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| # Volcanoes                                                           |
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| A [volcano]{.underline} is a vent through which molten rock escapes   |
| to the Earth's surface. Unlike other mountains, which are pushed up   |
| from below, volcanoes are built by surface accumulation of their      |
| eruptive products---layers of lava, ashflows, and ash. When pressure  |
| from gases within the molten rock becomes too great, an               |
| [eruption]{.underline} occurs.                                        |
|                                                                       |
| The United States is third in the world, after Japan and Indonesia,   |
| for the number of active volcanoes. Since 1980, as many as five       |
| volcanoes have erupted each year in the United States.                |
|                                                                       |
| Eruptions are most likely to occur in Hawaii and Alaska. For the      |
| Cascade Range in Washington, Oregon, and California, volcanoes erupt  |
| on the average of one to two each century.                            |
|                                                                       |
| Also, when Cascade volcanoes do erupt, high-speed avalanches of       |
| [pyroclastic flows, lava flows (hot ash and rock), and                |
| landslides]{.underline} can devastate areas 10 or more miles away.    |
| Lahars can inundate valleys more than 50 miles downstream.            |
|                                                                       |
| The island of Hawaii (the largest of the Hawaiian islands)            |
| experiences thousands of earthquakes associated with active volcanoes |
| each year. While most of these are too small to feel, about once a    |
| decade a large quake shakes the entire island and causes widespread   |
| damage.                                                               |
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| Volcanoes produce a wide variety of hazards that can kill people and  |
| destroy property. Large explosive eruptions can endanger people and   |
| property hundreds of miles away and can even affect the global        |
| climate.                                                              |
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| Volcanic hazards include:                                             |
|                                                                       |
| -   Toxic gases.                                                      |
|                                                                       |
| -   Lava and pyroclastic flows.                                       |
|                                                                       |
| -   Landslides.                                                       |
|                                                                       |
| -   Earthquakes.                                                      |
|                                                                       |
| -   Explosive eruptions.                                              |
|                                                                       |
| Eruptions can be relatively quiet, producing lava flows that creep    |
| across the land at 2 to 10 miles per hour (mph). Explosive eruptions  |
| can shoot columns of gases and rock fragments tens of miles into the  |
| atmosphere, spreading ash hundreds of miles downwind.                 |
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| # Volcanoes (Continued)                                               |
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| [Lava flows]{.underline} are streams of molten rock that either pour  |
| from a vent quietly or erupt explosively as lava fountains. Because   |
| of their intense heat, lava flows are also great fire hazards. Lava   |
| flows destroy everything in their path, but most move slowly enough   |
| that people can move out of the way. The speed at which lava moves    |
| across the ground depends on several factors, including the:          |
|                                                                       |
| -   Type of lava that has erupted.                                    |
|                                                                       |
| -   Steepness of the ground.                                          |
|                                                                       |
| -   Rate of lava production at the vent.                              |
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| Volcanic eruptions can be accompanied by other natural hazards,       |
| including:                                                            |
|                                                                       |
| -   Mudflows (including lahars).                                      |
|                                                                       |
| -   Flash floods.                                                     |
|                                                                       |
| -   Wildland fires.                                                   |
|                                                                       |
| -   Tsunamis (under special conditions).                              |
|                                                                       |
| -   Earthquakes.                                                      |
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| Historically, [lahars]{.underline} have been one of the deadliest     |
| volcano hazards. Lahars are mudflows or debris flows composed mostly  |
| of volcanic materials on the flanks of a volcano. These flows of mud, |
| rock, and water can rush down valley and stream channels at speeds of |
| 20 to 40 miles per hour and can travel more than 50 miles.            |
|                                                                       |
| Lahars can occur both during an eruption and when a volcano is quiet. |
| The water that creates lahars can come from melting snow and ice,     |
| intense rainfall, or the breakout of a summit crater lake.            |
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| # Volcanoes (Continued)                                               |
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| [Volcanic ash]{.underline} is actually fine, glassy rock fragments    |
| that can affect people and equipment hundreds of miles away from the  |
| cone of the volcano. Volcanic ash will:                               |
|                                                                       |
| -   Cause severe respiratory problems.                                |
|                                                                       |
| -   Diminish visibility.                                              |
|                                                                       |
| -   Contaminate water supplies.                                       |
|                                                                       |
| -   Cause electrical storms.                                          |
|                                                                       |
| -   Disrupt the operation of all machinery.                           |
|                                                                       |
| -   Collapse roofs.                                                   |
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| [The key steps in volcanic eruption preparedness are:]{.underline}    |
|                                                                       |
| -   [Understanding the risk]{.underline}. Take time to learn about    |
|     the risk from volcanic eruption in your area.                     |
|                                                                       |
| -   [Talking to your insurance agent]{.underline}. Find out what your |
|     homeowner's policy will or will not cover in the event of a       |
|     volcanic eruption.                                                |
|                                                                       |
| -   [Prepare a disaster supply kit]{.underline}, including goggles    |
|     and dust mask for every family member.                            |
|                                                                       |
| -   [Developing an evacuation plan]{.underline}. Everyone in your     |
|     family should know where to go if they have to leave.             |
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| -   [Following evacuation orders]{.underline}. Staying at home to     |
|     wait out an eruption, if you are in a hazardous zone, could be    |
|     very dangerous. Take the advice of local authorities.             |
|                                                                       |
| -   [Avoiding areas downwind and river valleys downstream of the      |
|     volcano]{.underline}. Debris and ash will be carried by wind and  |
|     gravity. Stay in areas where you will not be exposed further to   |
|     volcanic eruption hazards.                                        |
|                                                                       |
| -   [If outside, protecting yourself from ashfall]{.underline}.       |
|     Volcanic ash will cause severe injury to breathing passages,      |
|     eyes, and open wounds, and irritation to skin.                    |
|                                                                       |
| -   [Being prepared for accompanying hazards]{.underline}. Know how   |
|     to respond to reduce your risk.                                   |
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| # Volcanoes (Continued)                                               |
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| Take the following measures to protect yourself from ashfall:         |
|                                                                       |
| -   [Wear long-sleeved shirts and long pants]{.underline}.            |
|                                                                       |
| -   [Use goggles]{.underline} to protect your eyes.                   |
|                                                                       |
| -   [Wear eyeglasses]{.underline} instead of contact lenses.          |
|                                                                       |
| -   [Use a dust mask]{.underline} or hold a damp cloth over your face |
|     to help you breathe.                                              |
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| -   [Stay away from volcanic ashfall areas]{.underline}. The fine,    |
|     glassy particles of volcanic ash will increase the health risk to |
|     children and people with existing respiratory conditions such as  |
|     asthma, chronic bronchitis, or emphysema.                         |
|                                                                       |
| -   [Clear roofs of ashfall]{.underline}. Ashfall is very heavy and   |
|     can cause roofs to collapse, especially if made wet by rainfall.  |
|     Exercise great caution when working on a roof.                    |
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| -   [Avoid driving in heavy ashfall]{.underline}. Driving will stir   |
|     up volcanic ash that can clog engines and stall vehicles. Moving  |
|     parts, including bearings, brakes, and transmissions, can be      |
|     damaged from abrasion.                                            |
|                                                                       |
| ```{=html}                                                            |
| <!-- -->                                                              |
| ```                                                                   |
| -   [If you have a respiratory ailment, avoid contact with any amount |
|     of ash]{.underline}. Stay indoors until local health officials    |
|     advise that it is safe to go outside.                             |
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