& USGS

VolcanoA volcano is an opening in the Earth’s crust that allows molten rock, gases, and debris to escape to the surface. Alaska, Hawaii, California, and Oregon have the most active volcanoes, but other states and territories have active volcanoes, too. A volcanic eruption may involve lava and other debris that can flow up to 100 mph, destroying everything in their path. Volcanic ash can travel 100s of miles and cause severe health problems. A volcanic eruption can:

  • Contaminate water supplies.
  • Damage machinery.
  • Reduce visibility through smog and harmful gases that may threaten low-lying areas.
  • Make it hard to breathe and irritate the skin, eyes, nose, and throat.


  • Listen for emergency information and alerts.
  • Follow evacuation or shelter orders. If advised to evacuate, then do so early.
  • Avoid areas downstream of the eruption.
  • Protect yourself from falling ash.
  • Do not drive in heavy ash fall.


  • Ash and gases – Volcanic ash consists of rock, mineral, and volcanic glass fragments smaller than a tenth of an inch in diameter—or slightly larger than a pinhead. Volcanic ash is quite different from the soft, fluffy ash that results from burning wood, leaves, or paper. It is hard, does not dissolve in water, and can be extremely small—ash particles less than 1/1,000th of an inch in diameter are common. It is also extremely abrasive (similar to finely crushed window glass), mildly corrosive, and electrically conductive, especially when wet. Freshly fallen ash grains commonly have surface coatings of soluble components (salts) and/or moisture. These components can make ash mildly corrosive and potentially conductive. The soluble coatings are derived from the interactions in an eruption column between ash particles and volcanic-gas aerosols, which may be composed of sulphuric and hydrochloric acid droplets with absorbed halide salts. The amount of available aerosols varies greatly between eruptions of similar size and volume.
  • Lava Flow – Lava is the word for magma when it erupts onto the Earth’s surface. Lava flows are masses of magma that pour onto the Earth’s surface during an effusive eruption; they include both moving lava and the resulting solidified deposits. Lava flows come in a great variety of shapes and sizes. This is due to the wide range in lava discharge during eruptions, characteristics of the erupting vent and topography over which lava travels, and viscosity of the different lava types.
  • Tephra – Tephra is a general term for fragments of volcanic rock and lava that are blasted into the air by explosions or carried upward by hot gases in eruption columns or lava fountains. Tephra includes large, dense blocks and bombs, and small, light rock debris such as scoria, pumice, reticulite, and ash.
  • Lahar – Lahar is an Indonesian word for a rapidly flowing mixture of rock debris and water that originates on the slopes of a volcano. Lahars are also referred to as volcanic mudflows or debris flows. They form in a variety of ways, chiefly from the rapid melting of snow and ice by pyroclastic flows, intense rainfall on loose volcanic rock deposits, the breakout of a lake dammed by volcanic deposits, and as a consequence of debris avalanches.


  • Know your area’s risk from volcanic eruption.
  • Ask local emergency management for evacuation and shelter plans, and for potential means of protection from ash.
  • Learn about community warning systems. The Volcano Notification Service (VNS) is a free service that sends notifications about volcanic activity. Sign up for alerts at
  • Get necessary supplies in advance in case you have to evacuate immediately, or if services are cut off. Keep in mind each person’s specific needs, including medication. Do not forget the needs of pets.
  • Consult your doctor if you have existing respiratory difficulties.
  • Practice a communication and evacuation plan with everyone in your family.
  • Have a shelter-in-place plan if your biggest risk is from ash.
  • Keep important documents in a safe place. Create password-protected digital copies.
  • Find out what your homeowner’s insurance policy will cover when a volcano erupts.


