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Welcome to San Francisco, one of the most beautiful and cultural cities in the world. But it wasn’t always that way. Imagine a time in the 1840’s when there were only a few hundred people that lived in what is now a metropolis. If you know about the gold rush, then you can probably guess why San Francisco became so important. Let’s take a look.

With the first words of gold came the most successful prospectors. These men, called the Forty-Niners, because of the year 1849, were able to gather gold at a rate of more than an ounce every hour.

However, the real money was being made by men like Sam Brannan who sold supplies to the Forty-Niners. And they did all of this selling in San Francisco. So you see, the men with dollar signs in their eyes would come to San Francisco to buy their supplies and then head out to the American River to strike it rich. Once they found their gold, they would come down from the hills to the new city of San Francisco looking for culture and fun. And when the gold started to run thin, the worn-out not so successful miners would return to San Francisco to settle down.

Gold became the driving force that brought people from all over the world to San Francisco. Because there were so many different kinds of people, San Francisco became a cultural mecca with a theater, opera and more newspapers than any city. The city became the envy of the world.

Earthquakes

Today, San Francisco remains a popular and beautiful city, but the same earth that once yielded gold is now a source of danger to its inhabitants. This is because it is so earthquake prone. An earthquake is the vibration, sometimes violent, of the Earth’s surface that follows a release of energy in the Earth’s crust (the crust is directly below the surface of the Earth). Most destructive quakes are caused by movement of the crust. The crust may first bend and then, when the stress exceeds the strength of the rocks, break and “snap” to a new position. In the process of breaking, vibrations called “seismic waves” are generated. These waves travel outward from the source of the earthquake along the surface and through the Earth at varying speeds. These vibrations cause the entire planet to quiver or ring like a bell or tuning fork. This is what we call an Earthquake.

Geologists have found that earthquakes tend to reoccur along faults which reflect zones of weakness in the Earth’s crust. Even if a fault zone has recently experienced an earthquake, there is no guarantee that all the stress has been relieved. Another earthquake could still occur. San Francisco lies along a number of fault lines.

The vibrations produced by earthquakes are detected, recorded, and measured by instruments call seismographs. The zig-zag line made by a seismograph, called a “seismogram,” reflects the changing intensity of the earthquake. From the data, scientists can determine when and where the earthquake took place.

The Richter Scale, named after Dr. Charles F. Richter of the California Institute of Technology, is the best known scale for measuring the magnitude of earthquakes. The scale is logarithmic so that a recording of 7, for example, indicates a disturbance with ground motion 10 times as large as a recording of 6. Earthquakes with a Richter value of 6 or more are commonly considered major; great earthquakes have magnitude of 8 or more on the Richter scale.