Earth Science Themed Essays
When I was in the first grade a man living in California predicted that there would be an earthquake along the new Madrid fault line and that this earthquake would be major and could occur at any time in the near future. Many people living in my town remembered or had heard stories from their relatives about the three earthquakes that hit the Mississippi Valley in the winter of 1811-1812. The fear of the accuracy of the prediction and the possible consequences of such an earthquake led our school district to initiate a program of earthquake awareness. Special bells at school were sounded as a signal for students to drop under the tables and desks as fast as possible. We practiced getting off of buses and standing in doorways. We also took home information sheets with facts on how to prepare for an earthquake at home and the supplies needed for survival should a disaster occur. Of course, the earthquake did not happen, and the man from California died in obscurity. But it fostered within me a fascination and fear of earthquakes that I still have to this day.
History of Earthquakes
An earthquake is the sudden shaking, or shock movement, of Earth's surface caused by the extreme release of energy deep within Earth's crust. Almost all movement occurs along pre-existing breaks in Earth. There are numerous faults that occur on Earth's surface, and most of them remain quiet, while other faults are in a continuous state of movement and account for the more than 100,000 recorded quakes that occur during a year. According to the theory of plate tectonics, Earth's crust is made up of several rigid plates that are in continuous motion every day. Movement along already established breaks in Earth's crust, otherwise known as geologic faults, causes earthquakes. It is known that the underlying forces that cause movement along the faults do not operate in the same violent and convulsive fashion as the earthquakes themselves. These underlying forces are always moving and bending the sheets of rocks that lie on each side of the fault, storing up energy. Suddenly, the force causes the rock along the fault line to break, move, and the two parts to slip by each other.
Earth movements, created by earthquakes, create four kinds of waves. The L waves are long waves with a low frequency that move along the surface of Earth's crust. These are the waves that cause the most destruction to human lives and property. The R waves also move along the surface and travel in a vertical plane in the direction of the transmission. Both P and S waves travel through the Earth. Compression waves, or P-waves, travel through both solids and liquids. The P waves oscillate to and fro in the direction of transmission, and the S waves move at right angles to the transmission. Shear waves, or S waves, travel only through solids. After an earthquake, the shock waves can be detected on the opposite side of the globe, the compression waves arriving in about 22 minutes. P and S waves travel away from the quake in large circles that gradually get bigger as they pass through the Earth. All four types of waves are strongest the closer they are to the center of the earthquake.
The study of the waves and the velocity of their travel is called seismology and helps scientists to discover the type and density of rock to be found in certain areas and in certain levels of Earth. The crust, mantle, and core are easier to define and label in any one certain area after the waves are recorded and studied.
New Madrid Fault Line
On December 16, 1811, the greatest recorded earthquake to hit the continental United States occurred in a small town called New Madrid, Missouri, along the banks of the Mississippi River. New Madrid, with a population of less than a thousand people, was totally destroyed. The ground moved like waves in the ocean, and dust filtered through the air and darkened the sky. Trees tilted into each other, linked branches, and were then torn apart when the trunks settled back into the soil. Great cracks opened in the soil, and huge waves in the river capsized and sank many boats and barges. Sandbars and entire islands disappeared, and the topsoil of many farms totally disappeared underground. The Great New Madrid Earthquake of 1811-1812, as this period of history is now called, happened over a three month period with three main shocks or earthquakes. According to historic records, the shocks were estimated to be more than a magnitude 8.0, or maximum intensity. When the first aftershocks had died down, another shock struck on January 23, 1812. After two more weeks of relative quiet, the last shock was felt on February 7, 1812. The Mississippi River changed course and, some said, flowed backward for days. Two large lakes, including Reelfoot in Tennessee, were formed in dropped basins. The entire fault zone is believed to have ripped apart in this series of earthquakes, and aftershocks were felt in the immediate vicinity over a year later.
The shocks were felt from Chicago and Detroit to Washington, D.C., and Boston. The entire eastern part of the country suffered with aftershocks for as long as two years after the initial quakes. Because this took place in the nineteenth century, transportation and communication were extremely primitive. It took days for the news of these earthquakes and their severity to reach all parts of the United States. The United States was too young and poor to attempt any in-depth study. Amateur scientists visited the site, but the sparseness of the population and the looming War of 1812 caused the entire nation to quickly turn its attention to more pressing problems. The damage that could have occurred if this area had been more populated was averted by the newness of the country.
