A young-Earth creationist magmatic model for the origin of evaporites
On my most recent “Around the web” post, I stated that I would be writing a longer response to the young-Earth creationist (YEC) proposal that salt deposits (usually referred to as evaporites) were actually formed through igneous processes rather than being precipitated from seawater. This may not be that longer response. Instead, it is a quick review of Stef Heerema’s article published in the Journal of Creation in 2009 (A magmatic model for the origin of large salt formations) and his more recent You Tube video defending and expanding on this hypothesis. What is really needed is a comprehensive overview of the formation of evaporites in the context of the young-Earth/old-Earth debate, and as I said, this is not it.
This proposal was brought to my attention when I read an endorsement of it from YEC geologist Tas Walker. On his BiblicalGeology blog, Walker wrote:
[Heerema’s] research shows that the salt pillars around the world are elegantly explained by the interaction of a melted salt magma with the waters of the worldwide Flood.
I like Stef’s model, and think it is far superior to the uniformitarian attempt to explain the evidence, which I was taught at university in my geology course. That model hypothesizes that hundreds of kilometres of seawater evaporated slowly in an enormous, shallow, secluded area of the coast, over millions of years.
Before I go through the article, I need to comment about what drives Heerema’s igneous model, which is the perceived necessity to fit the geological record into what he calls “the biblical timescale.” It would be much better to refer to this as “the YEC timescale,” because that is what it is; it is not the biblical timescale. The Bible nowhere says that the geological record—virtually all the sedimentary, igneous, and metamorphic rocks dated Late Precambrian and later—was formed by Noah’s flood. The “necessity” to squeeze a billion years of Earth history into Noah’s flood is something YECs impose on the text of Genesis, and there are plenty of theologically conservative biblical scholars who disagree with this.
Evaporite minerals include halite (NaCl, rock salt), gypsum (CaSO4•2H2O), anhydrite (CaSO4), sylvite (KCl), and a host of other minerals. The term “evaporite” is not neutral; it implies that the rock was formed by a process that involved evaporation of water. In standard geological models, seawater is isolated from the main body of the ocean in a basin where evaporation leads to precipitation of these minerals. I will stick with the term because it is the common name for these rocks, and because I believe it is an accurate term in most cases.
Heerema’s paper is divided into four sections: Salt formations worldwide, Igneous origin of salt formations, Diagenesis of salt after original deposition, and a conclusion. The entire paper is three pages long.
First section: Salt formations worldwide
In the first section, Heerema describes the worldwide distribution and origin of salt formations. He then attempts to explain why old-Earth models are inadequate for explaining the existence of evaporites. He gives a very brief and incomplete summary of evaporite models used by geologists, then gives what he thinks are four reasons to reject these models:
- “To form a deposit only 1 km thick would require seawater 60 km deep to be evaporated.” — Seawater evaporation rates in tropical areas are on the order of one meter per year. One meter of seawater, if evaporated completely, would leave behind 1.5 cm of evaporite minerals, mainly halite (NaCl). At a rate of 1.5 cm per year, it would take 67,000 years to accumulate 1000 meters of salt, which is a short amount of time geologically speaking. That does not mean that evaporite minerals actually accumulated that quickly; there would have been many other factors involved, including the rate of subsidence of the depositional basin.
- “The salt formations show negligible contamination with sand, contradicting the evaporation model which requires a sandbank in combination with consistently dry weather over a long period of time.” — This is a misrepresentation or misunderstanding of geological models for evaporite formation in marine environments. A common feature of these models is the need for a barrier (often referred to as a “sill”) that restricts movement of seawater into an enclosed basin where evaporation of the seawater can occur, leading to precipitation of various evaporite minerals. Complete evaporation is not necessary. The barrier could be sandy, but that sort of sill would be susceptible to erosion. More likely the barrier would be consolidated or semi-consolidated. Reefs or other biological mounds would work very well for this, and some ancient evaporite deposits grade laterally into reef deposits.
