Greene's Creationism Truth Filter

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Cooling Magmas: More Distortions from
Snelling and Woodmorappe

by Kevin R. Henke, Ph.D.

One of the countless problems for young-Earth creationism (YEC) is how plutons can form and cool within the maximum YEC time frame of only a few thousand years. While YECs Snelling and Woodmorappe (1998) attempt to deal with some aspects of this issue, a careful reading of their manuscript shows that they blatantly ignore many problems that refute their extreme brand of creationism.

Traditionally, granitic plutons have been viewed as bulbous diapirs of molten rock rising through the crust. Strahler (1987, p. 213) cites probably outdated calculations from Ramberg (1963) and argues that such diapirs would take about 150,000 years to rise from their sources to the upper crust. Of course, 150,000 years is too long for Snelling and Woodmorappe (1998, p. 527), who argue that the Earth is only 6,000 to 7,000 years old. In recent years, however, geologists have been abandoning the idea of diapir emplacement of igneous rocks, especially in the upper and middle crust (Pitcher, 1997, p. 220-221). Calculations in Clemens and Mawer (1992) show that slow diapirs would solidify before they could reach the upper crust. Many geologists now believe that granitic plutons develop as blobs that resemble expanding balloons or form quite quickly from feeder dikes (Pitcher, 1997, p. 193-195, 219-221; Clemens, 1998). Not surprisingly, young-Earth creationists (YECs) wholeheartedly endorse feeder dikes, since feeder dikes may emplace fairly large granitic plutons in only a few thousand years. Snelling and Woodmorappe (1998, p. 528) even quote Pitcher (1993, p. 186), which states that the growth of granitic plutons by dike injection along fractures may be very fast:

"... what is particularly radical is their [Clemens and Mawer, 1992] calculation that a sizable pluton may be filled in about 900 years. This is really speedy!"

In the 1997 edition of Pitcher's book (p. 220), however, he revises his wording and clearly expresses skepticism about the span of 900 years:

"The calculations of Clemens and Mawer, referred to at length earlier in this book, show that the times needed for a thick dyke [American spelling: dike] to fill a pluton are 'impressively brief,' and since a sizable pluton might be fed by a number of such dykes this would be an efficient method of rapidly transporting magma and building batholiths; one of Clemens and Mawer's estimates is just 900 years. This is really speedy and I choose to remain skeptical of such rapid rates of ascent of silicic magma."

Later, Pitcher (1997, p. 221) concludes that the emplacement of granitic magma by feeder dikes could occur within a few thousand years. The rapid movement of magma through kilometers of crust is not a new concept. For example, Hyndman (1985, p. 132) quotes Eaton (1962), which states that prior to its eruption from an Hawaiian volcano, earthquake foci were used to follow the movement of magma over two months through about 60 kilometers of crust.

Although magmatic diapirs have been strongly criticized in recent years, Weinberg and Podladchikov (1994) have shown that magma diapirs may reach the middle or upper crust before solidification if the diapirs rise through a "thermally graded power law crust." Under such crustal conditions, diapirs would take 10,000 to 100,000 years to rise from the Moho to the upper crust. The trip from the melt zone of a subducting plate to the upper crust would take 100,000 to 1 million years under Weinberg and Podladchikov's conditions. As an alternative to both dikes and diapirs, Weinberg and Searle (1998) proposed that sheets of granitic magma slowly coalesced to form the Pangong Injection Complex in India. Although the emplacement of granites by dikes is currently popular among both scientists and YECs (Clemens, 1998; Snelling and Woodmorappe, 1998), it is doubtful that dikes will explain the emplacement of every granitic rock (for example, Weinberg and Searle, 1998). However, YECs will never accept the current alternatives to dike emplacement (as examples, Weinberg and Searle, 1998 and Weinberg and Podladchikov, 1994) because they are not fast enough for their YEC time frames.