  • Listen to alerts. The Volcano Notification Service provides up-to-date information about eruptions.
  • Follow evacuation orders from local authorities. Evacuate early.
  • Avoid areas downwind, and river valleys downstream, of the volcano. Rubble and ash will be carried by wind and gravity.
  • Take temporary shelter from volcanic ash where you are if you have enough supplies. Cover ventilation openings and seal doors and windows.
  • If outside, protect yourself from falling ash that can irritate skin and injure breathing passages, eyes, and open wounds. Use a well-fitting, certified facemask such as an N95. The Centers for Disease Control and Prevention (CDC) has a list of certified masks and the maker’s instructions on how to use the masks.
  • Avoid driving in heavy ash fall. If you must drive, then turn off your vehicle’s headlights.
  • If the authorities tell you not to go to where the lava is flowing, don’t go. Hawaii authorities are issuing citations with a fine.


An ash fall can turn daylight into complete darkness. Accompanied by rain and lightning, the gritty ash can lead to power outages, prevent communications, and disorient people. The sky will turn increasingly hazy and “dusty” and sometimes a pale yellow color. Closer to the eruption site, the sky may acquire intense blackness. A strong smell of sulfur may accompany the ash 

fall. Except for the thunder, an odd quietness develops.

Everyone in the area will be exposed to the effects of volcanic ash. Fine grained ash can infiltrate all but the most tightly sealed buildings and machinery. It can also be inhaled deeply into the lungs of people and animals, resulting in difficulty breathing and subsequent loss of energy.  You may find the use of a respirator helpful. It should be air-tight and contain a filter to catch ash and filter out toxic gases. Use a water-soaked bandana over your nose and mouth if caught outside in an emergency. Avoid as much skin contact with ash as possible by covering your body. Ash fall may prevent travel for days because of poor visibility, slippery roads and damage to vehicles. Due to its abrasive character and widespread distribution by winds, ash clouds can be devastating to aviation. If you are traveling by car during an ash fall, you should change the oil and filters in your vehicle frequently, as well as lubricate your vehicle chassis.


The main thing to expect after an ash fall will be the time-consuming, costly and dirty effort by everyone in the affected area to remove and dispose of the ash. Communities need to co-ordinate clean-up efforts so that the ash only needs to be moved once and does not contaminate a previously cleaned site.


Lava flows are streams of molten rock that pour or ooze from an erupting volcanic vent. It is erupted during either explosive or nonexplosive as lava fountains. Its speed may vary and typically moves slowly enough to outrun them, but they will destroy everything n their path. Depending on the viscosity, based on the type of molten rock, the flow can extend ten os kilometers. Depending on the activity this flow may continue for several months or years.

Everything in the path of an advancing lava flow will be knocked over, surrounded, buried, or ignited by the extremely high temperatures. When it cools, lave becomes hardened rock. People are rarely able to use land buried by lava flows or sell it for more than a small fraction of its previous worth.


A moving lahar is like a wet slurry of concrete. As it rushed downstream, the size, speed, and amount of material carried can constantly change. As they slow down, they will deposit some of the load leaving behind devastation. Over a period of weeks to years after a volcanic eruption, the erosion and transportation of loose volcanic deposits can lead to sever flooding in areas far downstream from a volcano.


Listen to authorities to find out when it is safe to return after an eruption.

  • Send text messages or use social media to reach out to family and friends. Phone systems are often busy after a disaster. Only make emergency calls.
  • Avoid driving in heavy ash. Driving will stir up volcanic ash that can clog engines and stall vehicles.
  • If you have any breathing problems, avoid contact with ash. Stay indoors until authorities say it is safe to go outside.
  • Do not get on your roof to remove ash unless you have guidance or training. If you have to remove ash, then be very careful as ash makes surfaces slippery. Be careful not to contribute additional weight to an overloaded roof.


Volcanoes erupt in different ways, pose multiple types of hazards, and their initiation and duration are uncertain. Therefore, authorities and populations at risk must be knowledgeable about the hazards so they can be prepared and flexible in their response. Be aware of current and potentially dangerous conditions. Pay attention to local announcements and become familiar with evacuation routes in your area. If you are instructed to evacuate, do so. Your 72 hour kits should help you get out quickly.







Billie Nicholson, Editor
July 2018

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