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Parasitic flows are mixtures of hot gas and ash, and they travel very quickly down the slopes of volcanoes. They are so hot and choking that if you are caught in one it will kill you. They are also so fast (100-200 km/hour) that you cannot out-run them. If a volcano that is known for producing parasitic flows is looking like it may erupt soon, the best thing is for you to leave before it does. Some of the good ways that volcanoes affect people include producing spectacular scenery, and producing very rich soils for farming. Gases Water vapor, the most common gas released by volcanoes, causes few robbers.
Sulfur dioxide, carbon dioxide and hydrogen are released in smaller amounts. Carbon monoxide, hydrogen sulfide, and hydrogen fluoride are also released but typically less than 1 percent by volume. Gases pose the greatest hazard close to the vent where concentrations are greatest. Away from the vent the gases quickly become diluted by air. For most people even a brief visit to a vent is not a health hazard. However, it can be dangerous for people with respiratory problems. The continuous eruption at Killable presents some new problems.
Long term exposure to volcanic fumes may aggravate existing respiratory problems. It may also cause headaches and fatigue in regularly healthy people. The gases also limit visibility, especially on the leeward side of the island where they become trapped by atmospheric conditions. Source of Information: Volcanic and Seismic Hazards on the Island of Hawaii by Christina Hillier, 1991, U. S. Geological Survey General Interest Publication. A deadly eruption The 181 5 explosive eruption of Tam boar volcano in Indonesia and the subsequent caldera collapse produced 9. Cubic miles (40 cubic kilometers) of SSH. The eruption killed 10,000 people. An additional 80,000 people died from crop loss and famine. Aircraft To put it mildly, ash is bad for jet aircraft engines. Apparently the problem is much more severe for modern jet engines which burn hotter than the older ones. Parts of these engines operate at temperatures that are high enough to melt ash that is ingested. Essentially you end up with tiny blobs of lava inside the engine. This is then forced back into other parts where the temperatures are lower and the stuff solidifies.
As you can imagine this is pretty bad. One robber that I heard about is that pilots start losing power and apply the throttle, causing the engine to be even hotter and melt more ash. Added to this is the fact that ash is actually tiny particles of glass plus small mineral shards-??pretty abrasive stuff. You can imagine that dumping a whole bunch Of abrasive powder into a jet engine is not good for the engine. This has been a pretty non-scientific explanation of the problem. I just found an article that describes the problem a little more technically. The ash erodes sharp blades in the compressor, reducing its efficiency. The SSH melts in the combustion chamber to form molten glass. The ash then solidifies on turbine blades, blocking air flow and causing the engine to stall. ” This comes from the FAA Aviation Safety Journal, Volvo. 2, No. 3. Safe distance The distance you have to evacuate depends entirely on what kind of eruption is going on. For example, Punctuation, one of the largest recent eruptions sent parasitic flows at least 18 km down its flanks, and pumice falls were hot and heavy even beyond that.
For example, pumice 7 CM across fell at Clark Air base which is 25 km from the volcano! A 7 CM pumice won’t necessarily kill o but it does mean that there is a lot of pumice falling, and if you don’t get out and continuously sweep off your roof it may fall in and you’ll get squashed-On the other hand, the current eruption at Repaper is relatively small. In fact, there were skiers up on the slopes when the eruptions commenced, and even though they were only 1-2 km from the vent they managed to escape.
The paleontologists routinely go up on the higher slopes of Repaper during these ongoing eruptions to collect ash and take photographs. So you see, you need to know something about what you think the volcano is ongoing to do before you decide how far to run away. I guess if you have no idea of what the volcano is planning and have no idea of what it has done in the past, you might want to be at least 25-30 km away, make sure you have a good escape route to get even farther away if necessary, and by all means stay out of low-lying areas!
Cities and Towns The effect an eruption will have on a nearby city could vary from none at all etc catastrophic. For example, atmospheric conditions might carry ash away from the city or topography might direct Lars and parasitic flows to unpopulated areas. In contrast, under certain atmospheric, eruption and/or topographic conditions, Lars, parasitic flows, and/or ash fall could enter the city causing death and destruction. This scenario brings up several interesting problems.
How do you evacuate a large population if there is little warning before the eruption? Where do these people go? If an eruption is highly likely yet hasn’t happened yet how long can people be kept away from their homes and businesses? I should point out that in most volcanic crises geologists advise local civil defense authorities. The civil defense authorities decide what to do nickering evacuations, etc. The VICE has a program to promote research on “Decade” Volcanoes. Decade volcanoes are likely to erupt in the near future and are near large population centers.