Subscribe now


More in this category:

‘Ages’ obtained for the lava dome of Mt St Helens

May 2005 | by A. J. Monty White

Many creationists believe the earth was created by almighty God some thousands of years ago. Evolutionists, on the other hand, maintain that the earth is about 4.6 billion years old. How can there be such a vast discrepancy between these dates?

Many Christians find this a real problem for they think that the evolutionary scientists cannot possibly be wrong. Surely, the evolutionists’ dating methods cannot be that inaccurate?

But they can. The ‘ages’ obtained by radiometric dating for the rocks from the third lava dome on Mount St Helens — unquestionably formed since the May 1980 eruption — demonstrate the serious unreliability of radiometric dating.

The third dome

The rock that made up the third lava dome on Mount St Helens is dacite— a fine-grained volcanic rock that contains a sprinkling of larger visible crystals, like currants in a fruit cake.


Dacite lava is too viscous to flow very far and so it just piles up around the vent of the volcano and forms a hill-like dome plugging the volcano. This dacite lava contains the element potassium and (since potassium contains a radioactive isotope) can be subjected to potassium-argon radiometric dating.

This provides a unique opportunity to test the accuracy of this commonly used method of dating rocks, because we know exactly when this volcanic rock was formed. We really can answer ‘Yes!’ to the question, ‘Was anyone there when this rock formed?’

No speculation or guesswork is needed, based on the supposed ages of particular fossils or superimposed sedimentary rock.

Potassium-argon dating

Potassium-argon dating is used by geologists to determine the ages of igneous rocks (rocks solidified from a molten state). So this method can be used to date volcanic rocks, such as the dacite lava dome on Mount St Helens.

Potassium-argon dating works like this: Potassium-40 (an isotope or variety of potassium) spontaneously decays into argon-40 (an isotope of the element argon). This decay is very slow — so slow that it has a half-life of 1,300 million years (the half-life is the time taken for half the radioactive potassium isotope to decay to argon).

When a volcanic rock is molten, it should contain no argon-40 since it is ‘boiled out’ at such high temperatures. Hence by measuring the amounts of potassium-40 and argon-40 in a volcanic rock, it should be possible to determine the age at which the rock solidified — because the rate at which potassium-40 decays into argon-40 is known.

Too small to measure

Because the half-life of potassium is so long, lava solidified less than 25 years ago should contain so little argon-40 that it is ‘too small to measure’. Consequently, any age determination using the potassium-argon method of dating should give the age of the rock as ‘too young to measure’.

Samples of the dacite lava from the dome that formed between 1980 and 1986 were collectedin June 1992 and were sent for dating analysis at Geochron Laboratories of Cambridge, Massachusetts.1 The laboratory was not told where the samples came from — simply that they were from a dacite lava and that low argon was expected.

The results from the laboratory were staggering. The ages obtained by potassium-argon dating ranged from 340,000 years up to 2.8 million years (see Table). Yet the rock was only a dozen years old!

Wrong assumptions

What can we learn from this? Firstly, that the assumptions made in radiometric dating may be spectacularly wrong. It is assumed that there is no ‘daughter element’ (in this case argon-40) in the rock when it solidified. Clearly, this lava from Mount St Helens

didcontain some argon-40 before it solidified, thus giving it a false appearance of age.

We cannot here go into all the different radiometric methods used to date rocks, and the reader is referred elsewhere for a detailed discussion. What we can say, however, is that

allradiometric dating methods involve someunproven assumptions — even the ‘isochron’ methods that are often claimed to eliminate such assumptions.

The false ages obtained by radiometric dating for the dacite lava from Mount St Helens call into question the accuracy of the whole radiometric dating approach. If the ages obtained by such methods are wildly inaccurate for rocks of a known age, how can we trust them for rocks of an unknown age? We cannot!

Geologists are well aware of these problems, of course, and often ‘check’ their radiometric dates against the accepted ages of sedimentary rocks in the ‘geological column’.

But these sedimentary ages (established long before radiometric dating was available) are also based on assumptions — namely, that extremely low rates of sedimentation have predominated throughout the history of the earth. As the article on page 16 shows, such assumptions can also be wildly wrong.


At the beginning of the article I posed the question how there can be such a wide difference between the figures proposed for the age of the earth by evolutionists and young-earth creationists.

The data from the potassium-argon dating of the dacite lava from Mount St Helens should help us understand — the age of the earth determined by radiometric dating may be wildly inaccurate and cannot be trusted. There is no convincing evidence that the earth is billions of years old.

By contrast, the Word of God can be trusted when it points to a recent creation. God was there when he created and he has revealed this to us in the pages of Scripture.



2. Austin, S. A. Excess argon within mineral concentrates from the new dacite lava dome at Mount St Helens volcano,

CEN Tech. J. 10[3] (1996) pp. 335-343.

A. J. Monty White BSc, PhD, CChem, MRSC is a chemistry graduate who also studied geology at university. Following a career in university administration at Cardiff University, Monty joined Answers in Genesis (UK/Europe) as Chief Executive in 2000.