The theory of plate tectonics explains what happens at plate boundaries. According to this theory, there are three primary plate boundary conditions; divergent, convergent, and transform boundaries. Divergent plate boundaries are characterized by ocean ridges and sea floor spreading; volcanoes are the most obvious setting. Here, a new crust is generated because the plates pull away from each other. Convergent plate boundaries are characterized by trenches and island arcs. In this setting, the crust is consumed in the Earth’s interior as one of the plates dives under another. In the case of transform plate boundaries, the crust is neither produced nor destroyed, as plates horizontally slide past each other. Significant earthquakes can occur under all of these boundary conditions.

We typically associate Japan with earthquakes because we know that it is a very earthquake prone island. The state of Alaska in the United States is also earthquake prone. The total number of earthquakes in Alaska per year is greater than the total number of earthquakes in the rest of the United States. The examples of Japan and Alaska reveal that more earthquakes occur at locations close to the plate boundaries. On a global scale, Japan, the Philippines, Indonesia, Chile, and western United States, are located along the so-called “Pacific Ring of Fire,” where about 90% of the world’s earthquakes and 80% of the world’s largest earthquakes occur.

The magnitude of an earthquake is a representation of the total amount of energy released by the event. Typically, it is measured using the recorded ground oscillations from a seismogram. However, the interpretation of the magnitude is not straightforward because the magnitude scale is logarithmic. For instance, a magnitude 7.0 earthquake produces approximately 10 times more ground motion and releases about 32 times more energy compared to a magnitude 6.0 earthquake (2).

According to the statistics published by the US Geological Survey, every year on average 134 earthquakes with magnitudes 6.0 to 6.9 occur worldwide, 17 earthquakes with magnitudes 7.0 to 7.9, and at least one large earthquake with a magnitude greater than 8 (Figure 3). Further, the number of earthquakes of magnitude 7.0 or greater has remained fairly constant but the number of moderate earthquakes (i.e., 6.0 or less) appears to be increasing. According to experts at the US Geological Survey, a partial explanation may lie in the fact that there is a tremendous increase in the number of seismograph stations in the world over the last twenty year. Thus, the actual number of earthquakes has not increased, but our ability to detect them. In scientific terms, this is referred to as reporting bias (3). When it comes to myths about earthquake activity related to weather and time, scientists rejects any connection. Earthquakes occur whether it is warm or windy, early in the morning or late at night.

In the United States, earthquakes are one of the most significant natural hazard for around 75 million Americans living in 39 states, including the state of California where the majority of the state’s population lives within 32 km of active faults. Historically, the region has been very active (Figure 4). To help predict earthquakes in California, a multidisciplinary group of scientists and engineers from various disciplines established a team entitled Working Group on California Earthquake Probabilities (WGCEP). The team had a very ambitious objective to develop a comprehensive earthquake rupture forecast model for the state of California using the best available science. The details of the sophisticated model are beyond the scope of this essay, but the recently released report (USGS Open File Report 2007-1437) is available for public access (5). In her essay entitled, “The big one is evitable. Catastrophe is not,” Cathleen Decker, an editor of the Los Angeles Times, refers to the future predictions presented in the report as a “Chilling look into the future” (7). Based on historical evidence and scientific data, it is almost certain (with a 99% chance) that there will be at least one earthquake with magnitude 6.7 or greater in the state of California within the next thirty years. The likelihood of a more significant earthquake (magnitude 7.5 or greater) within the next thirty years in California is 46%. In the Greater Bay Area specifically (area includes large cities such as San Francisco, San Jose, Oakland), the probability of at least one earthquake with magnitude 6.7 or greater within the next thirty years is about 67% (6).

The current state of science considerably reduces the risk of death and damage by making resources available to individuals, teachers, policy makers, and engineers, but unfortunately, science at this time can neither prevent nor predict the exact time when an earthquake will occur. Casualties, financial losses, and mental trauma are sometimes inevitable for earthquake victims. Social and emotional suffering are often not limited to actual victims, but to everyone who has access to the news. Unlike financial and material losses, the psychological consequences of an earthquake exposure are long lasting. To address these consequences, earthquake preparedness should include mental and social aspects of the disaster as well.

