.” I would not put it that way. I would say, “I understand how they say the process is supposed to have worked!”
To read the rest of the response, head on over to "Is radioactive dating affected by the age of the magma?"