Core-Mantle Boundary and Creationism

Core-Mantle Boundary (CBM)                Irregular interface about 1,800 miles (around 2,890 kilometers) below the Earth’s surface marked by seismic discontinuities that was long believed to be a simple, homogeneous division between solid silicate rock of the mantle and liquid iron alloy of the outer core. Within the past several decades, intensive geophysical and geochemical research has shown the CMB to be considerably more active, complex, and heterogeneous and that it may hold the key to understanding numerous geophysical phenomena, including the formation of mantle plumes, various core-mantle interactions, the behavior of the Earth’s electro-magnetic field, and the ultimate fate of subducting crustal slabs driven into the Earth’s mantle by tectonic forces. Having stated that, it is critical for Readers to realize that the distance from the surface and resulting extreme temperature and pressure conditions in the CMB make data collection and interpretation particularly challenging. The pressures are up to 135 gigapascals and temperatures probably range between 2000° K and 4000° K, conditions that are extraordinarily difficult to reproduce in the laboratory. Despite those enormous challenges, laboratory experiments, seismic wave analysis, computer simulations, and geophysical-geochemical theory are finally working together to bring the CMB into sharper focus.

Several teams of research scientists (Iitaka et al, Oganov and Ono, Murakami et al, Hirose et al, Shieh et al, and Tsuchiya et al)  have recently linked the calculated physical properties of a newly discovered high-pressure crystal structure, called a post-perovskite phase, with seismic observations of the deep lower mantle. Other scientists from the United States and Canada have recently proposed a new layer in the model of Earth’s interior, essentially a sort of fuzzy zone with properties of both the outer core and lower mantle that at least in certain areas may neither be sharp nor homogeneous. That new theory involves a conducting layer at the CMB that could explain both the Earth’s wobble and the newly discovered zones of low seismic velocity in the lower mantle. However, the process of relating seismological observations to the dynamics, chemistry, and evolution of the CMB is just beginning. Therefore, none of the information cited in this blog should be taken as firmly established or universally accepted. That area of research is truly cutting-edge and should be followed carefully in the professional literature to see what shakes out. Author’s Note: The CMB is also widely known as the D’’ (or D prime-prime) layer, which was the name applied in 1949 to the 200-kilometer thick area by the New Zealand geophysicist Keith Bullen, who geoscientists may recognize as co-author of the Jeffreys-Bullen Travel Time Tables.

Additional Background: In 2001, researchers Sebastian Rost and Justin Revenaugh of the University of California — Santa Cruz studied seismic shear waves that had been generated by earthquakes near the islands of Tonga and Fiji in the South Pacific and were recorded by an array of instruments in Australia. They found evidence of a thin core-rigidity zone and small patches of rigid material at the edge of the fluid outer core where the outermost core was more solid than fluid. Their findings indicated that the boundary between the core and the mantle may not be as sharply defined as was once thought. In October 2002, Richard A. Muller, a professor of physics at University of California — Berkeley, published “Avalanches at the Core-Mantle Boundary” in Geophysical Research Letters. In that research he identified what he considered to be the most plausible hypothesis yet of what was behind geomagnetic field reversals and possibly how bolide (asteroid or comet) impacts and disrupted convection currents at the CMB may be responsible for flood basalts and large igneous provinces. Without going into all the details, Muller’s basic argument is as follows.

• The Earth’s magnetic field is caused by convection currents in the liquid outer core.
• Those currents constitute an amplifying, self-sustaining geodynamo.
• Convection probably starts as iron crystallizes on the surface of the solid inner core and lighter components like oxygen, silicon, and sulfur separate and rise through the liquid outer core toward the CMB, where temperatures are about a thousand degrees cooler.
• The lighter components cool and condense as slushy “sediments” at the CMB.
• Perhaps tens of meters of those buoyant sediments accumulate each million years, at the mantle’s uneven bottom layer.
• Even if the irregular slopes of the CMB “topography” are shallow, eventually the materials will slip and slide as the mixture of cooler sediments and hot liquid iron causes cooled-off, denser iron to sink back toward the inner core.
• The sinking iron would disturb the geodynamo’s convection cells, causing frequent “excursions” or reversals of the dipolar magnetic field as measured at the surface.

However, a truly massive CMB “avalanche” and the resulting convection cells could disrupt the geodynamo and cause Earth’s dipole field to collapse. And, if the mantle became hot enough, a magma plume might be sufficiently powerful to extend all the way to Earth’s surface.

Rare events, such as when a massive asteroid or comet crashed into the Earth at a sufficiently oblique angle, could trigger enormous avalanches at the CMB. When that happened, the lower mantle would jerk sideways from the force of the transferred momentum, shearing off whole mountains of accumulated sediment and releasing a downward-sinking mass of cool iron that could completely destabilize the large convection cells. Hot iron would heat the exposed mantle rapidly; within a few million years or less a plume of magma could rise through the mantle to the crust in the enormous eruptions known as fissure flows or large igneous provinces.

