Rock Flows

When you compress rock – and by “you” I really mean vast tectonic forces, and not your literal thumb and forefinger – it will tend to deform in such a way as to reduce its size in the direction of force. There are two broad categories of deformation. In brittle deformation the rock breaks and moves along the resultant fault. The scale of this movement varies considerably: while not produced from compression, the Alpine Fault in the South Island displaces the rock on either side by hundreds of kilometres and presently moves at a rate of tens of millimetres a year, but these processes go as small as individual tiny fractures in a rock. While the scales might be impressive, brittle deformation is not all that alien to our experience – everyone knows that rock breaks.

At the other end of the spectrum is ductile deformation, including the process of folding. In this case, when compression is applied the rock layer gains waves like the folds in a rug. The scale of these folds can range from mountains down to individual crystals. But this latter kind of deformation is more than a little counter-intuitive: in our experience, rock generally doesn’t bend.

John D. Morris, the ICR’s president and holder of a PhD in geology, writes a regular geological column in his organisation’s Acts & Facts magazine. Several of those articles have recently exploited this potential for incredulity to put forward an explanation of the observed folding of rock that is more consistent with his creationist beliefs. While faulting can potentially happen in an instant, folding takes time – something which young Earth creationists famously lack.

But many of the sedimentary structures we see folded were originally lain down as pliable mud. “Soft-sediment deformation” is what we call deformation before rock has hardened, which does happen from time to time. In theory, this process could take place much faster, so Morris claims that all ductile deformation must be of this nature. That is to say, all folding of rock took place when it was still soft, and not when solid. In August, for example, he said:

Following Flood deposition of vast layers of sedimentary rock, the Alps were formed as Africa collided with Europe, rumpling the flat sediments into massive mountains. The sediments on the Matterhorn were still soft at the time of deformation, for they are tightly folded. It doesn’t take a long time for sediments to harden, given proper conditions. Those on the Matterhorn appear folded close together, not like hard rock that readily breaks when bent. The time between deposition and folding was perhaps just the months of violent tectonic activity during the Flood, not millions of years. Local high areas might have slid downward, resulting in a seeming reversed order. The Ice Age that followed the Flood covered much of Europe with moving glaciers that scoured the uplifted, and by then hardened, rocks into the majestic mountains we admire today.

For his October column he adapted part of a “technical article” he wrote on soft-sediment deformation with Steve Austin – apparently it “was awarded the best paper at the 1986 International Conference on Creationism” and “is just as relevant today for showing that Earth’s geology clearly supports the biblical record.” In this article he acknowledges that others have differing opinions, but scoffs at them:

[“Evoloutionists”] claim that, when deeply buried, rocks can slowly deform extensively. But there is a limit to how much solid rock, notoriously weak under tension, can bend without breaking. And the outer half of each layer would undergo tension at every single bend, leading to breakage. As illustrated in the accompanying sketch and photograph, although these layers were bent excessively, there is no evidence of broken cement grains. Instead, it appears the strata flowed as mud or deformed plastically. All of this leads to the better interpretation that the Split Mountain formation deformed while still soft in a bending “event” rather than slow “creep.” It is clear that the vast ages assigned to the strata are mere assumptions and that the uniformitarian interpretation of the deformation is incorrect.

By this point he has gone beyond simply insisting that he can also explain the observed folding, to solidly and repeatedly insisting that non-creationists cannot. In his November article, Ute Pass Fault: Sand Injectites And Rapid Deformation Fit the Flood (page 14-15 of the pdf, online article not yet available), he continues this crusade. Again insisting that all deformation must have occurred prior to lithification (i.e. when the rock was still soft), he points to the time gap between when the sediment at Ute Pass was lain down and when it was deformed:

The problem is that the strata involved are assigned an age of 300 million years while the folding event, the Laramide Orogeny, is regarded as taking place less than 70 million years ago. How could the material remain moldable for 230 million years?

Over these three articles Morris makes numerous claims – about flipped sediment at the Matterhorn, tightly folded sandstone layers at Split Mountain, layers folded by drag in contact with the Ute Pass fault, and others – but for the most part they stand and fall on the notion that solid rock cannot flow and fold. This may seem reasonable, at least based on human experience, but the forces involved here are so far beyond that reality has the potential to be very different.