- “The salt formations exhibit negligible contamination with marine fossils” — Most marine organisms do not thrive in hypersaline environments—think of the Dead Sea or Great Salt Lake—so it is unclear why Heerema would expect us to find abundant fossils. One type of fossil that is found in some evaporite deposits is pollen. It makes a lot more sense to posit that pollen was carried to the basin by the wind, than to suppose that a salt lava flow under Noah’s flood somehow absorbed pollen grains from flood waters without metamorphosing them.
- “The evaporation areas need to be in regions of high sunlight and low rainfall if the seawater is to evaporate. However, the distribution of salt deposits globally contradicts the idea that all of these areas were once near the equator for the required time to achieve such a result.” — First, Heerema assumes that deposits that are now far from tropical areas were far from tropical areas when they formed. Contrary to this, there is good evidence that the equator ran through North America during the middle of the Paleozoic. Other parts of the world that are now polar or temperate were also once much closer to the equator. Second, Heerema assumes that climate patterns have been similar throughout Earth history. He is applying a Quaternary (ice age) picture of the world to times in the past that were probably much warmer, even at high latitudes.
Second section: Igneous origin of salt formations
This section began with a quote from James Hutton’s Theory of the Earth back in 1788:
“It is in vain to look, in the operations of solution and evaporation, for that which nothing but perfect fluidity of fusion can explain.”
Hutton may not have been able to envision how contorted layers could form in evaporites, but in the two hundred years since we have made a little bit of progress in the Earth sciences. There is plenty of laboratory and field evidence that salt can flow—in the solid state!—in amazing ways, whether in the subsurface or on the surface as salt glaciers in places like Iran.
Heerema lists six evidences for the igneous origin of evaporites:
- “The temperature required to melt salt and create a salt “magma” are well within the range of magmatic temperatures for silica [sic] magmas.” — However, there is no evidence that something like a salt magma has ever existed in the Earth. Contacts between evaporite formations and other rocks show no signs of contact metamorphism (alterations to minerals caused by heat and hot fluids). Some evaporite minerals, such as carnallite and bischofite, can form by precipitation from seawater, but cannot form from a salt melt.
- “Molten NaCl flows easily like water.” — What Heerema does not demonstrate is that an NaCl lava flow could spread out underwater over many tens of thousands of square kilometers, which is what he is proposing. Heerema claims that calcite and anhydrite could form when water boils in contact with a salt magma, but does not state how this would happen or give any references.
- “It is well known that silica [sic] magmas can produce layered igneous intrusions. Likewise, the crystallization and cooling of the salt “magma” after emplacement will cause segregation of the different salts into layers within the core of the deposit, as found in the formations.” — This paragraph was very confusing. It is not clear whether he was advocating a salt lava flow extruding onto the ocean floor beneath the waters of Noah’s flood, or a salt magma intruding into already existing sediments. In addition, layering of different evaporite minerals generally follows the order of precipitation from solution rather than the order of crystallization from a melt, though there are many exceptions.
- “The Great Rift Valley is a 6,000-km-long geographic trough formed as the result of a parting of the continental crust from northern Syria in southwest Asia through the Dead Sea and the Red Sea into central Mozambique in East Africa… Given the location of these massifs it seems obvious that these have a volcanic origin.” — No. What is common about evaporites along the rifts of of Southwest Asia and East Africa is that they are in basins caused when blocks of Earth’s crust sink as the crust is being pulled apart. Thick evaporite layers occur in locations where there is rifting, a hot, dry climate, and restricted connection to the sea, like the Dead Sea and Danakil Depression. This is precisely what old-Earth geological models for evaporite formation propose. There is no direct association between evaporites and volcanic areas. Many evaporite deposits occur in areas with no volcanic rocks at all.
- “For a modern analogy of magmatic salt formation we can look at the Ol Doinyo Lengay volcano in the north of Tanzania within the Great Rift Valley.” — The only analogies between carbonatite volcanism and Heerema’s proposed salt magma are that carbonatite lavas have a low viscosity and some carbonatite rocks are rich in sodium (Carbonatites are rare igneous rocks based on the carbonate ion, CO32-, rather than on SiO2). Oldoinyo Lengai (Earth’s only known active carbonatite volcano) is in no more a modern analogy for salt magmas than the fluids in a vinegar and baking soda “volcano” would be.
