Earthquakes can devastate a city. They are a force of nature that can destroy 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 solid rock and are found on the mantle which is a layer of molten rock. This molten rock constantly moves in a convection current. The core of the earth is what generates the heat. The hotter rock moves away from the core and presses against the crust. Here it cools and then moves away on both sides. The now cooled rock sinks to take the place of the hotter rock that has risen as shown in the diagram to the right. When the rock presses against the crust it moves laterally. This shifts the tectonic plates that float on the surface along with the molten rock. When two different plates collide they can cause violent tremors called earthquakes. Most of these tremors are very mild and occur continuously. They are so small that we cannot feel them. Plates can also slide past each other causing very minor microearthquakes. The plates slide about 10 millimeters per year, about the speed of fingernails. When the plates don't slide enough they can cause big problems. When the plates don't slide enough it means that something is preventing the plates from sliding. When enough pressure builds up, it will start sliding again with a jolt. When this happens, it causes severe damage to any city or town near the epicenter. The epicenter is directly above where the movements began. The point 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 of the shootings and looters had to be killed immediately. Children caught looting were spared but were publicly humiliated with a large sign placed over them. By 10pm the city had surrendered. There was nothing to do but watch. The South Market was no more, the financial district was no more, and China Town would disappear at night. In the morning the residents were stunned. Their possessions, homes and their entire lives had been destroyed. There were ferries taking people across the bay. Smoke was everywhere and there was a great silence over the city. By midday on April 19, 250,000 were homeless and over 3,000 were dead. This was just the beginning and the city would burn for two more days. The costs were considerable. $235 - $500 million dollars, which in today's money would be about $4.8 - $10 billion dollars. However, there were some positives that came from itPositives?