Radioisotope dating conveys an aura of reliability both to the general public and professional scientists. The best "proof" for millions of years of earth history in most people's minds is radioisotope dating. But is the method all it's cracked up to be? Can we really trust it? The lava dome at Mount St. Helens provides a rare opportunity for putting radioisotope dating to the test.
In August of 1993, I had the exciting privilege of accompanying geologist Dr. Steven Austin and others from the Institute for Creation Research on a climb into the crater of Mount St. Helens to view the lava dome. It was one of those experiences that was well worth every exhausting moment! The dome (Figure 1) sits like a small mountain (roughly 3/4 mile in length and 1000 feet high) directly over the volcanic vent, which is at the south end of the huge horseshoe-shaped crater blasted out of the mountain by the May 18, 1980 eruption. It is composed of a volcanic rock called dacite and appears to an observer in the crater as a huge steaming mound of dark, blocky rubble.
Actually the present lava dome at Mount St. Helens is the third dome to form since the 1980 eruption, the first two having been blasted away by subsequent eruptions. The current dome started to form after the volcano's last explosive eruption on October 17, 1980. During 17 so-called dome-building eruptions, from October 18, 1980 to October 26, 1986, thick pasty lava oozed out of the volcanic vent much like toothpaste from a tube. Dacite lava is too thick to flow very far, so it simply piled up around the vent forming the mountain-like dome, which now sits as a plug over the volcanic orifice.
Why does the lava dome provide an opportunity to test the accuracy of radioisotope dating? There are two reasons. First, radioisotope dating methods can be used mainly on volcanic (igneous) rock, such as dacite. (Fossil-bearing sedimentary rock cannot be directly dated radioisotopically.) Second, the date of formation of the dacite is known. (This is one of the rare instances in which, to the question, "Were you there?", we can answer-"Yes, we were!") It is widely assumed that the radioisotope clock is set at zero and starts ticking when igneous rock solidifies from a molten state.
The concept of radioisotopic dating is fairly simple. The method used at Mount St. Helens is called potassium-argon dating. It is based on the fact that potassium-40 (an isotope or "variety" of the element potassium) spontaneously "decays", becoming argon-40 (an isotope of the element argon). This process proceeds very slowly at a known rate, having a half-life for potassium-40 of 1.3 billion years. In other words, 1.0 gram of potassium-40, in 1.3 billion years, would decay to the point that only 0.5 gm was left. Theoretically, given certain assumptions, one could measure the amount of potassium-40 and argon-40 in a volcanic rock sample and calculate how old the rock is. When this is done, the age is usually very great, often millions of years.
In June of 1992, Dr. Austin collected a 15 lb. block of dacite from
high on the lava dome. A portion of this sample was crushed, sieved, and
processed into a whole rock powder as well as four mineral concentrates.
These were submitted for potassium-argon analysis to Geochron Laboratories
of Cambridge, MA, a high quality, professional radioisotope dating laboratory.
The only information provided to the laboratory was that the samples came
from dacite and that "low argon" should be expected. The laboratory was
not told that the specimen came from the lava dome at Mount St. Helens
and was only 10 years old. The results of this analysis, shown in Figure
2 (below), were recently published.1
|1. "Whole Rock"||0.35 ± 0.05|
|2. Feldspar, etc.||0.34 ± 0.06|
|3. Amphibole, etc.||0.9 ± 0.2|
|4. Pyroxene, etc.||1.7 ± 0.3|
|5. Pyroxene||2.8 ± 0.6|
What can one observe about these results? First and foremost is simply that they are wrong. A correct answer would have been "zero argon" indicating that the sample was too young to date by this method. Instead, the results ranged from 0.35-2.8 million years! Why is this? A good possibility is that solidification of magma does not reset the radioisotope clock to zero. Probably some argon-40 is incorporated from the start into newly formed minerals giving the "appearance" of great age. It should also be noted that there is poor correspondence between the different samples, each taken from the same rock.
Is this the only example where radioisotope dating has
failed to give correct dates for rocks of known age? Certainly not!
Dalrymple2 gives the following potassium-argon ages for historic
lava flows (Figure 3):
(in millions of years)
|Hualalai basalt (Hawaii, AD 1800-1801)||1.6 ± 0.16|
|Mt. Etna basalt (Sicily, AD 1792)||1.41 ± 0.08|
|Mt. Lassen plagioclase (California, AD 1915)||0.11 ± 0.3|
|Sunset Crater basalt (Arizona, AD 1064-1065)|| 0.27 ± 0.09
0.25 ± 0.15
Another example is found at the Grand Canyon in Arizona. The bottom layers of the canyon are widely held to be about one billion years old, according to evolutionary chronology. One of these layers is the Cardenas Basalt, an igneous rock amenable to radioisotope technology. When dated by the rubidium-strontium isochron method the Cardenas Basalt yielded an "age" of 1.07 billion years, which is in agreement with the evolutionary chronology.3
However, volcanoes of much more recent origin exist on Grand Canyon's north rim. Geologists agree that these volcanoes erupted only thousands of years ago, spilling lava into an already eroded Grand Canyon, even temporarily damming the Colorado River. Rocks from these lava flows have been dated by the same rubidium-strontium isochron method used to date the Cardenas Basalt, giving an "age" of 1.34 billion years.4 This result indicates that the top of the canyon is actually older than the bottom! Such an obviously incorrect and ridiculous "age" speaks eloquently of the great problems inherent in radioisotope dating. (Numerous other radioisotope "ages" are also given.)
Radioisotope dating is widely perceived to be the "gold standard" of dating methods and the "proof" for millions of years of earth history. But when the method is tested on rocks of known age it fails miserably. (The lava dome at Mount St. Helens is really not a million years old! We were there! We know!) By what twisted logic then are we compelled to accept radiometric dating results performed on rocks of unknown age? I would submit we are not so compelled, but rather called to question and challenge those who promote the faith of radioisotope dating.
"It is obvious that radiometric techniques may not be the absolute dating methods that they are claimed to be. Age estimates on a given geologic stratum by different radiometric methods are often quite different (sometimes by hundreds of millions of years). There is no absolutely reliable long-term radiological `clock'."6William D. Stansfield, Ph.D
1 Austin, S.A., 1996. Excess Argon Within Mineral Concentrates from the New Dacite Lava Dome at Mount St. Helens Volcano. CEN Tech.J., 10(3):335-343.
2 Dalrymple, G.B., 1969. 40Ar/36Ar analysis of historic lava flows. Earth and Planetary Science Letters, 6:47-55.
3 Austin, S.A.,(edit),1994. Grand Canyon: Monument to Catastrophe, Institute for Creation Research, Santee, CA, pp 111-131.
4 Austin, Ref. 3
5 Austin, Ref. 3 [not used in on-line version, at this time]
6 Stansfield, W.D., 1977. The Science of Evolution, Macmillan, New York, p 84.