- “Organisms and vegetation deposited in the valleys (or under the water) that are overrun by the flow of salt magma will, in the absence of oxygen, be transformed into coal, oil and gas…. The magmatic origin of these salt formations explains the connection between the salt deposits found around the globe and the associated coal, oil and gas reserves.” — There is no association between the occurrence of evaporites and coal. Coal deposits are usually terrestrial, and most large evaporite deposits are in shallow marine sequences. Hydrocarbon reservoirs are more often associated with evaporite deposits, but the presence of evaporites are not required for the transformation of organic material into oil and gas. The association is more of a coincidence; oil and gas form in marine sedimentary basins, and evaporites also form in marine sedimentary basins.
Third section: Diagenesis of salt after original deposition
In this brief section, Heerema writes about post-depositional changes (diagenesis) affecting salt. These changes include intense deformation that is present in most rock salt formations. However, he did not relate this to his igneous evaporite model.
He also mentioned the existence of salt hot springs in the Danakil Depression of Eritrea. Again, I am not sure how this related to his model. One would expect hot water percolating from the ground after transiting thousands of meters of salt to be salty. This brine is not coming from the mantle or deep in Earth’s crust; it is coming from within the basin itself, so is completely irrelevant to the model.
A few additional observations
Most large evaporite deposits are associated with shallow marine sedimentary rocks—limestones, sandstones, and shales that contain marine fossils—which is further evidence that these precipitated from seawater rather than having been formed by igneous processes.
If salt magmas were rising from Earth’s crust beneath a sedimentary basin, one would expect there to be hydrothermal alteration of the country rocks (the rocks the magma was moving through). Hydrothermal solutions are mineral-rich hot water solutions associated with igneous and metamorphic processes, and are the source of veins in rocks, such as the quartz veins that can contain gold deposits. I would not expect gold-containing solutions, but I would expect some sort of hydrothermal activity.
Heerema provided no evidence for feeder dikes—the conduits through which the supposed salt magma erupted.
Fluid inclusion studies indicate that evaporites formed from seawater. Fluid inclusions are tiny bubbles that contain remnants of the original fluid. Young and Stearley, in their discussion of evaporites, refer to a paper in which the composition of the brine in Silurian salt in the Midwest was consistent with a marine origin, and the researchers determined that the fluid inclusion must have formed at a temperature between 2° and 25°C, which is far below the melting point of NaCl.
Heerema focused on halite (NaCl), but made only passing references to anhydrite (CaSO4), and did not mention gypsum (CaSO4•2H2O) at all. In some evaporite deposits, anhydrite and gypsum dominate over halite. He also did not mention terrestrial evaporites, such as those found in the lake deposits of the Green River Formation.
Peer Review in the YEC technical journals
The home page of the Journal of Creation states that the journal is peer reviewed. Peer review is an essential component of the process of publication of research results, and has many benefits both for the author(s) and the scientific community as a whole. A paper can, in some cases, be submitted to a journal, reviewed, and be sent back to the author several times before it is published, a process that can take over a year. Not only does this process lead to a much better report, but it weeds out some papers that are not suitable for publication.
The publication of a paper such as this demonstrates that the Journal of Creation does not do an adequate job of putting geological papers through the peer review process. In saying this, I am not referring to the implausibility of Heerema’s igneous origin for evaporites, but the little things in the article that a good geological editor or peer reviewer should have noticed:
- Minerals do not evaporate from seawater, they precipitate.
- One of the substances listed as an evaporite mineral is magnesium chloride (MgCl2). Magnesium chloride does not exist as MgCl2 in evaporites, though its hydrated form (bischofite, MgCl2•6H2O) does occur.
- Evaporation leading to evaporite mineral formation is not greatest at the equator, but in the desert belts 10° to 40° north and south of the equator.
- Heerema does not properly distinguish between a magma, which would be within the crust, and a lava, which is extruded onto the surface. For example, he states that “a salt magma will flood into the lowest areas.” For this reason, the first time through the article I was not sure whether he was proposing instrusion of salt magma—a salt batholith—or salt lava flows, especially since in one place he refers to layered igneous intrusions.
