Being a young-age creationist while you’re an undergraduate studying geology is a challenging experience. I remember it well. Many of the things I was being taught posed genuine questions for the biblical view of earth history, especially its short timescale, and often I didn’t have good answers.
During that time, I had to learn some important lessons: to hold on to God and his Word even in the face of perplexity, to be honest about the data and its challenges without being overwhelmed by it, and to seek new ways of understanding the world that were consistent with both the scientific data and biblical revelation.
Those lessons stood me in good stead. (In fact they’re helpful in the life of faith generally, not just in thinking about science). I needed to realize that it was okay to have unanswered questions. In fact, science is so much more fun because of all those unanswered questions! Of course, I’m also really interested to see how much light has been shed in the last couple of decades upon some of the things that bothered me as an undergraduate.
One of the problems I recall being particularly exercised about was the time needed for the formation of granite plutons. I was familiar with the conventional picture of how granites formed. From the generation of the magmas by partial melting of the lower crust, to their gradual ascent through the crust as balloon-shaped diapirs, their piecemeal assembly into batholiths with deep roots, their slow cooling dominated by conduction, and their eventual unroofing by erosion, they must have taken hundreds of thousands to millions of years to form. I just couldn’t see how it could be done within the time constraints imposed by biblical history.
Then came the granite revolution (Petford et al. 2000; Snelling 2008). Geologists began to call into question almost every aspect of this old view of granite formation. Granite magmas were no longer thought to ascend slowly through the crust as diapirs, but within days by dyke injection; the timescale for the filling of plutons was reduced to centuries or even months; batholiths were found to be mostly tabular structures, without deep roots, thus reducing the time needed for their cooling; a greater role for convection also served to lower estimated cooling times; phreatic stripping and other processes suggested that unroofing could occur rapidly. Even the generation of the magmas by partial melting was now thought to take only years to decades.
Furthermore, research on the formation of isolated polonium radiohalos within biotite flakes in granite plutons began to suggest even tighter constraints on their cooling history. The hydrothermal fluid transport model proposed by Snelling (2005) indicates that very short-lived polonium isotopes were separated from their parent uranium source and transported short distances by hydrothermal fluids where they became concentrated into new radiocentres. However, the requirement for an abundant supply of polonium and the fact that halos could only be preserved once the temperature of the host mineral had fallen below 150°C (their annealing temperature), implied a startlingly short timescale of formation of only hours to days. Incidentally, predictions based on this hydrothermal fluid transport model have recently been confirmed by data collected from a nested suite of granite plutons in Yosemite National Park (Snelling and Gates 2009).
The point is that the problem of granite formation, which so troubled me as an undergraduate, no longer seems quite so insurmountable. Of course, that hasn’t happened in every case. Other problems haven’t been resolved yet. Some even seem greater today than they did back then. But the revolution in thinking about granites gives me encouragement to think that answers to these other problems might be forthcoming one day too. I may or may not be around to see them, but that’s okay. In the meantime, I’ve learned to live with the uncertainty.
Petford N., Cruden A. R., McCaffrey K. J. W. and Vigneresse J.-L. 2000. Granite magma formation, transport and emplacement in the Earth’s crust. Nature 408:669-673.
Snelling A. A. 2005. Radiohalos in granites: evidence for accelerated nuclear decay. In: Vardiman L., Snelling A. A. and Chaffin E. F. (editors). Radioisotopes and the Age of the Earth: Results of a Young-Earth Creationist Research Initiative, Institute for Creation Research, El Cajon, California and Creation Research Society, Chino Valley, Arizona, pp.101-207.
Snelling A. A. 2008. Catastrophic granite formation: rapid melting of source rocks, and rapid magma intrusion and cooling. Answers Research Journal 1:11-25.
Snelling A. A. and Gates D. 2009. Implications of polonium radiohalos in nested plutons of the Tuolumne Intrusive Suite, Yosemite, California. Answers Research Journal 2:53-77.