A natural disaster can be defined in a few different ways.  In it simplest terms, it is a weather or other natural event that has a destructive or significant effect on land, property and people. One example is a volcano. But natural disasters do not include all serious weather events. A blizzard or terrible windy snowstorm, although a serious occurrence, is not actually a natural disaster.  Try to think of natural disasters as those weather events that are the rarest and (sometimes) destructive.  Here is a list of a few important natural disasters, and what they are capable of doing.

Earthquakes – Earthquakes are caused by movement or shifting of the outer crust of the earth. This crust moves, shifts, vibrates and breaks into different pieces during an earthquake. The earth is made up of three areas: the inner core, the soft middle layer, and the outer core.  In an earthquake, built up pressure in the earth crust is released outward, and causes the outer crust to shake. The center of this release is usually through something called a “fault.” One such fault is located in California; it is called the San Andreas fault. This is why California is more likely to have earthquakes than other parts of the country.

Earthquakes, which cause the ground to move and shake, are often so strong that many buildings crumble to the ground. They are measured on a scale called the “Richter scale,” which measures the strength of an earthquake. The scale is measured by magnitude, and goes from 1-9.  An earthquake with a magnitude of one is a very minor incident, and no one actually feels it. A magnitude 5 earthquake is usually felt, but causes very little damage. A magnitude 7 earthquake is a major event, causing structure damage and loss of life up to 60 miles from the center (both of San Francisco’s major earthquakes of the last 100 years were high on the magnitude 7 scale). Finally there are magnitude 8 and 9 earthquakes. These are both extremely rare, but have occurred.  They can cause damage well over 100 miles in radius from the center, and when in major populated areas, can be a threat to human life.

Unfortunately it is difficult to predict earthquakes, but scientists are always working on this problem. The good news is that major earthquakes are pretty rare. And these days, buildings are constructed with earthquakes in mind, so that less damage will be caused if there ever is an earthquake.
 
Hurricanes – Hurricanes are severe tropical storms that are characterized by strong winds.  A hurricane is a fast moving, swirling windstorm that usually comes with torrential rains and lighting. They generally originate in the South Atlantic Ocean in the Caribbean Sea or Gulf of Mexico. Hurricanes are huge, and rotate around an area called the “eye.” Each year, about two hurricanes reach the American coastline, causing severe damage.  The wind and rain can damage buildings, cause ocean waves and flooding, and even injure the natural environment.

Each year there is a hurricane “season” in the southwest, and the Weather Service names each hurricane.  Hurricane names are in alphabetical order, switching between male and female names for each hurricane. For example, the first four hurricanes of a season might be called Andrew, Brittany, Christopher, Deborah and so on.  
 
Hurricanes are divided into five categories based on their strength.  Category 1 – winds of 74mph – 95mph, Category 2 – 96mph – 110mph, Category 3 – 111mph – 130mph, Category 4 – 131mph – 155mph, and Category 5 – over 155mph.  These storms feed off of warm tropical waters, and usually travel in a northerly direction. As they head north into colder waters and over land, they slowly begin to loose intensity. Since most hurricanes fall below the 74mph-wind limit by the time they reach land, they are then downgraded to tropical storms. However, every now and then the storm will be so strong, that even after loosing intensity, it is still a category 3 or 4 hurricane by the time it hits land. This is the most devastating type of hurricane. Fortunately, hurricanes are extremely predictable. As a result, many people are prepared and seek proper cover by the time the storm arrives, helping to limit the amount of damage.

Tornadoes – A tornado is a violently swirling column of air that stretches from the cumulus cloud in the sky all the way to the ground. It is literally a small cyclone and usually only lasts for a few minutes. Tornadoes are often accompanied by torrential rains, thunder, and lighting. The storms are basically an extreme form of the typical thunderstorm. Although the wind in tornadoes is usually around 110 miles per hour, strong winds can reach speeds as high as 300 mph – that’s faster than any race car! Tornadoes are dangerous because they move along the surface of the earth traveling an average distance of five to six miles. Sometimes, though, tornadoes can reach as far as twenty miles along the earth’s surface. Their speed is notable, often traveling faster than 50 mph, and able to outpace cars with speeds up to 70mph. Usually though, tornadoes travel at slower speeds around 20 – 30 mph. 

Although tornadoes don’t last long, their power can be amazing. Houses that are hit directly are almost always destroyed, and tornadoes have been known to pick up 18 – wheeler trucks and throw them hundreds of feet through the air. Luckily, it is very easy protect people from tornadoes. Because tornadoes always generate out of severe thunderstorms, they are fairly easy to predict. So, with enough warning, many people are able to seek cover before the tornado arrives. Houses in areas that often get tornadoes often have storm shelters or cellars, as it is safer to be underground.

These are the three most important and common natural disasters in America, however, many other parts of the world experience many other different types of natural disasters.