Unlike mountains, which are pushed up from the earth’s crust, volcanoes are formed by their buildup of lava, ash flows, and airborne ash and dust.
When pressure from gases and molten rock becomes strong enough to cause an explosion, it erupts and starts to spew gases and rocks through the opening.
Volcanic eruptions can hurl hot rocks (sometimes called tephra) for at least 20 miles (32 km) and cause sideways blasts, lava flows, hot ash flows, avalanches, landslides and mudflows (also called lahars).
Fresh volcanic ash is not like soft ash in a fireplace. Volcanic ash is made of crushed or powdery rocks, crystals from different types of minerals, and glass fragments that are extremely small like dust. But it is hard, gritty, smelly, sometimes corrosive or acidic (means it can wear away or burn things) and does not dissolve in water.
The ash is hot near the volcano but is cool when it falls over great distances. Ashfall is very irritating to skin and eyes and the combination of ash and burning gas can cause lung irritation or damage to small infants, the elderly or people with breathing problems.
Did you know…
BEFORE A VOLCANIC ERUPTION:
Prepare – Try to cover and protect machinery, electronic devices, downspouts, etc. from ashfall. Learn more by visiting the USGS Volcano Hazards Program site at https://volcanoes.usgs.gov/volcanic_ash/
Learn alert levels – Ask emergency management office which volcano warnings or alert levels are used since they vary depending on where you live (can be alert levels, status levels, condition levels or color codes).
Make a plan – Develop a Family Emergency Plan and Disaster Supplies Kit. (Note: Put in goggles or safety glasses and dust masks for each family member to protect eyes and lungs from ash.) Download a free 56-pg PDF portion of Fedhealth's 266-page book that includes tips on making a plan and kit and more.
Okay to go? – Don’t go to active volcano sites unless officials say it’s okay.
Be ready to evacuate – Listen to local authorities and leave if you are told to evacuate.
DURING A VOLCANIC ERUPTION:
Listen – Do what local authorities say, especially if they tell you to leave!
Leave – If you are told to evacuate, DO IT! Don’t think you are safe to stay home … the blast can go for miles/kilometres and cause wildfires and other hazards!
Watch out – Eruptions cause many other disasters:
IF INDOORS – Stay in, but be aware of ash, rocks, mudflows or lava!
IF IN A VEHICLE – Avoid driving unless absolutely required.
AFTER A VOLCANIC ERUPTION:
Listen – Local authorities will say if and when it’s safe to return to area (especially if you had to evacuate) and give other updates when available.
Water – Check with authorities before using water, even if eruption was just ash fall (gases and ash can contaminate water reserves). Don’t wash ash into drainpipes, sewers or storm drains since wet ash can wear away metal.
What to wear – If you must be around ash fall, you should wear long sleeve shirts, pants, sturdy boots or shoes, gloves, goggles (or safety glasses) and keep your mouth and nose covered with a dust-mask or damp cloth.
Ash – Dampen ash before sweeping or shoveling buildup so it’s easier to remove and won’t fly back up in the air as much – but be careful since wet ash is slippery. Wear protective clothing and a dust mask too. Realize ash can disrupt lives of people and critters for months.
Protect – Cover machinery and electronic devices like computers.
Above extracted from IT’S A DISASTER! …and what are YOU gonna do about it? by Bill and Janet Liebsch ~ download a free 56-pg portion in PDF
USGS Volcano Hazards Program http://volcanoes.usgs.gov/
Smithsonian Institute’s Global Volcanism Program www.volcano.si.edu
Nice article, a lot of info I did not know
Thanks Bob. I thought I had posted this a while back but snooped thru all group posts and nope. And, since Kilauea is spewing and wrecking havoc over in Hawaii, I thought it might be helpful.
CBS News video from 4-May-2018 shows some footage of Hawaii's Kilauea volcano that has forced about 1,700 people to leave their homes on the Big Island, and the state National Guard has been mobilized.