Although Snelling and Woodmorappe (1998) have shown that the ascent of magma could occur in less than 10,000 years, magma emplacement only represents part of the formation of a granitic pluton. Magmas must also form from the melting of parent rocks and finally they must cool. For example, Clemens (1998, p. 848) notes that a 1 km long dike that is 3 meters wide could supply a growing pluton with 1000 km3 of magma in about 1200 years. However, solidification of the pluton would take at least 25 times longer (30,000 years). Pitcher (1997, p. 222) and others still maintain that the entire process of pluton development would typically take 5-10 million years. These values are not only supported by various melting, conductivity/convection, and cooling models, but also by radiometric dating (Pitcher, 1997, chapter 12).

Snelling and Woodmorappe (1998) cite many references that indicate that small plutons can cool within the time demands of YEC, but they often ignore or cover up other information in these references that they don't like. For example, Strahler (1987, p. 213), Pitcher (1993, p. 182; 1997, p. 215-216), and Snelling and Woodmorappe (1998, p. 531) all cite Spera's magma cooling model (Spera, 1980). (It should be stated that both Pitcher (1993, 1997) and Snelling and Woodmorappe (1998) erroneously refer to Spera's paper as having been written in 1982). Spera (1980, p. 301) indicates that a pluton with a radius of 5 km and a water content of 0.5 wt% would cool in 330,000 years, while 4 wt% water would reduce the cooling time to only about 50,000 years. Strahler (1987, p. 213) refers to the 50,000 years, but not surprisingly, Snelling and Woodmorappe (1998) never mention the dates associated with the cooling time calculations in Spera (1980), since even the reduced ages still exceed the allotted YEC age for the Earth. Snelling and Woodmorappe (1998) even perform calculations to avoid mentioning the long cooling times in Spera (1980). Specifically, Snelling and Woodmorappe (1998, p. 531) mention an example from Spera (1980, p. 300), which involves a 10 km wide pluton at 7 km depth and with 2 wt% water. Spera (1980, p. 300) states that the cooling time for the pluton would decrease from 3,600,000 years to 200,000 years if a contact temperature of 500C was used instead of 700C. (The contact temperature refers to the temperature at the contact between the pluton and the rocks surrounding the pluton.) To avoid mentioning the long ages, Snelling and Woodmorappe (1998, p. 531) do some math and simply indicate that there is an 18 fold decrease in the cooling time in this example.

Snelling and Woodmorappe (1998) also cite modeling data out of Hayba and Ingebritsen (1997) to indicate that a hypothetical 2 x 1 km pluton at 2 km depth and with a permeability of 33 millidarcies (md) would cool in only about 3,500 years. However, Snelling and Woodmorappe (1998) largely ignore the numerous examples in Hayba and Ingebritsen (1997) of larger and/or less permeable plutons that would take 10,000 to 25,000 years or even longer to cool below 150C. For example, surrounding rocks with a permeability of 10 to -15 m² that are located 25 meters above a 2 x 1 kilometer pluton which is at a depth of 2 km would take more than 20,000 years to cool to below 150C. Hayba and Ingebritsen (1997, p. 12,238) also conclude that, depending upon permeability, a hydrothermal system around a single 2 x 1 km cooling pluton could remain active over approximately 30,000 to less than 10,000 years. Because even larger plutons in the Canadian Precambrian shield and northern Appalachians, as examples, are geologically dead, it's not surprising that Snelling and Woodmorappe (1998) ignore comments in Hayba and Ingebritsen (1997) about cooling plutons and hydrothermal systems that would easily exceed YEC time limits. While small plutons may form, emplace and cool within Snelling and Woodmorappe's YEC time demands, the geologic record, especially the Precambrian, is full of large and cold plutons that obviously could not have formed and cooled in only a few thousand years. Snelling and Woodmorappe (1998) conveniently ignore the long ages associated with these huge plutons. As further examples, Paterson and Tobisch (1992, p. 293) list the cooling times of a number of large plutons, including the Quottoon Batholith of British Columbia (700 to 450C) (2 million years), the Separation Point Batholith of New Zealand (700 to 450C) (2 million years), and the Sierra Nevada Batholith of California (more than 10 million years).

