Earthquake Design

Earthquake Design

Geology is the study of the earth's landmasses. The earth is constantly changing. These changes are to slow for one person to see in his or her lifetime. Forces cause different things to happen on the surface of the earth. Such as mountains growing and eroding. The earth is broken down into layers lithosphere, hydrosphere, and atmosphere. The lithosphere is the dense, solid layer that surrounds they earth. Which we call the ground. Scientists believe that the earth was formed by very dense elements such as iron and nickel. Which are in the core of the earth. The earth crust covers the mantle. The crust is made up of over two thousand different compounds called minerals. The crust is the outer most, thinnest layer. It ranges between four and seven kilometers. The mantel is sits right below the crust and is about two thousand nine hundred kilometers. As you go deeper into the mantel is becomes hotter and more pressure. The upper part of the mantel and the crust make up the lithosphere. There are major plates that sit on top of the earth's mantle. These plates are very large rigid slabs of crustal rock that float on top of the mantel. The lighter plates carry the most landmass and the more dense plates carry less landmass. These plates are like large sheets of ice siting on top of a pond. Like the ice they do not sit still. Scientist do not know what moves these plates but we do know they move. There are nine major plates. These plates have boundaries. There are the types of boundaries. A divergent boundary is when two plates move apart from one another. A convergent boundary is when two plates move towards each other. A transform boundary is when two plates slide horizontally past each other. These boundries are also called faults.

Most earthquakes are caused by the sudden slip along geologic faults. The faults slip because of movement of the earth's tectonic plates. This concept is called the elastic rebound theory. The rocky tectonic plates move very slowly, floating on top of a weaker rocky layer. As the plates collide with each other or slide past each other, pressure builds up within the rocky crust. Earthquakes occur when pressure within the crust increases slowly over hundreds of years and finally exceeds the strength of the rocks. Earthquakes also occur when human activities, such as the filling of reservoirs, increase stress in the earth's crust.