- There are two references to silica magma when he meant silicate magma. A silica magma implies molten SiO2 (a magma that does not exist in nature), whereas a silicate magma contains many ions (iron, magnesium, calcium, potassium, sodium, aluminum, and many others) and dissolved gases in a silicate ion (SiO44-) melt.
I do not primarily blame the author for these errors but the Journal of Creation for letting them slip through. A valid peer review and editing process would have eliminated these sorts of errors.
This has always been a problem in YEC technical literature. Back in my YEC days, when I was a student member of the Creation Research Society, I remember cringing at some of the stuff that got printed in what was then considered to be the premier YEC scientific journal, the CRS Quarterly.
The YouTube video
I will not present a detailed analysis of this video, but do want to make a few comments:
- 4:15 — A hydrothermal origin for salt formations was briefly discussed, but this would only deposit evaporite minerals within pre-existing rocks, not in large, separate evaporite layers.
- 8:20 — “Carbonatite” was listed as an evaporite mineral. Carbonatite rocks are formed from carbonate magmas, and have a very distinctive mix of minerals. There is little overlap between the lists of minerals found in evaporites and carbonatites. One exception is calcite (CaCO3), which is formed in a very wide range of geological settings.
- 10:30 — There was a presentation of a NaCl-CaSO4 phase diagram, which he got basically correct in terms of which mineral would crystallize first. But the final crystallization would produce an interlocking mesh of halite and anhydrite, not segregated layers of the two.
- 12:45 — Here the discussion of salt pillars (salt domes, diapirs) begins. Heerema proposes that these salt pillars, which can rise through thousands of meters of sediments, formed while the salt was molten beneath flood waters. The salt developed a crust, but this crust would crack at times, creating upward convection currents of steam. The molten salt would rise up in the steam and water column to form a salt pillar thousands of meters tall. He showed a video of a transparent tank containing a layer of molten NaCl beneath water. The two were separated by a barrier simulating the solid salt crust. Then he exposed the water to the molten salt, which led to the formation of steam. What would have been really impressive would have been a time-lapse movie of a solid salt pillar forming in his tank, but he did not do that.
- 19:20 — Heerema discussed how the upturned sediments around these “salt pillars” could easily have been formed by deposition from fast moving water currents circulating around the salt pillars, but are impossible to explain by standard geological theories. This was the typical YEC “only explainable by catastrophe” tactic. What he missed is that upturned sedimentary layers next to salt domes show every indication of having been deposited horizontally, and then punctured by rising solid but moldable masses of salt. These layers show the typical signs of strain associated with deformation, including folding, fracturing and faulting.
The proposal that evaporite formations were formed by primary igneous processes is not a step forward for YEC flood geology. The hypothesis has little evidence to support it in terms of global distribution, relationship of evaporites to surrounding rocks, or known geological processes. The publication of this paper demonstrates that there are serious problems with the YEC peer review process.
I want to state again that none of this is biblically necessary. The Bible is not a book about the origin of evaporites, or any other sedimentary rock. This sort of “research” discredits the Bible and Christianity, which is both tragic and unnecessary.
Any upper-division undergraduate textbook on sedimentary petrology will have a good discussion of the characteristics, distribution, and origin of evaporites. This week, I read the section in Principles of Sedimentology and Stratigraphy by Boggs, which I am reading this spring just for fun. The fifth edition is listed on Amazon for $146. I bought it new in South Korea two years ago for only $42. College textbooks are such a scam.
Carbonatites are fascinating igneous rocks. Again, any good upper-level undergraduate or graduate textbook on igneous petrology will have a discussion about these. For some good pictures of Oldoinyo Lengai in action, click here (National Geographic) or here.
I am not saying that salt magmas are impossible. I am saying that there is no good support to Heerema’s hypothesis.
The fluid inclusion study on Silurian evaporites was discussed in Young and Stearley, The Bible, Rocks and Time, pp.303-304.
I got a few of the ideas presented here from a comment by steve660 (the comment on Sat Mar 16, 2013 8:13 pm) on the British Centre for Science Education web site. He recognized problems with the stability of magnesium salts at high temperatures that I did not catch.
Grace and Peace
In a way, I really do not enjoy writing something like this. Young-Earth creationists are my dear brothers and sisters in Christ.