Science

Earthquakes and fault lines Baney, Robert Hill, Heather SCI/245 4/24/2011 Scientists and geologists have a pretty good understanding of how the plates move and how this is related to earthquake activity. There are four different types of plate boundaries. First we have Divergent boundaries, where new crust is generated as the plates pull away from each other. Second we have Convergent boundaries and this is where the crust is destroyed as one plate is forced under another. Third we have the transform boundaries and this is where the crust is not created or destroyed as the plates slide horizontally past the other. Last we have Plate boundary zones where broad belts in which boundaries are not well defined and plate interactions are not clearly understood. The best known divergent boundaries is the mid-Atlantic Ridge, it is a submerged mountain range, which extends from the Arctic Ocean down South of Africa. This mountain range has been spreading apart for millions of years, which allows new magma to surface thus increasing the size of the mountains 2.5 centimeters each year. The two plates involved here are the American and the Eurasian plates and they are separating Iceland. The convergent boundaries are where the crust is being destroyed at about the same rate as it is being replaced in other areas of the world. These boundaries are long and deep trenches in the ocean and it are created by one plate being forced under another. These areas include the ring of fire which is a geographic region that has volcanoes that are active and are subject to earth quakes. Transform boundaries is a zone between two plates that are sliding horizontally past one another. Most of these areas we are discussing are found under the ocean. Because all these zones contain moving plates they tend to bump into one another or make contact. When this happens we have earthquakes, this is where friction builds up under immense pressure and then is released all at one time. Earthquakes can be measured and tracked all across the globe. When earthquakes happen under the water it creates a Tsunami. We use a seismograph to measure the force of earthquakes. The goal of the seismograph is to accurately record the motion of the ground during the activity. These interments are usually isolated and connected to the bedrock to prevent false readings and to make the results as accurate as possible. The Richter scale is a standard scale used to compare the power of quakes. This scale is the logarithmic scale meaning the numbers on the tool measure factors of 10. This means a number 5 on this scale has to be multiplied by ten to give you the power of the quake. A quake measuring less than 2.0, are known as a micro quake and happens constantly and is undetectable by humans. Moderate earthquakes measure above 2.0 and below 6.0, and quakes measuring above can cause significant damage. Earthquakes produce seismic wave, these can be placed into two main types of waves. First we have body waves and surface waves, body waves consist of p-waves or compression or longitudinal waves and s-waves shear or transverse waves. P-waves can travel through all types of matter, solid, gas, liquid, and s-waves can only travel through solid material. P-waves travel much faster than s-waves, P-waves are primary waves, s-waves are secondary waves, and then you have surface/Love waves, and they are produced when the stress ‘s from the tectonic plates are released. Primary waves or compression waves are fastest moving, travel in the same direction, and they travel faster through denser materials. Secondary waves or also known as shear waves, they travel slower, they travel to right angles to the vibration of the particles. S-waves cannot travel through liquids or gases; they travel faster through denser materials. Seismic waves are the main seismic wave types and are compression, shear, Rayleigh, and love waves and propagate outward in all directions. There are many areas of the world that are subject to these forces, and each earthquake is unique and different. Just the most recent large quake just hit Japan about a month ago. This event occurred off the coast and created a large Tsunami and devastating earth tremors that destroyed everything in its path. Earthquakes can’t be predicted and are an awesome force of nature. Coupled with other natural phenomenon’s these events can be devastating and reshape the earth as we know it. Our planet is changing everyday even if we can see or feel it. Other active areas include the Hawaiian Islands which where formed from volcanoes and new land is added each and every day.