Earthquakes can devastate a city. They are a force of nature capable of destroying any structure. The Earth is made up of moving tectonic plates. Earthquakes occur along or near tectonic plate boundaries, where two plates meet. These plates are made of solid rock and sit on top of the mantle which is a layer of molten rock. This molten rock is constantly moving in a convection current. The Earth's core is what generates heat. The hottest rock moves away from the core and collides with the crust. Here it cools and then moves away from both sides. The now cooled rock falls back to take the place of the hotter rock that has risen, as shown in the diagram to the right. When rock pushes against the crust, it moves sideways. This moves the tectonic plates which float on top with the molten rock. When two different plates collide, they can cause violent shaking called earthquakes. Most of these tremors are very minor and happen all the time. They are so small that you can't feel them. The plates can also slide past each other, which can cause very minor micro-earthquakes. The plates slide about 10 millimeters per year, about the same rate as fingernails. When the plates don't slide enough, it can cause major problems. When the plates don't slide enough, it indicates that something is preventing them from sliding. When enough pressure builds, sliding restarts with a jerk. When this happens, it causes significant damage to towns or villages near the epicenter. The epicenter is directly above where the movements began. The place where the movements begin is called the focus. The devastation of a city depends on the size of the earthquake and the location of the epicenter. On April 18, 1906, one of the most devastating earthquakes in history struck...... middle of paper ......s shootings and looters had to be killed immediately. The children caught looting were spared but were publicly humiliated with a large sign placed over them. Around 10 p.m., the city had surrendered. There was nothing to do but watch. South Market was gone, the financial district was gone, and Chinatown would disappear into the night. In the morning, the residents were stunned. Their property, their homes and their entire lives were destroyed. There were ferries that transported people across the bay. Smoke was everywhere and a great silence reigned over the city. By midday on April 19, 250,000 people were homeless and more than 3,000 were dead. It was only the beginning and the city would burn for two more days. The costs were substantial. $235 million to $500 million, which in today's money would be between $4.8 billion and $10 billion. However, there were some positives to come from it?