Reference

• This dynamic Earth The Story of Plate Tectonics by W. Jasquelyne Kious and Robert I. Tilling (Online edition) U.S. Department of the Interior, U.S. Geological Survey http://pubs.usgs.gov/publications/text/Vigil.html
• USGS Earthquake Hazard Program – Earthquake Facts and Statistics http://earthquake.usgs.gov/earthquakes/eqarchives/year/eqstats.php
• USGS Earthquake Hazard Program – Are Earthquakes Really on the Increase? http://earthquake.usgs.gov/learn/topics/increase_in_earthquakes.php
• California Geological Survey – Probabilistic Seismic Hazards Assessment – Historic Earthquakes http://www.conservation.ca.gov/cgs/rghm/psha/Pages/historic.aspx
• The Uniform California Earthquake Rupture Forecast, Version 2 (UCERF 2) By 2007 Working Group on California Earthquake Probabilities, 2008 http://pubs.usgs.gov/of/2007/1437/
• USGS Earthquake Hazard Program – 2008 Bay Area Earthquake Probabilities http://earthquake.usgs.gov/regional/nca/ucerf/
• Los Angeles Times (January 17, 2010) http://www.latimes.com/news/local/la-me-week17-2010jan17,0,4714976.story

Around 4–5 billion years ago (bya) my formation began from the remaining matter after the creation of the sun. In time, this matter accumulated and formed the small planetary objects (planetesimals) which were the earlier forms of future’s giant planets. Our collisions continued with the planetesimals that orbited the sun. As a result of these continuous collisions and bombardments, my surface temperature raised to almost 6,000oC. What I am trying to say is that I was an enormous globe consisting mainly of metallic substances that were melted in boiling lava and showered by thousands of meteoroids and comets. God the Creator has hidden many messages of mystery regarding the entire process I endeavored for humans to discover.

When I began to cool down, my surface hardened like a shell, and because I was not yet sufficiently protected by the gaseous shield known to us today as the atmosphere, my shell was destroyed by the ceaseless continuation of the meteoroid bombardment as soon as it began to form. This transformation continued for billions of years. At last when the invasion of the meteoroids began to ease, I started to mature and slowly began the process of cooling down.

4.4 billion years ago

The creation of pieces of land that looked somewhat different than the seven continents at the present began. They were just sections of land floating on my coat of crust. The formation of crust around my surface was subjected to rupture due to the high pressure caused by the intense heat deep down inside me. Over a period of time this crust, which separated into a number of huge fragments (plates), experienced various deformations that resulted in the formation of mountains. This is how the basins of the ocean and the contours of the continents began to emerge. This was the period during which new specimens of rock (granite) and the floor of the ocean (basaltic), consisting of rising magma, formed the core of the continents. Today scientists are studying the oldest granites (billions of years old) that have managed to survive natural disasters and destruction to discover how the first continents were actually formed.

Granite is the rock that forms the cores of the continents (cratons). Cratons are produced by the primary component of the oldest crust. Cratons are light enough to float on my coat of crust; they are a system created in a way that enables the development of continents. These cratons are found especially in central parts of Africa and also in South America, Australia, North America, and Scandinavia.

My surface is made up of integrated fragments called tectonic plates. Even though my crust was created by rock, it was created flexible enough to allow the plates to move a few centimeters every year caused by the intense heat from beneath my surface.

Continents

Ground movement and various changes have occurred over time due to the dynamic structure of the continents and plates attached to the mantle. Discoveries of exactly the same fossils and identical fresh water organisms in two completely different continents far from each other have proved this. The actual reason for the plate’s activity is that my core is much higher in temperature than my surface. The core deep inside me is around 5,500oC. The greater portion of this intense heat occurred in my early days as a result of the collisions and bombardments I faced, and the remaining is related to the disintegration of the radioactive elements which settled particularly in my mantle section. The heat waves which spread from my core were passed on to the next layer of the mantle. The heat melted a section of my mantle layer and magma forced my molten rocks to the surface. The molten rock, which fills the spaces between the cracked plates, enables new rock to develop, and then the plates separate from one another.

Around the same period of the formation of new rocks, my plates and the continents found on them separated. The formation of rocks deep within ocean continues the creation of the range of volcanic mountains even today. The range of under-water mountains continues for about 12,000 miles between the Antarctic and the North Pole and rises above sea level in some places.

The region called Iceland between the North American and Eurasian plates was formed as a result of an enormous volcanic eruption. This is one of the few places where the separation of the continents is clearly visible. The crevasse of Iceland, surrounded by the American plates on one side and the other European plates on the other, is around 3 miles in width. This crevasse is increasing with the formation of new rocks and is expanding the distance between America and Europe. Scientists say that the distance between the continents is increasing by around 1 inch every year, so within a hundred years the distance between America and Europe is expected to increase another 8 feet.

3.4 billion years ago

The main continents were forced together by movement of the tectonic plates forming new continents, and there are still remaining pieces of these continents inside the cratons of Australia and Africa.

2.7 billion years ago

My first super continent is still the ruling territory. But due to the power built up by heat emerging from my core, the tectonic plates are on the verge of separating this continent. Because of the heat from my core, the main land has separated and oceans were formed in my surface. Today these oceans do not exist on my surface anymore; but you can still find their pieces in the continents by a careful look.

