Posted on 08/29/2003 5:37:16 PM PDT by blam
Signs of an eruption
For days before the eruption the volcano had been screaming 'I'm about to explode'
Bernard Chouet
A scientist has found a way to use earthquakes to predict when volcanoes will erupt. Swiss scientist Bernard Chouet fell in love with volcanoes when he witnessed spectacular fountains of lava spewing from Sicily's Mount Etna in 1969.
Now at the US Geological Survey, Chouet has devoted his career to finding a way to predict deadly volcanic eruptions. He is haunted by a disaster in South America that killed 25,000 people.
When Colombia's Nevado del Ruiz volcano erupted in 1985, it melted a glacier capping the mountain. Water and volcanic ash combined to produce devastating mudflows that wiped the entire town of Armero off the map.
By then Chouet had developed a theory that volcanic eruptions should be preceded by a type of earthquake he called a long period event.
Chouet believed that long period events were a sign that pressure was building up inside a volcano.
When he finally saw the earthquake records from Nevado del Ruiz, a year on from the disaster, he was horrified.
Tragic misjudgement
Chouet saw long-period events all over charts. For days before the eruption the volcano had been screaming "I'm about to explode" but no one had heard the warning.
Vesuvius volcano
In the early 1990s another Colombian volcano, Galeras, became restless. Long period events had again appeared on the charts - a clear sign of an impending eruption, according to Chouet.
But US volcanologist Stanley Williams was sceptical about Chouet's approach. Apart from the long period events the volcano was completely quiet.
So on 14th January 1993 Williams led a group of scientists into the crater of Galeras to measure gas emissions.
It was a tragic misjudgement. As they were preparing to leave the crater the volcano erupted, killing six of his colleagues and three tourists. Williams himself was severely injured.
In December 2000 Chouet was vindicated in dramatic fashion. For several years the mighty Popocatépetl on the outskirts of Mexico City had been gently steaming.
Fumarole volcano But then the long period events started - so many that they merged into a continuous tremor that could be felt in nearby villages.
Using Chouet's methods scientists at the National Centre for Prevention of Disasters in Mexico City predicted that there would be a large eruption in two days. The government evacuated tens of thousands of people.
Forty eight hours later, bang on time, the volcano erupted spectacularly. It was Popocatépetl's largest eruption for a thousand years and yet no one was hurt.
Here are some highlights from their summary of effects:
1. The explosions were heard on Rodriguez Island, 4653 km distant across the Indian Ocean, and over 1/13th of the earth's surface.
2. Ash fell on Singapore 840 km to the N, Cocos (Keeling) Island 1155 km to the SW, and ships as far as 6076 km WNW. Darkness covered the Sunda Straits from 11 a.m. onthe 27th until dawn the next day.
3. Giant waves reached heights of 40 m above sea level, devastating everything in their path and hurling ashore coral blocks weighing as much as 600 tons.
4. At least 36,417 people were killed, most by the giant sea waves, and 165 coastal villages were destroyed.
5. When the eruption ended only 1/3 of Krakatau, formerly 5x9 km, remained above sea level, and new islands of steaming pumice and ash lay to the north where the sea had been 36 m deep.
6. Every recording barograph in the world ducumented the passage of the airwave, some as many as 7 times as the wave bounced back and forth between the eruption site and its antipodes for 5 days after the explosion.
7. Tide gauges also recorded the sea wave's passage far from Krakatau. The wave "reached Aden in 12 hours, a distance of 3800 nautical miles, usually traversed by a good steamer in 12 days".
8. Blue and green suns were observed as fine ash and aerosol, erupted perhaps 50 km into the stratosphere, circled the equator in 13 days.
9. Theree months after the eruption these products had spread to higher latitudes causing such vivid red sunset afterglows that fire engines were called out in New York, Poughkeepsie, and New Haven to quench the apparent conflagration. Unusual sunsets continued for 3 years.
10. Rafts of floating pumice-locally thick enouth to support men, trees, and no doubt other biological passengers-crossed the indian Ocean in 10 months. Others reached Melanesia, and were still afloat two years after the eruption.
11. The volcanic dust veil that created such spectacular atmospheric effects also acted as a solar radiation filter, lowering global temperatures as much as 1.2 degree C in the year after the eruption. Temperatures did not return to normal until 1888.
The book is full of many more amazing bits of information. Hopefully these small excerpts will be useful to you.
Sincerely,
Scott Rowland (not jpsb ;)
Amazing what a couple seasons of crop failures will do to a society.
These days we say no country is more than three meals from a revolution.
Funny thing about revolutions - the rabble tend to kill off the rulers and in-tuh-lex-shuls...
Read the articles linked in post #53 & 56. Eyewitnesses said it was dark.
Arthur, America And The Comet (Speculative)
LOL. I have some N95 masks that I'm planning to sell for $10.00 this winter when SARS resurfaces.
Very good, sensible advice. I advise running down to Home Depot and picking up a proper hose nozzle while you still can. /sarcasm.
Actually, having survived St. Helens micro-eruption (compared to Yellowstone possibilities) and having been inconvenienced for a few weeks by it, I am in awe of volcanos and the possibility of substantial destruction. Here, in eastern Washington, I can just imagine no wheat or potato production for 2-3 years, and having all the irrigation reservoirs and canals jammed with ash. No irrigation => no production in this part of the country. If the ash is anything like St. Helens, it essentially turns to concrete after a few wet/dry cycles.
Also, any major geo/weather event like that would tend to bring out fungal diseases and other agricultural pathogens which are normally kept in check.
I don't understand the question?
The Russian army fought the last half of WW2 on Spam. I have a little tuna set aside too, lol.
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