November 13, 2006 | David F. Coppedge

How Not to Date a Volcano

Two teams of geologists looked at the same volcano field in Nevada. One (1994) decided that the cones and lava flows formed during multiple episodes over tens or even hundreds of thousands of years. Another (2006) looked at the same evidence and decided everything probably happened within months. Who’s right?

A team of six volcanologists from Los Alamos investigated Crater Flat, Nevada, and published their conclusions in GSA Bulletin.1 They think the earlier study was flawed. The way they see it, there was one eruptive episode that produced Red Cone, Black Cone and several others in the area, along with all their extensive lava flows. Just because lava flows look different, that doesn’t mean they happened at different times, they said; the differences could be due to varying initial conditions, like water content and thickness of the lava or degree of slope.

Three major surface features—scoria cones, lava fields with abundant rafts of pyroclastic material, and lava fields with little or no pyroclastic material—experienced different posteruptive surficial processes. Failure to account for the different initial surface features can lead to erroneous conclusions about the relative ages of the surfaces based upon modern morphology. Conversely, the recognition of different volcanic surfaces provides the opportunity to study the effects of different initial properties upon posteruptive geomorphic processes. Contrary to previous interpretations that the individual volcanoes were emplaced by polycyclic eruptions (separated by thousands or tens of thousands of years), we argue that the Pleistocene Crater Flat volcanoes are monogenetic, each having formed in a single eruptive episode lasting up to a few years. We show that all eruptive products emanated from the areas of the volcanoes’ main cones rather than from scattered vents, as inferred by previous workers.

Later in the paper, the authors said that the previous workers pointed to features that “would imply time gaps of many tens to hundreds of thousands of years.” By contrast, their scenario could have taken place in as little as nine months.

Observations that they feel misled the earlier team included apparent secondary vents emerging through the lava flows, and different amounts and types of erosion from one flow to another. Valentine et al now say that these were not secondary vents at all, but either remnants of the original cone that got rafted downslope by lava flows from the base, or were “squeeze-up ridges, roughly parallel to the flow margin, caused by pulses of lava behind a slowing flow front.” As for the erosional differences, these could be explained by the consistency of the lava, the effusion rate and the degree of slope. In other words, all the observations could be fit within a single eruptive episode lasting days, weeks, months, or a few years at most.

The authors believe these eruptions took place about a million years ago. This estimate, however, is based on magnetic data, not bulk appearance of the lava. They cherry-picked a date fitting the assumed potassium-argon (K-Ar) ballpark date into the nearest estimated period of magnetic reversal: “Flows of all of the volcanoes have reversed magnetic polarity, indicating that, if all the volcanoes are close to the same age, they are either older than 1.07 Ma or younger than 0.99 Ma (Fig. 2); for simplicity in this paper, we refer to the age of these volcanoes as ca. 1 Ma.” They did not question the dating of these magnetic reversals, however, which are subject to their own uncertainties.

How certain are the potassium-argon dates? “Six independent K-Ar and 40Ar/39Ar studies have been conducted since 1990 to determine the ages of these five volcanoes (Fig. 2), and the results are difficult to interpret,” they lamented. “Age estimates for any one volcano typically have uncertainties of 100-200 k.y. and a large range of individual age determinations, leaving a detailed understanding of the age relationships between volcanoes uncertain, as well as the possibility of a span of ages at individual volcanoes.” Their own research seems to illustrate the point.

Volcanoes are common features around the world. Many can be witnessed in action today, from the liquidy fire-fountains in Hawaii, to the explosive stratovolcanoes like Mt. St. Helens. One would think the common types of volcanoes found at Crater Flat are well understood and their eruptive and post-eruptive processes have been thoroughly documented. Not so; in their introduction, the authors complained,

Despite being one of the most common types of continental volcanoes and presenting hazards to urbanized areas, such as Mexico City (Siebe et al., 2004), and to the proposed Yucca Mountain radioactive waste repository (e.g., Crowe, 1986; Dartevelle and Valentine, 2005), the eruptive processes of small-volume basaltic volcanoes (composed of cones, lava flows, and fallout deposits with total volumes of ~1 km3 or less) have received relatively little attention in the volcanological literature. Much remains unknown about the ranges of explosive and effusive processes associated with their eruptions. The role of preexisting topography and the interaction between lava flows and cone building have not been explored in detail, nor has the influence of emplacement processes on posteruptive surficial processes.

1 Valentine et al, “Small-volume basaltic volcanoes: Eruptive products and processes, and posteruptive geomorphic evolution in Crater Flat (Pleistocene), southern Nevada,” GSA Bulletin, Volume 118, Issue 11 (November 2006), pp. 1313-1330.

