Equal Time For The Origin Of Granite - A Miracle!
Lorence G. Collins
The creationists are asking for equal time in science classrooms to teach that the Genesis stories are valid scientific interpretations of earth history. Equal time for creationists' interpretations are not likely to occur in secular universities and schools, but if the creationist are serious about equal time, then they should be open to granting equal time in their private Christian schools for presentations of both sides of a scientific issue --- a literalist biblical view and the modern science view. The origin, age, and other characteristic features of granite are such issues deserving equal time. The Bible says that the dry land was created on the Third Day of the Genesis Week (Genesis 1:9-10), and presumably, this is the time in which granite in continental masses was formed. If I were given equal time in a science classroom at a private, fundamentalist, Christian college or secondary school, advocating creationists' views, the following would be the kinds of information that I would provide for a modern scientific interpretation of granite to compare with the corresponding creationists' biblical interpretation.
Origin. Geologists recognize that granite has several possible origins, depending upon the processes that operate on the rock systems. Some granites form (1) by magmatic processes, depending upon crystal settling and the order of crystallization of minerals from a magma (melted silicate rock), (2) by melting of sedimentary rocks whose chemical composition is the same as that in granite, (3) by partial melting of rocks in which the first minerals to melt have the composition of granite, and, finally, (4) by chemical replacement processes (Clark, 1992; Collins, 1988; Hunt et al., 1992). Discussion of these different origins is not further expanded here because of space limitations and because it is sufficient to say that modern scientific studies show that granite is formed in many different ways, and these ways contrast with the creationists' model in which granite has a single origin, being created nearly instantly by "fiat" (e.g., Gentry, 1988).
Mineral composition. Granite, a relatively coarse-grained igneous rock, is not a pure substance but is a mixture of several different silicate minerals and oxides (Clarke, 1992). It commonly consists of about one-third quartz, one-third potassium feldspar, one-third plagioclase feldspar, minor amounts of iron- and magnesium-bearing biotite (black mica), and traces of various accessory minerals, including zircon (mentioned later). In addition to biotite, other varieties of granite may contain small amounts of other iron- and magnesium-bearing silicates or muscovite mica, but biotite granite is the most common variety. In all granites, however, quartz and feldspars are the dominant mineral species, making the rock white, light cream, or pink, but speckled with one or more of the dark iron-bearing minerals.
Liquid characteristics. In the field, granite can be seen to intrude other rocks and in some places to exhibit flow banding, both of which are possible characteristics of moving liquids or plastic solids. In many places, however, fragments of older rock along the walls of a granite body are broken off and enclosed in the granite body when it was first formed. Finally, if a granite body has a liquid origin, it should have the capability of mixing with other liquids, such as basalt magma, and this clearly occurs, for example, in Maine (Wiebe, 1996) and in other parts of the world (cited in Wiebe, 1996).
Order of crystallization. Experimental work in which natural granites are melted in the laboratory shows that when a granite is in a liquid state, it would have been a water-bearing silicate melt (magma) at temperatures as high or higher than 900 degrees C (Huang and Wyllie, 1981). When this silicate melt is cooled and crystallized to become granite, not all of its various minerals crystallize at the same time, but each forms in a specific range of temperatures and in a definite order. The iron-, magnesium-, and titanium-bearing silicates and oxides crystallize at relatively high temperatures whereas the feldspars form at lower temperatures, and quartz is the last to crystallize near 550-650 degrees C, depending upon pressure and other components. This order of crystallization is consistent world-wide regardless of whether the granite is Precambrian in age or younger.
Evidence for high temperature of natural granites. Geologists find evidence for the high-temperature crystallization of a granite body by using what are called "geologic thermometers." For example, in experimental work in which biotite mica and garnet are crystallized simultaneously from melts, it is found that iron and magnesium atoms are partitioned from the melt into these two minerals in different ratios and that these ratios are variable and functions of different temperature and pressure conditions (Ferry and Spear, 1978). By measuring these ratios in coexisting biotite and garnet in natural granites and comparing them with ratios obtained at different temperatures and pressures in the experimental work, geologists find that the temperatures for the final crystallization of these two minerals in natural granites are commonly higher than 700 degrees C. Several "geologic thermometers" exist that have experimental support and which can be applied to other coexisting mineral pairs in granites (Bohlen and Lindsley, 1987). All indicate that the granites crystallize at high temperatures.