1.1 billion years ago

The supercontinent called Rodinia, a continent which contains most of the earth’s landmass, was created. Seven hundred and fifty million years ago (mya), the heat from my core began to break down this supercontinent, and as a result Rodinia was destroyed and a new supercontinent called Pangaea, the origin of all the continents known in the present day, was created.

Two hundred million years later (or five hundred and sixty-five mya): I became acquainted with bacteria, funguses, poriferans (sponges), earthworms, mollusks, segmented worms, and arthropods.

During the time when these creatures lived on me, the climate was moderate. Major volcanic activities occurred during this period when most of the land was covered by shallow seas. The sudden outbreak of the thousands of species of living creatures during this period may seem amazing to you; in fact, this was actually the first period in which complex structural vertebrates were created.

495–435 million years ago

I first became associated with the red and green sea algae. This was also the period in which various fish and sea creatures were created. The enormous landmass of this period called Pangaea gave me a totally different appearance and had a huge impact on the climate. The reason for this was that a large section of the land was so distant from the sea. The climate of the inland regions was showing deep scale signs of change with every season-certain periods of the year were very hot and others considerably cold. During this time, the ocean did not have the effect on the climate like it does today. This is why the climates varied to such an extent. The change of climate played a huge role in the extinction of many species of that period and destroyed almost 90% of the living creatures.

Creation has continued at a distinct magnitude during the millions of years that have passed, and between 270–340 mya larger proportioned variations of vegetation were created. In a short space of time, this vegetation formed into giant trees that covered huge areas of land. The largest deposits of coal were created from the fossilization of these trees, an example of creation that would make your life a little easier in the years to follow.

On the other hand, the territories began to gather together close to the planes of the equator, and this vast land was covered with rain forests resembling the Amazon. These immense lands of greenery were the marshy forests that were home to extinct ferns and the first seeds of the various groups of plant life. The inhabitants of this intense vegetation were mainly insects, centipedes, and scorpions, but much larger than the ones we know today. The plants and forests disappeared suddenly at the end of this period, and towards the end of the same period when the vast lands of Pangaea began to take form, the glaciers expanded, the sea water receded, and the arid climate changed dramatically along with the forestry structure and vegetation. Then the creation of many new creatures occurred.

250 million years ago

The supercontinent Pangaea began to break up, and this separation caused the formation of Gondwana in the northern hemisphere and Eurasia in the south. Throughout the millions of years, South America began to recede from Africa while North America receded from Europe, resulting in the formation of the continents as we know them today. Australia drifted from the Antarctic continent and moved slowly towards more moderate climates. The evolution of the continents continued to form the huge canyons and valleys in America, and the vast range of mountains, including the Himalayas and the Alps. Between 225–190 mya mammals were created, and between 190–135 mya, birds and alga were created, followed in the next period by plantation seeds which almost completed my preparation as a suitable place for you all to live.

100 million years ago

The plan of the present day continents became apparent. Sometimes my land masses would collide in the regions where the plates joined and caused activity like the formation of the mountains. Without this plate movement, there would have been no mountains created on the planet. During this period, the various species of dinosaurs and reptiles became extinct for reasons unknown to humans. Throughout the following 100 million years, the creation of the most significant mountain ranges, like the Himalayas, occurred along with the continuing collisions of the continents. These plates continue to move 5–10 cm every year and still cause collisions today.

Today I am the proud owner of seven continents. Africa-Eurasia is an enormous supercontinent which houses Africa, Europe, and Asia. Beginning from the plateau of Siberia in Russia, it reaches as far as Africa, but Africa-Eurasia is not my only supercontinent. North and South America joined by Panama also have vast territories. If the Bering Strait that separates Russia and Alaska were to freeze, a person who set out from South America could walk as far as South Africa covering a total distance of 25,000 miles.

Although you are may not realize it, the activity of the continents continues today, and my existence that began billions of years ago will continue in the future until the time comes for me to die (you call this doomsday).

There is another aspect of the continental activity that affects you. This occurs in the form of disasters, for instance the earthquake, an event of nature which has occurred for millions of years. This activity of creation occurs as a result of the intersection of the plates, the collision of continents, or the ocean plates submerging beneath the continent. The tsunami disaster in Indonesia in 2004 was the result of a catastrophic movement of these plates.

The exceptionally lengthy process of my creation explains the transformations and progress I have experienced until I reached the condition suitable for the most precious and honorable of all creation: human beings. I hope that every moment and every aspect of the manifestation of science, wisdom, power, and willpower of my life story and creation will be a guide for you in the future and will encourage you to be even more curious about my end and to bow to our Almighty creator in respect of all He created.