Among the most destructive natural phenomena caused by nature and known to man are earthquakes. Earthquakes are not only considered as one of the most destructive, but among the most frightening, traumatic and violent as well. In addition, earthquakes are beyond man’s control. They are also unpredictable. This paper aims to answer the following questions: How do earthquakes occur? What causes earthquakes? Based on its scientific definition, an earthquake is the result of a sudden movement of the earth’s crust due to the stress released from geologic faults or by volcanic activity.
Sometimes it is also called as seism or temblor (“Earthquakes”). We often think that an earthquake is merely the shaking of the ground based on what we experience and what we see in the news. What we are not really aware of is that an earthquake happens everyday. It is reported by the United States Geological Survey that over 3 million earthquakes occur yearly which means every 11 seconds, an earthquake takes place. That’s around 8,000 earthquakes a day. Most of the time, the majority of these quakes are and cannot be felt.
What alert us are the stronger earthquakes that happen in highly populated areas. In order to determine an earthquake’s strength, scientists measure earthquake strength by using a seismograph. The information gathered by the graph is then calculated. The unit of measuring an earthquake’s strength or ‘intensity’ is the Richter scale which is in turn used to rate the energy released by the quake which is known as the magnitude. When an earthquake occurs, it continuously produces waves referred as seismic wave. There are several types of seismic waves but the waves responsible in
the first few strikes of movement during an earthquake are called body waves. These waves often travel at the earth’s inner part (Harris, 2001). With the help of the P waves and the S waves, which are the types of body waves, scientists are able to determine where an earthquake took place. P waves also known as primary waves can travel through different mediums. It can travel through solids, liquids and even gases. It travels faster and hit the ground first. On the other hand the S waves or the secondary waves follows through making the ground also shake.
Apparently these waves helps scientist locate an earthquake’s epicentre of location. Through the help of seismographs, the amount of time between the P waves and the S waves are then recorded which is called seismogram, this will then determine how far away the earthquake was from the location. Most of the time it takes 3 seismographs to locate the epicenter or the exact direction of the earthquake which is called triangulation (Wald, 2008). During early times, natural causes were accounted with the anger of the gods that were displeased with mans action.
Today, natural disasters are no longer accounted to ancient gods anymore. Instead, man explains such occurrences based on modern science. There are many causes of earthquakes. These can be attributed to volcanic eruptions or even explosions created by humans but the most frequent potential cause of this is the seismic plate movement. The plate tectonic theory states that the surface layer of the earth called lithosphere is comprised of different plates. Through the advent of the plate tectonic theory, different phenomena and facts that were formerly unknown were finally understood.
Facts such as the movement of the continents and volcanic activities were just among the few facts that plate tectonics had unveiled. Since plates tend to slide on the region below the lithosphere, any of the three different things can happen at the boundaries between these huge plates: (1) the plates can move apart- whenever this occurs, hot, molten rock called magma, flows up. Magma will then appear on the surface, an activity that mostly happens on the ocean floor turning it into lava which in turn cools down and fills the gaps when it hardens.
The area where this occurs is called the divergent plate boundary. (2) The plates can push together- an occurrence where in one plate is pushed under the other one which is called subduction. When the plate is then pushed beneath, it melts down in the lower mantle layers. Although plates have the tendency to subduct with one another there are certain boundaries wherein neither of these two plates would be able to do so thus, the tendency of each plate is to push one another and form mountains. The convergent plate boundaries are an area where plates are more like to push against each other.
The plates would slide against each other- when this happens the plates are then pushed tightly together building a great tension in the transform boundary (Harris, 2001). We all know that earthquakes may occur anywhere and anytime but there are certain areas that are close enough where frequent actions of tremblors take place. The ring of fire is a zone where frequent earthquakes as well as volcanic eruptions occur. It is said that almost 90% of earthquakes in the world is experienced in this area.
Countries like the United States, Indonesia, Canada, Brazil, Colombia and Chile are some of the areas that are prone to tremblors (Crystal, 2008). An earthquake brings fear and devastation is alarming. Furthermore, the inability to predict an earthquake makes it even more fearful. Though scientists are still looking for ways to minimize the devastating effects of an earthquake, knowledge and the understanding earthquakes are man’s best defence. Earthquakes education serves as the best protection and the hopes and continuous researches provides more security and helps in devastation prevention.
References Earthquakes. The American Heritage Dictionary of the English Language, Fourth edition. Retrieved June 11, 2008, from http://dictionary. reference. com/browse/earthquakes Harris, T. (2001). How Earthquake Works. How Stuff Works. Retrieved June 12, 2008, from http://science. howstuffworks. com/earthquake. htm Wald, L. (2008). The Science of Earthquakes. U. S. Geological Survey. Retrieved June 12, 2008 from http://earthquake. usgs. gov/learning/kids/eqscience. php Crystal, E. (2008). Pacific Ring of Fire. Crystalinks. Retrieved June 12, 2008 from http://www. crystalinks. com/rof. html