As further evidence of the high temperature origin of granite is the contact metamorphic aureole that occurs in sedimentary rocks where they are intruded by granite magma. The minerals found in sediments are generally stable near 25 degrees C and one atmosphere of pressure and result from weathering processes at the earth's surface. When these minerals are heated to temperatures approaching those of an adjacent hot granite magma, some will remain as the same mineral but will recrystallize and increase in size while others will form new minerals that are stable at high temperatures and pressures. For example, find-grained fossil-bearing limestones that consist of calcite (calcium carbonate), which are intruded by granite magma, commonly recrystallize as coarse-grained calcite marbles; in this process the fossils are destroyed as the tiny calcite crystals in the fossils grow in size. On the other hand, sedimentary shales, consisting mostly of aluminum-rich clay, are recrystallized to form other aluminum-rich minerals, some of which are stable at the highest temperatures closest to the granite contact; others are stable at intermediate temperatures at greater distances away; and still others are stable at lower temperatures at even farther distances from the contact (e.g., Pitcher and Berger, 1972; Holtta, 1995). Such aureoles (a few meters to a 1,000 meters or more) of high-temperature contact-metamorphism of sedimentary wall rocks are found world-wide around most granite bodies of large size and support the concept that these granite bodies were intruded as a very hot magma.
Age of granites. The field evidence supports the concept that all granites are not formed at the same time as other rocks with which they may be adjacent and that some granite bodies are younger in age than other granites. The fact that granite bodies intrude other rocks (by filling in cracks, for example, to form dikes) indicates that the other rocks are older in age than the granite. The intruded rocks have to be there first before the granite can cut through them. In some places granite masses of one type cut across other granite bodies, which also shows that some granites are younger than others. The fact that granites also have several possible different origins, as described earlier, also implies different ages of granite. For example, if some granites are derived by melting of sediments, erosion of a continental land mass must occur first to produce the sediments. Then, the sediments must be deeply buried, and a strong heat source must be found before the granite can be formed from them. At any rate, it is clear that all granites are not formed necessarily at the same time as in Day Three of the Genesis Week.
Precambrian granite bodies in the bottom of the Grand Canyon in Colorado have an erosion surface on which the horizontal, Paleozoic, fossil-bearing sediments are deposited, with the Cambrian Tapeats sandstone at the bottom and the Permian Kaibab limestone at the top. The eroded surface indicates that these granites are older than these sediments, the so-called "Noachian Flood deposits." On the other hand, the Donegal granites in northwest Ireland intrude and enclose inclusions of sedimentary rocks of Cambrian age, illustrating that the granites are younger than the Cambrian deposits, whose contacts with the granites have a high-temperature metamorphic aureole (Pitcher and Berger, 1972). The same kinds of metamorphic contact-relationships are found in the granites that intrude fossil-bearing sediments in Maine, Connecticut, and Rhode Island (Harrison et al., 1983). The Narragansett Pier granite in Rhode Island surrounds inclusions of Pennsylvanian metamorphosed sediments containing flora fossils, Annularia stellata (Brown et al., 1978). The flora fossils are now totally carbonized as graphite, indicating the high temperature of the granite body that metamorphosed the sedimentary inclusions. The fact that the granite contains inclusions of these fossil-bearing sediments makes the granite younger than these supposed "Flood" sediments. The Sierra Nevada granite intrusions in California also have intruded and metamorphosed supposed "Flood sediments" in roof pendants containing Ordovician graptolite fossils (Frazier et al., 1986) and Pennsylvanian brachiopod fossils (Rinehart and Ross, 1964; Rinehart et al., 1959). In other places, the Sierran granites have intruded and metamorphosed "Flood sediments" containing Triassic ammonites (coiled cephalopods) (Smith, 1927). A granite in the Mojave desert in California near Cadiz intrudes Cambrian limestone containing stromatolite fossils. At the contact, this limestone is converted to marble with high-temperature metamorphic minerals, but remnants of the stromatolites can still be found (Richard Squires, oral communication, 1998). Thus, it is very clear from the above examples that some granite masses are the same age as or even younger than the "Noachian Flood deposits."
