Cavitation and the Flood

John Morris’ Acts & Facts article for this month is a little different from that of the last two months, in that it doesn’t resemble ‘filler’ quite so much. The piece is called simply Cavitation, and argues that the Grand Canyon could have been formed via this intriguing process.

Cavitation, as Wikipedia informs us,

…is the formation and then immediate implosion of cavities in a liquid – i.e. small liquid-free zones (“bubbles”) – that are the consequence of forces acting upon the liquid.It usually occurs when a liquid is subjected to rapid changes of pressure that cause the formation of cavities where the pressure is relatively low.

This is capable of eroding steel, and quite quickly at that. It can also cut through concrete and rock inside of dam spillways, as in the example of the 1983 flooding at the Glen Canyon Dam given by Morris:

The dam had been constructed to protect the Colorado River and Grand Canyon below from intermittent water floods. But spring runoff was threatening to overtop the dam and send enormous volumes of water downstream, possibly inflicting much damage to the dam and inhabitants below. To minimize the damage, the overflow spillways were opened, draining the excess water in a controlled fashion. Soon, clear lake water gushed from the tunnels as if from a giant hose.

On June 15, 1983, after four days of release, the lake level continued to rise, and flow through the spillway increased. All appeared to be going well, but seismographs sensed that something more substantial was happening underground. Suddenly, the exiting water turned muddy red—the color of the underlying rock—and huge chunks of rock and concrete were thrown out.

This event was credited to the process of cavitation.

Before they could close the spillway, water flowing at a rapid velocity had eaten through the spillway’s thick reinforced concrete casing and opened a huge chasm in the rock beneath. Within minutes, a cavern 32 by 40 by 150 feet had been excavated. Cavitation had eaten through the three-foot-thick, steel-reinforced concrete lining of the tunnel and into the underlying rock. It is possible that cavitation was pulverizing concrete, steel, and sandstone at a rate in excess of 1,000 cubic feet per minute during the peak period of erosion. Sixty-three thousand cubic feet of concrete was required to fill this enormous hole.

This sounds like a lot, but it actually isn’t. Sixty-three thousand cubic feet makes only 1784 cubic meters, which is just less than three quarters of the volume of an Olympic swimming pool. The rates given by Morris don’t seem to stack up, by the way: apparently the erosion took “minutes” (a solid with the given dimensions would be more than twice the volume of the concrete), yet even at the peak rate more than an hour would have been required. My research tells me that the volume of the Grand Canyon is 4.17 trillion cubic meters, so at the 1,000 cubic feet/minute rate it would take… a little over 280 thousand years. Of course, the erosion rate over the entire G.C would have been much higher, but that’s an awful lot of orders of magnitude to make up. Even at a constant rate sufficient to erode the full canyon in a year, a cube of rock 50 meters on a side would need to be shifted each second.

So I have my doubts that even this awe-inspiring process would be sufficient to erode the canyon within the timescales required. I remain unconvinced also, however, that cavitation would have occurred (at least at the necessary scale) at all. Then again, I’m no hydrodynamics expert, so I wouldn’t really know if it were feasible.

First, I draw your attention to this quote from a page giving information on the spillway:

The spillways are shaped somewhat like an arm with the cavitation damage occurring in the elbow area.

So the erosion didn’t happen all the way along the spillway, merely at an “elbow.” This raises questions of the processes’ applicability to the erosion of the Grand Canyon. Note also that the erosion happened in a tunnel, although cavitation can apparently take place in rivers.

Secondly, an article on Creation Ministries International’s website on this exact topic from 2007, quotes creationist and “cavitation expert” Dr Edmund Holroyd as saying in 1997:

When water less than 10 metres deep is flowing at very high speed (say 30 metres a second) and goes over a bump, it can turn into water vapor via the formation of tiny bubbles. These collapse again when the pressure is restored, and they do so at a supersonic speed which creates shock waves with incredible pressures. This pulverizes the surface right next to where the bubbles are collapsing, so it can “eat” rock surfaces away much, much more quickly than normal erosion. In the laboratory, such cavitating water will even rapidly “eat” a steel surface.

The ‘bump’ is a little more promising, but the “less than 10 meters” looks a bit unfortunate, given that the waters were apparently taller than mountains – and that the canyon is much more than 10 meters deep. So I don’t really know if it’s even remotely feasible or not.

Morris concludes his article like so:

Never again can we doubt that dynamic moving waters are capable of doing extensive geologic work in a hurry, even under “normal” conditions. We are still left to ponder the effects of the much more intense great Flood, which would have produced erosion on an even grander scale with waters flowing at much greater sustained volumes and velocities.

But here’s a question: why is this massive, world-spanning volume of water moving at such a rate? Where is it going? Wherever from? The Glen Canyon business had a sizable lake involved, providing energy to the water being shot through a small channel. I’ve heard of creationists proposing lakes forming the Grand Canyon, but a lake requires a rim all of the way around. I think Morris should give up on finding the ark, and concentrate on searching for the other end of the bathtub.

He might just find his rubber ducky in the process.