Snelling and Woodmorappe (1998, p. 538-539) cite a number of references (as examples: Brandeis and Jaupart, 1987; Dunbar et a1., 1995; Swanson, 1977; Swanson and Fenn, 1986; London, 1992; Chakoumakos and Lumpkin, 1990) and conclude that crystals in either gabbroic or granitic plutons could easily grow to their observed sizes within a few thousand years. The typical cooling rates in Snelling and Woodmorappe (1998, p. 539) and their references are between 10 exp -6 to 10 exp -10 cm/sec. However, Snelling and Woodmorappe (1998) may be overly optimistic about fast crystallization rates. Other references do not support their claims. As examples, Paterson and Tobisch (1992) and Cashman (1990) reviewed the literature for field and experimental data on crystal growth rates in some detail. After reviewing all of the data, including some of the same references used by Snelling and Woodmorappe (1998), Cashman (1990, p. 302) concluded that the growth rates for most plagioclase and olivine crystals are only 10 exp-10 to 10 exp-11 cm/sec. Paterson and Tobisch (1992, p. 294) admit that by using typical values in Cashman (1990), a large 10 cm crystal could grow in about 33,000 years. However, Paterson and Tobisch (1992, p. 294) state that 33,000 years may be too fast, since parts of the growing crystals could resorb into the magma or the growth rates may vary over time. Paterson and Tobisch (1992, p. 294) conclude that all pluton crystals could grow to their observed sizes within a few 100,000 years. Of course, this time span is too long for YEC.

In yet another example of selective quoting, Snelling and Woodmorappe (1998, p. 531) cite Marsh (1989, p. 523-524) and note that an hypothetical magma ocean about 10 kilometers thick could solidify in only 10,000 years. However, Snelling and Woodmorappe (1998) don't mention that Marsh (1989, p. 523-524) also states that if the crust forming on top of the magma ocean is fairly stable, the cooling time would be about 500,000 years rather than only 10,000 years.

In summary, the data indicate that at least some granitic plutons may be emplaced in only a few thousand years by dikes. Geologists should accept the possibility of fast emplacement by dikes because it's based on good data. Modern uniformitarianism (actualism) must accept any scientifically valid evidence, whether it supports rapid events and natural catastrophes or slow processes and old events. That is, it's very possible that many plutons have moved through the crust in only a few thousand years or even much faster. However, this does not mean that the Earth is only a few thousand years old.

While geologists can accept rapid natural events, the religious dogma of YECs prevent them from accepting any scientific data that support slower events on an ancient Earth. The problem becomes even worse for YECs, when they consider the origin of Precambrian granites. YECs, like Gentry (1988, p. 133, 184-185), have traditionally viewed Precambrian granites as forming during the six days of the "Creation Week" and in particular on the first and third days. Instead of worrying about how plutons could form in only a few hours to days during the "Creation Week," YECs simply rely on the countless miracles that supposedly occurred during this week. Snelling and Woodmorappe (1998, p. 530) also join with other YECs and claim that some igneous lithologies had supernatural origins during the "Creation Week." Not only is this miracle-filled "Creation Week" unnecessary, dogmatic and anti-scientific, it's utterly hypocritical. Precambrian granites have much the same mineralogies, textures and structures as Cretaceous and other Phanerozoic granites, yet YEC dogma arbitrarily insists that Precambrian granites had a miraculous origin within a few days or less while Phanerozoic granites supposedly formed naturally over a maximum of a few thousand years.

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References

Brandeis, G. and C. Jaupart, 1987.

"The Kinetics of Nucleation and Crystal Growth and Scaling Laws for Magmatic Crystallization," Contributions to Mineralogy and Petrology, v. 96, p. 24-34.

Cashman, K. V., 1990.

"Textural Constraints of the Kinetics of Crystallization of Igneous Rocks," chapter 10, Reviews in Mineralogy, v. 24, p. 259-314.

Chakowmaks, B. C. and G.R. Lumpkin, 1990.