This system is a series of faults beneath the continental crust in a weak spot known as the Reelfoot Rift. Of course it cannot be seen from the surface of the Earth. The fault extends 150 miles southward from Cairo, Illinois, to Dyersburg, Tennessee. The past 20 years have shown scientists that the New Madrid fault affects a much larger area than the California zone. The differences in geology between the land east and west of the Rockies are significant and indicate the need for quick action should an earthquake occur. The loss of life and destruction of buildings only prove how much more careful we need to be about where we live and how we live. So why exactly do we still go back to rebuild after such great destruction, which could happen again in the same place?
Today, the Mississippi Valley is home to millions of people, including those in the cities of St. Louis, Missouri, and Memphis, Tennessee. This adds to the danger of destruction because most structures are not built to withstand the severe shaking of an earthquake. The Mississippi River attracts people because it is the lifeline of commerce connecting the northern part of the United States to the Gulf Coast. It is also the intersection of major highways that connect the East Coast to the West Coast. The rich farmland, beautiful wooded areas, and mountainous tourist attractions have also encouraged people to settle in these areas or spend their vacations here.
Recent research indicates that most major earthquakes occur every 600 years. Unfortunately, the chance of a major earthquake hitting the New Madrid fault line rises 7 percent for every 50 years that passes. And of course, nature does not always follow the rule of averages. Tremors are recorded daily in the Memphis and St. Louis area and elsewhere in the Mississippi Valley frequently. Earthquakes can strike suddenly and with no warning, and because the most devastating earthquake in this nation's history occurred along the New Madrid fault line, a sense of false security could be the worst thing the people in this area could assume. The next great earthquake will tax the economy and resources of the Central Mississippi Valley region. And because this area has a substantial amount of the nation's manufacturing facilities and one-third of the nation's population, a major earthquake could place the nation at risk. As power is lost, services disappear, and the population has to learn to survive on their wits and what the land can provide.
The development of long- and short-term prediction of earthquakes is moving forward with the increase in scientific study, the ability to study past earthquake cycles, the use of models, and better instrumentation. The ability to assess construction costs as opposed to the potential for the saving of lives has become a scientific process. Unfortunately, most of the buildings in the New Madrid fault line were not built to withstand the shaking caused by earthquakes. The modern city of Memphis has been built along a bluff on the Mississippi River. The Autozone corporate headquarters located in Memphis is the first building to be built to possibly survive the waves of an earthquake. Many organizations have banded together with state and national government to implement plans of action for the reduction in the loss of life and property damage along this fault. These include the following:
No matter how many scientific instruments are created to predict the possibility of a future disaster, you cannot prevent earthquakes. An extensive program to reduce the vulnerability of society to destructive earthquakes must be created with the ability to forecast if an area is prone to disaster and what precautions should be taken. Plans and people must be in place for quick aid and recovery to an area that is struck by an earthquake. This includes the alteration of existing structures to improve their performance in the event of an earthquake. Even if structures could withstand the ground shaking, there is the added hazard of foundation failure causing buildings to topple over due to the ground giving way underneath them. When nature or man-made disasters destroy cities, they are almost always rebuilt, for the exact same reason, in the exact same place. Most often cities are built in areas for their climate, economic importance, strategic defense, and recreational facilities. However, not taking all of the danger factors into consideration before planning a city or town increases the hazards of fire and flooding, which are very likely in earthquake-prone cities.
"Center for Earthquake Research and Information at the University of Memphis." University of Memphis. 18 February 1999. http://www.ceri.memphis.edu
Erickson, Jon. Volcanoes and Earthquakes. Tab Books Inc. Blue Ridge Summit, Pennsylvania, 1998.
Lanham, Urless Norton. The Sapphire Planet. New York: Columbia University Press, 1978.
Lee, Chris Eckstrom. Our Awesome Earth. Washington: Special Publications Division, National Geographic Society, 1994.
Pellant, Chris. Earthscope. London: Tiger Books International, 1985.
Penick, Jr., James Lal. The New Madrid Earthquake. Columbia, Missouri: University of Missouri Press, 1981.
World Book Encyclopedia. Volume 6. World Book Inc. 1990, USA. Pg. 33.
USGS. "Information on Earthquakes." 23 June 1998 http://easternweb.er.usgs.gov/eastern/earthquakes/faq5a.html
This winning entry in the museum's Young Naturalist Awards 1999 takes a look at the earthquakes and California's Madrid Fault Line. Maribeth's narrative essay covers:
Less than 1 period
Supplement a study of Earth science with an activity drawn from this winning student essay.