California’s Natural Hazards Volcanoes, Landslides, and Floods Presenters: Steven, Bryan, and Leo

What causes a volcanic eruption? Earthquake triggers eruption Pressure pushes magma up chamber Volcano has an eruption

Where Are Active Or Potentially Active Volcanoes? 5 potentially ( possibility ) active volcanoes Medicine Lake – Last activity 900 years ago Mount Shasta - 1786 Clear Lake – 10,000 years ago Lassen Peak - 1921 Long Valley – 1750’s Coso – 2.5 million years ago

What Can We Do To Help Prevent or Prepare For Eruptions? Seismic activity near volcanoes means, might have an eruption Get breathing masks and goggles Get out of the volcanoes area

http://www.youtube.com/watch?v=OowFvnlWI90

floods A flood is the submerging ( to put underwater ) with water of a normally dry area. Floods are caused by many things, including rainstorms, slow water run-off, earthquakes, broken dams, underwater volcanic eruptions and tsunamis, or hurricanes.

Cause of flooding   floods are a natural consequence of stream flow in a continually changing environment caused by precipitation, which is caused by weather For example, heavy snow melts, water saturated ( unable to absorb or dissolve ) ground, unusually high tides, and drainage modifications ( to change ) when combined with heavy rain can lead to flooding

Areas prone to floods Next to rivers Where there is bad weather Areas below sea level

Flash flood Natural weather disaster Most dangerous flood power of a flood with incredible speed and unpredictability. Dams and levees brake

Definition: Movement of slope Important Factor: Gravity Landslides Definition: A Landslide is a process that results from the downward or outward movement of slope forming materials including: rock, soil, artificial fill or a combination of these. . Landslides are a form of mass movement, a term used to describe any sort of gravity-induced movement of sediment down a slope. Mass movements can occur slowly over a period of years, or they can happen in a matter of minutes. With any mass movement, a soil layer is separated to some degree from the underlying bedrock. Main Cause of Landslide: When gravity overcomes the source of friction. Gravity will pull the soil or rocks down, but you need another factor Example: Rain

Mass Movements Major Types Creep ( to slip or gradually shift position) and Slump (to fall or sink suddenly.) Creep is the slow movement of sediment down an incline -- so slow that it sometimes takes place over several years. With creep, the adherence of the sediment to the bedrock is hampered, but not completely destroyed. Creep often occurs in areas that have experienced repeated freezing and thawing, which changes the structure and composition of the soil. In slump, a large segment of sediment breaks off in one piece rather than in lots of segments. It occurs when the base can no longer support the weight of what's on top. The sediment involved in slump is usually wet or claylike, and water is often the factor that causes it to fall. Water either adds mass to the top layer of sediment or wears the soil away at the base, weakening the connection between the top and bottom layers.

Causes of Landslides Explanation of Causes Construction Environmental Man-Made Water: Perhaps the most common trigger of a landslide, water reduces the friction between the bedrock and the overlying sediment, and gravity sends the debris sliding downhill. Earthquakes: If the Earth's crust vibrates enough to disrupt the force of friction holding sediments in place on an incline, a landslide can strike. Wildfires: Plants help to stabilize the soil by holding it together like glue with their roots. When this glue is removed, the soil loosens, and gravity acts upon it much more easily. The loss of vegetation after a fire makes the razed land susceptible to slides. Man-made causes: Humans make landslides more likely through activities like deforestation, overgrazing, mining and road-building. Remember when we explained that vegetation acts like glue, holding the soil in place? These activities rob that glue from the land, increasing the probability for a landslide.

How can we avoid Landslides? Building Drainage pipes Reforestation (the action of renewing a forest) Careful Planning: When building near slopes and hazardous areas We cannot completely avoid Landslides but we can discourage them by doing some things. We can have Drainage pipes installed into slopes that can carry away excess water, and impermeable membranes like plastic sheeting can prevent water from building up and dislodging the soil Reforestation is a good deterrent to landslides as well Perhaps the most important thing people can do to avoid the dangers of landslides is to avoid building in hazardous zones. Ideally, buildings shouldn't be placed on steep slopes or in drainage areas.