When the Earth’s crust explodes
By M. Elaine Kennedy
You live in California and you are proud of your beautiful home. It overlooks the blue waters of the Pacific Ocean. One sunny afternoon, you are sitting on your favorite chair on the deck, watching the white waves tirelessly, but rhythmically, beating away now with gentleness, now with thunder. The radio is playing your favorite music, and life seems so quiet, sweet, and enjoyable. Suddenly the music is interrupted. An early warning emergency system goes into operation. A possible volcanic eruption accompanied by earthquake on the rim of the ocean seems imminent, and you along with your neighbors are asked to evacuate to a safer location.
Fiction? Not any more. A ring of volcanic and earthquake activity is being felt around the rim of the Pacific Ocean. Volcanologists, with the help of modern technology, are able to monitor dormant and active volcanos in the Pacific Rim, identify indicators of increased activity that may lead to eruptions, and issue early warning to communities living along the Pacific Coast.
Such an increased understanding of the subsurface processes may also increase the predictive power of the volcanologists. But understanding these processes does not answer the crucial human question, Why does this happen? Other information sources are needed to help us grapple with that issue. The answer remains speculative, but some basic information about the processes that produce some of the molten rock within the earth may be helpful. Since there is a volcanic rim around the Pacific Ocean, this essay will begin by looking at that region.
The ring of fire
Along the margins of the Pacific Ocean there are deep trenches. The Pacific Ocean floor sinks into these trenches and slides below the rocks that form the continental crust. This process is referred to as subduction,1 and volcanologists suggest that this subduction process produces the source material for most of the volcanism surrounding the Pacific Ocean, hence the phrase Ring of Fire. The subducting oceanic slab carries seawater and some crustal material with it. The more deeply these materials are subducted, the higher the temperatures and pressures around the rocks. Eventually the combination of volatiles or gases produced from the seawater and crustal material combined with increasing pressures and temperatures cause melting of the subducted slab and upper mantle.2 The melted rock or magma then begins to rise through the continental crust, generating new, and utilizing old, fractures and faults and incorporating additional crustal material as it moves.3
When the crustal rocks melt, some rock types chemically decompose and release gases such as carbon dioxide and sulfur dioxide. The rising magma may mix with magmas from other sources, which also contribute volatiles. Gases increase the pressure within the magma and decrease its density, which aids in the upward movement of the molten rocks along faults.4 However, molten rock moving along fractures does not mean that a volcano is about to erupt. Vulcanologists look for specific indicators of imminent volcanic activity.
Data on volcanos is collected worldwide because scientists want to know when the next eruption will occur. Information that seems most useful includes seismic (earthquake) activity and types of gases that are emitted. Common gases released from volcanic fissures and craters include sulfur dioxide, carbon monoxide, carbon dioxide, hydrogen sulfide, and water vapor.5 Earthquake activity increases dramatically just prior to an eruption. Most of the activity is about 4 or less on the Richter Scale; however, larger-scale earthquakes can occur with loud noises, liquefaction, and other earthquake-related activity.6 As pressures build within the magma chamber due to the incorporation of volatiles from the surrounding crustal rocks, the potential for eruption increases.7
Eruption occurs when the pressure in the magma chamber exceeds the pressure exerted by the weight of the overlying rocks. Loud explosions and earthquakes often precede and accompany the ejection of lava, incandescent rocks, gases, and ash.8 Once the eruption occurs, many people are interested not only in what happened but also ask, Why did this occur?
Within religious communities, earthquakes and volcanic eruptions have been of interest since they have been commonly referred to as acts of God. Some think that in the past, people attributed volcanoes and earthquakes to God or evil spirits out of ignorance but the Book of Job makes it clear that both God and Satan act in nature (see Job 1:6-12). Now that more is known about the processes involved in the eruptions, people no longer consider such activity as divine or mystical intervention. The Christian community recognizes the difficulty in knowing how or when God might use natural processes to His purpose (see Matthew 21:18-22; Luke 13:4, 5). Thinking that we know how something works does not mean that God is not involved in the timing of the event or the process. The concept is a difficult one since we do not know the mind of God. We do not know if any or all of the events include divine intervention or if most are simply processes that occur randomly in our world. Our lack of knowledge on this topic should lead us to be cautious with our comments about end of the world events and judgments (see Mark 13:8; Luke 21:9-11, 25-28).
Volcanism during the Genesis Flood
There is another aspect of volcanism that should be considered from a biblical-Christian perspective. The continental and oceanic rocks contain an extensive record of volcanism. Seventh-day Adventists believe that most of this record is part of the Genesis flood. The inclusion of volcanism in the Flood account increases the complexity and devastation of that event. (See page 15.) Aerially extensive basalt flows such as the Siberian Traps, Deccan Traps in India, Parana Basalts in Brazil, and the Columbia River Basalts in the northwestern United States, may have begun during or near the end of the Genesis flood. In addition, widespread volcanic ash beds are found interbedded throughout the rock layers of earths crust.