According to Muller, if a powerful oblique bolide impact would strip most of the CMB of its insulating sediments, that event would be followed not only by enormous flood basalts and by a very long period without any magnetic field reversals because of the time needed to collect sufficient sediment for new CMB avalanches to occur.

Muller’s theory therefore predicted that a long normal period in Earth history without magnetic field reversals would be preceded by a huge basalt flow coincident with the beginning of the long normal period. A colleague of his at UC — Berkeley, the geologist Walter Alvarez, one of the scientists who proposed the impact theory of the Cretaceous-Tertiary extinctions, pointed out that the formation 120 mya of one of the largest flood basalt districts in the world, the Ontong-Java Plateau, precisely coincided with the onset of the long normal period. It was not proof by any means but certainly was encouraging information.

Additional Author’s Note: Remember, at this point Muller’s work remains a fascinating theory. But it’s one interested readers should follow carefully. Under the very same topic, geoscience students should also keep their eyes on the diamond-anvil-cell experiments of Raymond Jeanloz at the University of California — Berkeley, the computer simulations by Gary Glatzmaier of University of California — Santa Cruz and Los Alamos Lab, and the Ultra Low-Velocity Zone research by Ed Garnero (Arizona State) and Quentin Williams (University of California — Santa Cruz) and others. They may or may not support Muller’s conclusions but they deal with very closely related geophysical ideas and issues.

Creationism (Creation Science)             Two (often overlapping) types of ideas are loosely called creationism: Biblical Creation and Scientific Creation. Author’s Note: The materials immediately below have been taken verbatim from web sites, especially www.creationism.org, that express those opinions and are NOT to be mistaken for beliefs I hold dear.

Biblical Creation: Using Bible texts to defend creation theory. A few primary texts include: Genesis, chapters 1 to 12 - from the 6 days of Creation till the Great Flood (1700 years later), then until just after the Tower of Babel and the dispersion of the nations. Exodus 20:11 (in the middle of the Ten Commandments, this verse states in part: “For in six days the Lord made heaven and earth, the sea, and all that in them is, and rested the seventh day....” Also, Luke 17:26-27 (or Matt. 24:37-39) “And as it was in the days of Noah, so shall it be also in the days of the Son of man. They did eat, they drank, they married wives, they were given in marriage, until the day that Noah entered into the ark, and the flood came, and destroyed them all.” (This statement by Christ shows that He considered the Great Flood to be a real historical event, one of Divine judgment of humankind.) And I Corinthians 15:45, which compares Adam (as a literal person) to Christ as the ‘last Adam.’

There are also many Psalms and other texts referring back to the creation. It should be noted that the book of the Bible that is most quoted in all the rest of the Bible is: Genesis. Thus the Book of Genesis is seen as not only integral to the whole, but foundationally essential for Jews, Christians, and others of faith. Now then, interpretations of Genesis may vary widely (particularly for its first three chapters, Gen. 1-3) but the original text has been codified for thousands of years.

Scientific Creation: Yes, we often use science – completely independent of any Bible references – to contend that ‘creation science’ is a plausible scientific theory. Many persons laugh at this notion at the outset but please be advised that informed creationists usually beat evolutionists in debates. We are the ones who have science on our side.

The majority of modern scientists, just like the rest of the human race, are unrepentant sinners. As such they do not want to face God. Humans often hide rather than face judgment. (Evolution provides a great hiding place.) Creationists can show evolution’s frauds and deceptions time after time, after time but it will remain an uphill battle to get the truth out regarding our origins as made (unique from the animals and) ‘in the image of God’ and human responsibility for our sins.

Author’s Rant: Whew! It’s hard for me to read crap like that and not become irritated. Just remember, uninformed opinions are like assholes; we all have them. For a lighthearted but spirited refutation of creationist misconceptions of Earth history, call your local library (or check out their catalogue on the internet) and see if they have Creation/Evolution Satiricon: Creationism Bashed. It’s written by the well-known marine geologist and geomorphologist Robert S. Dietz and illustrated by John C. Holden. Stephen G. Brush, a historian of science, examines scientific theories for dating the age of the Earth, particularly radiometric dating, in Transmuted Past: The Age of the Earth and the Evolutions of the Elements from Lyell to Patterson; Volume 2 in the series, A History of Modern Planetary Physics. Cambridge University Press, 1996. For a shorter but hardly less lucid critique of irrational claims by creationists that the Earth is only a few thousand years old, coupled with an exposition of radiometric dating methods, see Stephen G. Brush, “Finding the Age of the Earth by Physics or by Faith,” Journal of Geological Education, vol. 30, pp. 34-58, 1982.