Consider pitch, or bitumen. Bitumen may be technically a fluid at room temperature, but it’s a fluid that you can shatter with a hammer – not a result that you would expect. But a fluid it is still, and in 1927 Thomas Parnell of the University of Queensland in Australia began the famous “pitch drop experiment,” intending to demonstrate this paradoxical property to his students. Unfortunately for him there turns out to be a gap of nearly a decade between each individual drip in his setup, and it has only done so a handful of times since it’s creation. The next drop is imminent – though Parnell’s successor watching the experiment, John Mainstone, died recently having never managed to record or watch the event – while another version of the same experiment at Trinity College, Dublin was caught in the act on camera earlier this year:

Your everyday experience, therefore, cannot be relied upon to predict the properties of materials under many circumstances – even at room temperature and pressure over a mere human lifespan.

Returning to rocks, most of the folds we see pictures of are in sedimentary rock – rock that was once wet and muddy – which helps Morris promote his soft-sediment notion. But this is not the only kind of rock, and therefore not the only kind of rock that we see folded. Igneous intrusive rocks, like granite, are formed from solidifying magma underground and not mud on the surface and so present a potential problem for this idea. Unfortunately, while sedimentary rock forms natural layers that when folded are very visibly bent and twisted, in granite this can be less obvious. But one structure formed by igneous intrusions, dikes, has an appearance wherein folding can be very clear. Igneous dikes form when magma penetrates an existing rock through a crack, solidifying forming a sheet of igneous rock. When left alone and then exposed by erosion they produce features that often look like the picture above-right.

Now, courtesy of geologist Callan Bentley’s “Friday Fold” series, I have for you a folded granite dike:

© Callan Bentley, used with permission.

In this image, the darker rock is granite from “Virginia’s Blue Ridge basement complex.” This rock cooled and solidified from magma quite some time ago, although young Earth creationists often contend that basement rock was created as-is in the creation week. The light rock is also granite, of a different composition, and formed more recently when felsic magma penetrated the older rock producing a relatively linear structure that has since been folded as you see above. In the other pictures from Professor Bentley’s 2011 post – along with the higher-resolution version of the above composite image – you can see that in the middle of the fold where the Swiss army knife has been placed for scale the rock has developed a texture known as foliation, wherein the crystals of the rock reform to produce flat sheets that take up the least possible room in the direction of compression. The inescapable conclusion, whether you think this structure formed millions of years ago or on a windy Tuesday in late 1999, is that in this dike we have solid rock that has not merely been folded, but bent into a hairpin.

Closer inspection reveals that there are many fractures in this particular dike, but this is because ductile and brittle processes can and do occur at the same time. If this fold was formed purely through fractures and not real bending, the result would look more like the picture to the right. This is clearly not the case, however. Bentley has other examples of this phenomenon in his collection, including granite dikes that have been deformed so much that they boudinaged – sausage-shaped pieces broke away from the dike as if the solid rock was fluid. And it was, but not in the way you might have expected.

The notion that solid rock can deform considerably without breaking should really come as no surprise, if you properly consider the world around you. When rocks are forced past each other in faults they can catch against each other, causing energy to be built up and finally released in a potentially powerful and dangerous earthquake. But if rock could not deform, how would this energy be stored? It would be a very different world if it could not, but potentially a safer one.

Earthquakes are driven by tectonic processes – the convecting mantle is the source of the force that drives the continents into each other. But even though the mantle acts as a fluid over geological time, allowing convection to take place, it remains largely a solid. If it couldn’t move we would have no plate tectonics – and Morris would not have his “catastrophic plate tectonics” model for the Flood.

Solid rocks can bend – there is no better explanation of the evidence that leads us to this conclusion. And yet John Morris, an ostensible geologist, claims otherwise. I wonder what other nonsense could win “best paper” at a creationist convention?

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Thanks again to Callan Bentley for the picture – his blog, Mountain Beltway, really is a treasure trove.