"Pressure-Temperature Constraints on the Crystallization of the Harding Pegmatite, Taos County, New Mexico," Canadian Mineralogist, v. 28, p. 287-298.

Clemens, J. D. and C.K. Mawer, 1992.

"Granitic Magma Transport by Fracture Propagation," Tectonophysics, v. 204, p. 339-360.

Clemens, J. D., 1998.

"Observations on the Origins and Ascent Mechanisms of Granitic Magmas," Journal of the Geological Society, London, v. 155, p. 843-851.

Dunbar, N. W.; G. K. Jacobs and M. T. Naney, 1995.

"Crystallization Processes in an Artificial Magma: Variations in Crystal Shape, Growth Rate and Composition with Melt Cooling History," Contributions to Mineralogy and Petrology, v. 120, p. 412-425.

Eaton, J. P., 1962.

"Crustal Structure and Volcanism in Hawaii," in G.A. MacDonald and H. Kuno (eds.), "The Crust of the Pacific Basin," Geophys. Monograph, American Geophys. Union, v. 6, p. 13-29.

Gentry, R. V., 1988.

Creation's Tiny Mystery, Earth Science Associates, Knoxville, TN.

Hayba, D. O. and S. E. Ingebritsen, 1997.

"Multiphase Groundwater Flow near Cooling Plutons," Journal of Geophysical Research, v. 102, p. 12,235-12,252.

Hyndman, D. W., 1985.

Petrology of Igneous and Metamorphic Rocks, 2nd ed., McGraw-Hill Publishing Co., New York.

London, D., 1992.

"The Application of Experimental Petrology to the Genesis and Crystallization of Granitic Pegmatites," Canadian Mineralogist, v. 30, p. 499-540.

Marsh, B. D., 1989.

"Convective Style and Vigour in Magma Chambers," Journal of Petrology, v. 30, n. 3, p. 479-530.

Paterson, S. R. and O. T. Tibisch, 1992.

"Rates of Processes in Magmatic Arcs: Implications for the Timing and Nature of Pluton Emplacement and Wall Rock Deformation," Journal of Structural Geology, v. 14, p. 291-300.

Pitcher, W. S., 1993.

The Nature and Origin of Granite, Blackie Academic & Professional, London.

Pitcher, W. S., 1997.

The Nature and Origin of Granite, 2nd ed., Chapman & Hall, London.

Ramberg, H.,1963.

"Experimental Study of Gravity Tectonics by Means of Centrifugal Models," Bulletin Geological Institute, University of Uppsala, v. 62, p. 1-97.

Snelling, A. A. and J. Woodmorappe, 1998.

"The Cooling of Thick Igneous Bodies on a Young Earth," Proceedings of the Fourth International Conference on Creationism, Aug. 3-8, Pittsburgh, PA, USA, Technical Symposium Sessions, R. E. Walsh (ed.), Creation Science Fellowship, Inc., 705 Washington Dr., Pittsburgh, PA, USA 15229, p. 527-545.

Spera, F., 1980.

"Thermal Evolution of Plutons: A Parameterized Approach," Science, v. 207, p. 299-301.

Strahler, A. N., 1987.

Science and Earth History, Prometheus Books, Buffalo, NY, p. 232-233.

Swanson, S. E., 1977.

"Relation of Nucleation and Crystal-Growth Rate to the Development of Granitic Textures," American Mineralogist, v. 62, p. 966-978.

Swanson, S. E. and P. M. Fenn, 1986.

"Quartz Crystallization in Igneous Rocks," American Mineralogist, v. 71, p. 331-342.

Weinberg, R. F. and Y. Podladchikov, 1994.

"Diapiric Ascent of Magmas through Power Law Crust and Mantle," Journal of Geophysical Research, v. 99, p. 9543-9559.

Weinberg, R. F. and M. P. Searle, 1998.

"The Pangong Injection Complex, Indian Karakoram: A Case of Pervasive Granite Flow through Hot Viscous Crust," Journal of the Geological Society, London, v. 155, p. 883-891.

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