Imagine you are a church-going high school student in Nevada in 1994, and your teacher takes your class out on a geology field trip to Crater Flat. Using information he just read in popular-science reviews of the 1994 paper, the teacher points out features of the lava flow, the cone, the amount and types of erosion – some gullies on the cone, rifts and rilles in the lava, slumping and overburden, mounds that look like secondary vents – to prove that there had been multiple episodes of eruption spanning tens of thousands of years – maybe even hundreds of thousands. He makes a convincing case. The evidence, after all, is right in front of you. It sure looks old. Some of the flows are highly degraded and overgrown with brush and sand, while others are fresh-looking and undisturbed. There are even younger-looking cones emerging from underneath the older lava.

Your doubts about the Biblical chronology grow in proportion to your increasing admiration for science’s ability to describe the history of the world in vivid detail. The onslaught against your faith is supplemented by what your biology teacher is showing the class about evolution. Over time, you find you have slid gradually into belief in scientism. You go to the university and become a hardened evolutionist. Church and youth group and your former acceptance of the Bible’s history become distant memories. You take part in school board hearings to fight even weak attempts to add scientific criticisms to Darwinism in public education. You read Dawkins’s latest book, The God Delusion with a snicker at those poor suckers who rely on “faith” instead of “science,” who still believe the Bible stories of creation and the Flood that were once a part of your own happy childhood. Parents should not deceive their children like that, you ponder with anger mixed with sadness, and a touch of nostalgia.

What is the likelihood that a little paper in GSA Today, appearing 12 years after your slide into atheism began, will cross your path? Its message, now unheeded, says, “whoops, we were wrong about those lava flows in Nevada; apparently they all formed within one year.” Even if you were to read it now, it’s probably too late. The furrow that began to be carved back then in high school has become a deep trench. You would probably brush this announcement off, even if you found it, with the thought that one paper doesn’t affect the mountains of evidence for evolution and millions of years.

This is one way lives can be diverted from Christian faith by lies and misdirection, well-meaning as some of the sources may be, because they did not understand the limitations of scientific epistemology. We’ve seen testimonies like this by evolutionary scientists who grew up in Christian homes. Charles Darwin himself provides a classic example. Reading Lyell on the Beagle, he witnessed South American canyons that were interpreted to take long ages, when in fact, they were the result of catastrophic events. Similar stories abound today. Whether through peer pressure, lack of contrary information or whatever, students began to trust the words of overconfident teachers who present science as the truth, instead of a fallible, human attempt to seek for the truth about the natural world.

For those still under the illusion that scientific knowledge is progressive, notice how this is a case of oscillation, not cumulative progress. An earlier (1981) study also concluded that the Crater Flat volcanic field was monogenetic, till the 1994 study overturned it. Now we’re back to the monogenetic story. No human can have any confidence that the story will not change again. If this were an isolated case, we might dismiss it as an anomaly. The authors told us, however, that these common types of volcanoes have received “relatively little attention” in the literature of the volcano experts, and that “much remains to be understood.” Those replying, “Well, at least we know the events took place a million years ago, not a few thousand,” haven’t gotten the message.

Observations do not interpret themselves. The authors used the words interpret or interpretation 22 times, including a few statements that the data are difficult to interpret and can be misinterpreted. That includes the K-Ar dates and the magnetic reversals. Cone-shaped structures looked like vents to the earlier group of scientists, but like squeeze-up ridges to the other. Eroded channels in the cone implied long ages to one group, but differences in composition to another. Smooth, fan-shaped lobate deposits implied millennia of erosion to one group, but effects of initial conditions to the other.

The potential for wide divergences of opinion in interpreting observations cannot be overemphasized. Almost every field of science has undergone a revolution since 1900. Even our concepts of atoms, the universe, the earth, and life are drastically different today than they were a century ago. We’ve seen many examples of radical reinterpretations of things in just the six years of Creation-Evolution Headlines. Does anyone believe that we have arrived at “the truth” about any of these fields, let alone the final word on these Nevada volcanoes?

There’s nothing about the Crater Flat observations that is inconsistent with the view that these volcanoes erupted quite recently, but were just not witnessed by humans (or humans who kept written records). Don’t build your epistemology on the sand of “what scientists are saying today.” Don’t trust your future to the religion of scientism, the faith that fallible humans are making progress toward understanding the origin and fate of the Earth, life and the universe.

For similar stories, see 10/25/2006 about Niagara Gorge, 10/15/2006 about instant gold, 08/08/2006 about ice cores, 05/10/2006 about Mt. St. Helens, 03/22/2006 about stromatolites, 03/05/2006 about Arizona lava flows, 06/27/2003 about ultra-pure sandstones, 07/22/2002 about Grand Canyon, and many more links on Geology and Dating Methods.

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