Earthquakes

Earthquakes, one of mother natures most powerful forces. What are they and were do they occur from? Most of the famous mountains known today are a result of earthquakes. Well to be factual, they actually are formed from what's causing the earthquake to happen. To understand that though you need to understand the composition of our earth and what really is going on inside it. Knowing how we study Earthquake activity is what really puts everything together. Seismotology, which is the study of earthquakes and the waves they create has lead us to new understandings on how to determine when and were they are going to happen. You see, our Earths outer layer consists of the mantle, the MOHO and the crust. The Moho and the Crust are divided in to a dozen major plates and several minor ones. Some of which you probably heard," African, Nazca and the Pacific plate" are bigger than the others.

How is an earthquake created? Friction is always increasing as the mantle pushes and pulls the plates in all different directions. As these plates are being pulled, they're building up energy and tension, which sooner or later will be released. Although, what is causing the mantle to make the plates move? Under what is called the Lithosphere is the asthenosphere. The Athenosphere is made up of partially melted rock. This magma flows in what are called convection currents. When the currents heat up, it causes material to heat up and expand. As it expands it pushes the plates above it causing those plates to collide with others. When the current cools down it cause material to contract, in turn pulling the plates together causing a fault. An earthquake is then a result of these plate's movements.

Why do earthquakes happen? Movement of the oceanic against the continental crust as the two plates collide, one of them sub-ducts under the other causing lots and lots of tension. In the process of these to pushing against the other, the rigid face of the plates rub until a piece of one of them breaks off. Causing the plate to suddenly move and create what is known as an earthquake. The plates then snap back together. This is known as the Elastic rebound theory. There are other reasons for earthquakes besides one plate sub-ducting under another. There are also fault planes were you could have plates sliding against each other, and midplate earthquakes.

Where do these earthquakes happen? Most of the earthquakes occur along the edges of the continental and oceanic plates. Fifty percent of those are at sub-ducting zones concentrated along the Ring of Fire. Although plate boundaries are the most common spots for earthquakes, three of the most major Earthquakes did not occur at a plate boundary. They took place at a midplate boundary. It happened in New Madrid, Missouri. The fault there is made up three plate boundaries. Even though that class is not very important, the earthquake in New Madrid was very important because of the devastation it caused.

How are earthquakes studied? Scientists over the years have developed many precise tools to measure everything from their magnitude to their exact location. Richter scales are used to determine the magnitude given of from the sudden activity. The tool used to measure and record the waves is called a seismograph. Because the ground moves horizontally and vertically, there are different types of seismographs to measure the different motions. The waves emitted from the earthquake are what get measured. There are different types of waves, such as P waves, S waves, and L waves also known as love or Rayleigh waves. P waves are compressional back