During discussions of the biblical flood, Christians comment on the destructive power of the flood waters but seldom refer to the volcanic and earthquake-related devastation that accompanied that event. As Christian scientists continue to study the geologic record, their awareness of the complexity of the Genesis flood increases.
Very little is really known about the subsurface processes that contribute to volcanism. Most of the theories are developed from surface measurements. As volcanologists attempt to study these processes, they hope to explain why eruptions occur.
Within the Christian community there is an awareness
of a power beyond the physical and chemical processes observed in nature.
The biblical interpretation of volcanos, earthquakes, floods as judgments
causes Christians to question the randomness of events. Many Christians
consider most natural disasters to be random events, part of a sinful
world. The biblical perspective ties these events to the end of the world,
and their occurrence should strengthen our faith in the second coming
of Jesus. A sudden notable increase in the frequency of natural calamities
is predicted just prior to the return of Christ. Although friends and
family may perish during one of these disasters, Christians have faith
in the abiding, undying love of the Father for His children. These processes
remind us of the greatness of Gods power, and His ability to control
the forces of nature.
M. Elaine Kennedy (Ph.D., University of Southern California) is a geologist and an assistant research scientist at the Geoscience Research Institute. Her address: Geoscience Research Institute; Loma Linda, California, 92350; U.S.A. Dialogue has published other articles by Dr. Kennedy: God and Geology in Graduate School (3:3), The Intriguing Dinosaur (5:2), and The Search for Adams Ancestors (8:1).
Articles on related subjects published in this journal: Harold G. Coffin, Coal: How Did It Originate? (6:1); William H. Shea, The Flood: Just a Local Catastrophe? (9:1).
Notes and references
1. See E. J. Tarbuck and F. K. Lutgens, The Earth: An Introduction to Physical Geology (Columbus, Ohio: Merrill Publishing Company, 1987), pp. 481-496. Also, J. Ruiz, C. Freydier, T. McCandless, and R. Bouse, Isotopic Evidence of Evolving Crust and Mantle Contributions for Base Metal Metallogenesis in Convergent Margins, Geological Society of America, Abstracts With Programs 29 (1997): A357.
2. See E. Hegner, and T. W. Vennemann, Role of Fluids in the Origin of Tertiary European Intra Plate Volcanism: Evidence From O, H, and Sr Isotopes in Melilitites, Geology 25 (1997): 1035-1038. Also, V. E. Camp and M. J. Roobol, New Geologic Maps Describing a Portion of the Arabian Continental Alkali Basalt Province, Kingdom of Saudi Arabia, Geological Society of America, Abstracts With Programs 23 (1991): 451; G. L. Hart, E. H. Christiansen, M.G. Best, and J. R. Bowman, Oxygen Isotope Investigation of the Indian Peak Volcanic Field, Southern Utah-Nevada: Magma Source Constraints for a Late Oligocene Caldera System, Geological Society of America, Abstracts With Programs 29 (1997): A87; and S.A. Nelson, Spatial and Geochemical Characteristics of Basaltic to Andesitic Magmas in the Mexican Volcanic Belt, Geological Society of America, Abstracts With Programs 29 (1997): A88.
3. W. A. Duffield and J. Ruiz, Contaminated Caps on Large Reservoirs of Silicic Magma, Geological Society of America, Abstracts With Programs 23 (1991): 397.
4. V. C. Krass, Magma Mixing as a Source for Pinatubo Sulfur, Geological Society of America, Abstracts With Programs 29 (1997): A164.
5. R. S. Harmon and K. Johnson, H-Isotope Systematics at Augustine Volcano, Alaska, Geological Society of America, Abstracts With Programs 29 (1997): A164. Also J. Dixon and D. Clague, Evolving Volcanoes and Degassing Styles in Hawaii, Geological Society of America, Abstracts With Programs 29 (1997): A191.
6. W. G. Cordey, ed., Volcanoes and earthquakes, Geology Today 11 (1995): 233-237.
7. G. B. Arehart, N. C. Sturchio, T. Fischer, and S. N. Williams, Chemical and Isotopic Composition of Fumaroles, Volcan Galeras, Colombia, Geological Society of America, Abstracts With Programs 25 (1993): A326.
8. Cordey, pp. 236-239. Also R. B. Smith, C. M. Meertens, A. R. Lowry, R. Palmer, and N. M. Ribe, The Yellowstone Hotspot: Evolution and Its Topographic, Deformation, and earthquake Signature, Geological Society of America, Abstracts With Programs 29 (1997): A166.