Eruptions can be much more powerful than most people expect

History shows that volcanoes should not be underestimated.

Mount Vesuvius killed an estimated 16,000 persons when it exploded in 79 A.D. The mountain sent up plumes of ash and smoke 33 kilometers into the air, some 20.5 miles.

The pyroclastic flows entombed the Roman communities of  Pompeii and Herculaneum, which now are museums. Ash fell as far away as what is today Istanbul.

Mount St. Helens exploded in the U.S. State of Washington in 1980. The column rose up an estimated 80,000 feet and rained ash on 11 U.S. states. Some 15 persons died and the economic loss approached $3 billion.

The Irazú volcano staged a series of eruptions in 1963, and although there was no serious damage, ash rained on San José and other areas of the Central Valley for two years.

Mount Arenal in Costa Rica erupted in 1968 and wiped out  Tabacón, Pueblo Nuevo and San Luís. The explosion sent rocks the size of Volkswagens miles in all directions and destroyed much of the area livestock, agricultural land and several communities. Refugees flocked to Ciudad Quesada. The death toll was 87.

Mount St. Helens and Mount Vesuvius gave ample signs of activity with local earth tremors. The Arenal explosion was a surprise.

By these eruption standards, the current activity at the Turrialba volcano is minor. The 3,340-meter, 10,958-foot mountain had multiple eruptions Monday, at 10:30 a.m., 1:35 p.m., 2:30 p.m., 2:45 p.m., 3:09 p.m., 3:30 p.m. and 4:01 p.m., according to the Observatorio Vulcanológico y Sismológico de Costa Rica at Universidad Nacional. The ash column rose up to 500 meters to 1,000, nearly 1,700 to 3,400 feet.

Ash was reported falling in San Isidro del Guarco, Turrialba, Paraiso, Cartago, Alajuela, Curridabat and Tibás. The ash dispersal depends on the wind direction.

So far officials have taken steps to close the mountain and the Parque Nacional Volcán Turrialba that surrounds it. Farmers continue to work their land on the flanks of the

Pompeii residents may have thought that the distance from  Vesuvius was enough to protect them. This is what is left of the city’s forum.

Pompeii residents may have thought that the distance from Vesuvius was enough to protect them. This is what is left of the city’s forum.

mountain despite the ash fall while others tend and milk their cows.

Most scientific observers expect the mountain to go back to sleep. The alternative would be an unpleasant surprise because pyroclastic flows can move at great speeds for miles.

Many who died in Pompeii were at the sea coast awaiting evacuation. Many died in their sleep because they did not take the activity in the mountain seriously and waited too long to leave.

The national emergency commission tries not to be alarmist when it suggests basic preparations, like three days of food, plenty of water on hand, flashlights, extra batteries and a battery-powered radio. These precautions could apply to persons well away from any volcano. After all, the Central Valley has active volcanoes to the west and to the east, including Poas, Barva, Irazú and Turrialba.

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