Absolute ages of granite bodies, rather than relative ages, can be obtained by using various radioactive isotopes; i.e., uranium-lead (U-Pb), potassium-argon (K-Ar), and rubidium-strontium (Rb-Sr) age-dating techniques. For example, trace amounts of uranium and lead are dissolved in the granite melts. Uranium and lead ions have entirely different chemical characteristics, and they normally crystallize in entirely different minerals. Because the uranium ion is about the same size as the zirconium ion, uranium will substitute for zirconium and crystallize in zircon, but the lead ion goes elsewhere, commonly in potassium feldspar, as the granite magma crystallizes. But the isotope of uranium (238U) is radioactive and eventually decays to form lead (206Pb). When the granite first crystallizes and the radioactive uranium enters the zircon crystal (devoid of 206Pb), the clock is set and "ticking," and the uranium is constantly breaking down, eventually to produce new lead (206Pb) atoms trapped in the zircon crystals. Because this U-Pb decay-scheme is a constant, the ratio of uranium to lead in zircon populations in granite can be used to determine the age of a granite. World-wide the absolute ages of various granite bodies are consistent with the relative ages described above. Granites in the bottom of the Grand Canyon give Precambrian ages of 1.58 and 1.65 billion years, younger than the 1.7-1.85 billion-year-old Vishnu schist (Livingston et al., 1974), which the granites intrude, (and older than the overlying "Noachian Flood deposits" of about 540 million years for the Cambrian Tapeats sandstone at the bottom to the 225 million-year-old Permian Kaibab limestone at the top. The Narragansett Pier granite that contains 300 million-year-old Pennsylvanian flora fossils (Brown et al., 1978) indicates that this granite is younger than the sediments, and this is confirmed by the U-Pb age-date from zircon populations of 273 million years (Zartman and Hermes, 1987). And granites in the Sierra Nevada give Jurassic and Cretaceous ages of 66 to 208 million-years-old that are younger than the rocks (about 230 million years-old) containing upper Triassic ammonites, which these granites intrude.
Occasionally, some granites give apparently anomalous isotopic "ages," including even some of which indicate an age greater than the 4.5 billion-year-age of the earth. This fact is commonly harped on by creationists who are critical of isotopic age-dating methods. But in these places logical explanations suggest reasons why the dates are unusual. Close examination generally shows that, where unusual age "dates" are obtained from granite samples, other processes have affected the granite to cause the anomalous dates. For example, the granite may have been deformed and fractured so that fluids have entered and altered the isotopic ratios. Where granites have been dated by the Rb-Sr age-dating method, anomalous measurements are not unusual because of the susceptibility of rubidium and strontium to be added or subtracted by introduced fluids moving through fractures and deformed crystals in the granite (Collins, 1988; Hunt et al., 1992). The K-Ar age-dating method can also give values that differ from U-Pb age measurements because heat generated from the intrusion of another nearby igneous mass has allowed some of the argon gas to leak. In each of these places, the unusual or unexpected age dates is not the failure of the dating method, but an indication that other events have occurred in the geologic history of these rocks.
Geologists realize that apparently inconsistent "dates" can occur and seek to find out why they occur, knowing that the isotopic age-dating technique, itself, is not at fault. For example, the following analogy can be used. Water-proof wrist watches that can be worn by scuba divers generally keep good time, but occasionally these watches fail and give faulty time. When that happens, an examination of the watch shows that it has been damaged so that a crack in the holding case has occurred, and water has leaked into the clock mechanism. The faulty time is not because the watch is improperly designed but because water has corroded the gears in the clock. On that basis, a person does not throw out all clocks or watches or cease to buy them. Likewise, when isotopic age-dating of granites or other igneous rocks produces unexpected or illogical age dates, one does not throw out the whole system of isotopic age-dating. In some disturbed and deformed rocks, the "clock timing mechanism" has been "upset" by "corrosion" or some other factor, and the faulty date is a clue to the geologist to look for the cause. The primary reason for accepting the isotopic age-dating methods is because, in many places, world-wide, where several different kinds of isotopic age-dating methods have been applied to the same rock, all age determinations were found to be the same. This equality of measured dates gives confidence that the isotopic age-dating methods are valid scientific procedures. The vastly different half-lives of the radioactive isostopes in each age-dating method and the completely different chemical characteristics of the isotopes make the coincidence of producing the same age dates not a pure-chance situation. The age dates must be controlled by physical laws that are very dependable.