In a challenging book intended for the lay audience, G. Brent Dalrymple reviews scientific evidence for the age of the Earth, Moon, and Solar system in such well documented and critical manner that it leaves no room for uncertainty or doubt: The Age of the Earth, Stanford, California: Stanford University Press, 1991. The book’s greatest virtue is its detailed analysis of radiometric dating methods. The many, many examples and the exhaustive chronology that are presented reveal how imaginative but sometimes wrong researchers have been in the past. But then he shows how tirelessly other researchers have checked their work, finding errors, and developing more reliable methods. It is also clear that the results of proven techniques have been checked rigorously against the results of other methods, until there can be little scientific doubt about the final conclusions. One cannot read that book with an open mind and continue believing a few warped scientists conspired to conjure up a patently false system and that hundreds and even thousands of later scientists simply fell into line with and confirmed their bizarre fantasies. Scientists are not easily duped.

Philip Kitcher, a philosopher of science at the University of Vermont, has written a marvelously lucid summary of the evidence for evolution and the overwhelming case against its opponents in a thoughtful and witty attack on ‘scientific creationism, Abusing Science: The Case Against Creationism, Cambridge, MA: MIT Press, Updated March 2001; go online and read the excerpt, “Creationist’s Blind Dates” at: http://chem.tufts.edu/science/Geology/KitcherBlindDates.htm. Kitcher, who as a philosopher is concerned with the way science operates, is particularly adept at showing how creationists distort Karl Popper’s views on scientific method and how they misuse such books as Thomas Kuhn’s Structure of Scientific Revolutions.

Of course, readers interested in the geoscience side of the argument over creationism should read Arthur N. Strahler’s marvelously written and well-reasoned, Science and Earth History: The Evolution/Creation Controversy, 2^nd ed., Amherst, New York: Prometheus Books, 1999. Strahler was professor of geomorphology in the Department of Geology at Columbia University and author of numerous textbooks in geoscience. His book is a comprehensive treatment of the ongoing conflict between scientists who accept the theory of evolution and creationists. He reviews the philosophy, methods, and sociology of empirical science from astronomy to zoology, contrasting those with the belief systems of religion and pseudoscience. In one very interesting section he establishes sound criteria for distinguishing science from pseudoscience and demonstrates with devastating logic that creation science fails to meet the criteria of scientific enterprise.

A more recent and delightful work based on sound science and leavened with literary grace and elegance is also well worth reading, no matter what your evolutionary point of view, but only if you have an open mind, which from my personal experience is something almost entirely lacking in creationists: Richard Dawkins, The Ancestor’s Tale: A Pilgrimage to the Dawn of Evolution. New York: Houghton Mifflin, 2004. For a very well written and tightly reasoned point of view of a Christian geophysicist, see: Roger C. Wiens, PhD, Radiometric Dating: A Christian Perspective, material originally written in 1994 and revised in 2002: http://www.asa3.org/ASA/resources/Wiens.html. And don’t forget the early and remarkable essay by the evolutionary biologist and devout Russian Orthodox Christian Theodosius Dobzhansky that criticized Young Earth creationism and espoused what he called evolutionary creationism: “Nothing in Biology Makes Sense Except in the Light of Evolution,” American Biology Teacher, vol. 35 125-129, 1973. Note that that article may have been inspired by the work of Jesuit physical anthropologist and philosopher, Pierre Teilhard de Chardin, whom Dobzhansky much admired.

Everyone interested in the cultural war between the adherents of evolution and creationists (in this camp I squarely place those who believe in intelligent design) should read two fairly recent books. The first, by the physical anthropologist Eugenie C. Scott, is Evolution vs. Creationism, Berkeley, California: University of California Press, 2005. It is both a history of the debate and a collection of essays written by partisans from both sides. Its main attribute is its clear explanation of the scientific method and the astronomical, biological, chemical, and geological bases of evolutionary theory. As good as that book is, even better is Michael Ruse’s The Evolution-Creation Struggle, Cambridge, Massachusetts: Harvard University, 2005. As a philosopher of science, Ruse (self-described as an ardent Darwinian) has testified against the inclusion of creationism in public school science curriculums. He cautions all of us on the use of the word “evolution,” especially since it has two meanings: the science of evolution and something he terms evolutionism, which is the part of evolutionary ideas that reaches beyond testable science. In other words, Ruse lays out what is actually a struggle between science and theology that really constitutes a war between two rival metaphysical worlds.

One positive indication, though no one should put much “faith” in it, is that courts at various levels repeatedly have held that public schools must be religiously neutral and must not advocate religious views. In 1987, in Edwards v. Aguillard, the Supreme Court ruled that teaching creationism in the public schools was unconstitutional. And finally, I really wonder if it ever occurred to our creation science and Young Earth friends to explain with scientific rigor how the fossilized marine sedimentary rocks (from the Ordovician) forming the summit of Mount Everest, known locally as Chomolungma, Goddess Mother of the World, got to be nearly 30,000 feet above sea level in less than seven thousand years.

Interested bloggers should consult published articles that discuss the implications of the late-2005 decision of U.S. District Judge John E. Jones III against the Dover Area (Pennsylvania) School District in what may have been a critical test case that ruled intelligent design and creationism are one and the same and have no place in a biological science curriculum and that intelligent design "cannot uncouple itself from its creationist, and thus religious, antecedents", and that the school district's promotion of it violated the Establishment Clause of the First Amendment to the U.S. Constitution.