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Know and Understand Natural Disasters 

A natural disaster is when events such as earthquakes, mudslides, floods or wildfires affect people. Despite our inability to control these events, we can plan and prepare for them to minimize damage when they do happen. Below are brief explanations of disasters that are common in California. Follow the links to more information about a specific disaster.


An earthquake is a sudden shift or movement of the plates in the earth’s crust. On the surface, this moves and shakes the ground and can be very damaging to poorly built structures. The most powerful earthquakes can destroy even the best built structures. They can also cause other disasters, such as tsunamis and volcanic eruptions. Earthquakes occur along fault lines and are unpredictable. California is highly prone to earthquakes because of its many active fault lines.


A flood is a natural disaster caused by too much rain or water in an area, and could be caused by many different conditions. In California, floods are most often caused by prolonged rainfall from a storm. Flooding is particularly dangerous because it often leads to landslides or mudslides.


A wildfire is a natural disaster that starts in forests, deserts with heavy brush or other vegetated areas. They can be a great danger to people who live in or near such areas. Wildfires can be started by lightning, extremely dry vegetation in warm climates, human carelessness or intentionally. In the wilderness they can quickly burn thousands of square miles. In metropolitan cities such as Los Angeles, they can burn entire neighborhoods. Southern California is very prone to wildfires because of low annual rainfall, warm summers and dry vegetation.

Landslides and Mudslides

A landslide occurs when soil, rocks, trees, parts of houses and other debris is swept downhill. Landslides can be cause by earthquakes, rain or general instability of the land. Mudslides are a special type of landslide, in which heavy rainfall causes loose soil on steep land to collapse and slide down. Mudslides occur with some regularity in parts of California after periods of heavy rain.


A tsunami is a series of waves that happens when water in a lake or sea is quickly displaced on a large scale. Disturbances such as earthquakes, volcanic eruptions, landslides or meteorite impacts can cause tsunamis. Because the most common cause is an undersea earthquake, there is potential for coastal areas in California to be impacted by a tsunami. According to researchers at the University of Southern California, a 7.6 magnitude earthquake under the seafloor near Catalina Island could cause a tsunami to hit the Southern California coast.

Power Outages

A power outage is the loss of electricity to an area. A power outage may be referred to as a blackout if power is lost completely, or as a brownout if some power supply is still present. Blackouts and brownouts are common in California because of extremely dense populations. Though power outages are not necessarily considered natural disasters, they often occur with natural disasters. Power outages are very damaging for hospitals, since many life-supporting medical devices and tasks require power. For this reason, hospitals have emergency power generators which are typically powered by diesel fuel and start automatically when the power goes out.

Extreme Heat

Heat-related illness can be very dangerous and affect anyone when temperatures outside get hot enough. The best defense against heat-related illness is prevention. Drinking more fluids (non-alcoholic and without caffeine or sugar) can help prevent heat-related illness regardless of activity level. Taking cool showers or baths, wearing loose and light-colored clothing and limiting outdoor activity to cooler times of the day can also prevent illness. Infants and young children, people aged 65 and over, mentally ill and physically ill people are at a greater risk for heat-related illness and should be checked on frequently.

Climate Change and Health Equity

For more information please visit the climate change and health equity page with the link above.

For more information on natural disasters visit the Centers for Disease Control and Prevention.

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