Heat capacity of granite. Measurements can be made to determine the heat capacity of a block of granite at a given temperature and also to determine the rate of heat conduction as such a block cools from a higher to a lower temperature. Such laboratory measurements are commonly done by using a calorimeter, and they show that blocks of granite are very poor conductors of heat. If a body of granite magma had a surface area of 30 to 50 square kilometers and a depth of 20 to 35 kilometers (a typical size of a small granite body), the total amount of heat (calories) stored in such a granite mass at a temperature of 900 degrees C is enormous. But, significantly, the heat conduction experiments show that the rate at which the heat is lost by conduction must be very slow. Calculations show that such a volume of granite magma would take several millions of years to cool down from 900 degrees C to near 550-650 degrees C, where it would totally crystallize, and then finally to cool to the 25 degrees C temperature found at the earth's surface. Pitcher (1993) estimates that a granite body, depending upon its size and depth of burial, cools no faster than 25 to 250 degrees Centigrade per million years. This slow cooling is indicated by deeply buried granite magma still giving off heat in the Coso Range of east-central California, containing rhyolite flows (volcanic equivalent of granite); the residual heat is being utilized for steam generation and electrical energy.
When creationists make a literal interpretation of the Genesis accounts for the origin of granite (e.g., Gentry, 1988), they are not seeking to collect new data. The literalists accept the Genesis accounts as being accurate, requiring no questions or further research. Therefore, creationists are selective in choosing only the scientific data that fit their model of creation and discard everything else. This procedure is not characteristic of the scientific method.
The creationists' interpretation of granite, when applied to Genesis 1:9-10, is that all granite masses are formed on Day Three of the Genesis Week and emplaced at relatively cold temperatures. This interpretation is not supported by field evidence, microscopic studies, and experimental work and is clearly not accurate because some granite must have been produced at different times later than Day Three, either during or after the supposed Noachian Flood. Moreover, if Precambrian granite were produced nearly instantaneously during Day Three, all physical laws would have to be abandoned, and this granite must have been created by a miracle. Even if creationists acknowledge that some granite was produced during and after the Noachian Flood, and they cannot deny the evidence, then all physical laws for cooling rates and crystallization would also have to be ignored, because such granites could not be emplaced and solidified in less than one year and not even 6,000 to 10,000 years, if the physical laws governing crystallization and cooling rates are obeyed. Furthermore, if all the heat from the world-wide granite masses that penetrated the supposed Flood sediments were released suddenly in one year's time to the Noachian Flood waters in order to crystallize the granite masses abruptly, the waters would be heated so hot that the oceans would be boiling and no marine life would survive. Funny that Noah never commented on this phenomenon! One can teach a rapid formation of granite, but it is not teaching science. The literalist interpretation has to be saying that all granite bodies are formed by miracles.
Equal time, when used to discuss the origin of granite, clearly shows that the creationists' literal interpretation of the Genesis stories in the Bible has no validity for presentation in the science classrooms at secular schools because it is not science. It may have a place in some Christian schools where science is taught as miracles.
I wish to thank Calvin Stevens, Stanley Finney, Kurt Hollocher, and Richard Squires for help in locating references indicating presence of fossils in wall rocks penetrated by granite, Peter Weigand for assistance in locating references containing isotopic age dates, and Barbara Collins and J. F. Kenney for editorial suggestions.
Dr. Lorence G. Collins Department of Geological Sciences California State University Northridge 18111 Nordhoff Street Northridge, CA 91330-8266 FAX 818-677-2820