The next move is up to the volcano. Emergency officials are trying to determine if as 25-minute eruption by the Volcano Turrialba late Wednesday night was a hint of what is to come.
So far the biggest result has been the dusting of a good part of the metro are with a thin layer of ash and concern about the welfare of school children near the mountain.
Emergency officials closed Parque Nacional Irazú because of the noxious gases given off by its nearby sister volcano. Five cantons around the mountain, Turrialba, Jiménez, Alvarado, Oreamuno and Cartago Centro, are under an alert. The Comisión Nacional de Prevención de Riesgos y Atención de Emergencias suggested that classes not be held today in these five cantons due to the effects of the gas and any residual ash.
Some residents as far away as Alajuela reported hearing explosions that they thought came from the volcano. But the noise probably was thunder.
The ash fell in a triangular pattern southwest of the volcano. The Observatorio Vulcanologico y Sismologico said that ash fell in San Gerardo de Irazú, San Ramón de Tres Ríos, Coronado, Moravia, Curridabat, Desamparados, Aserrí, Escazú, Santa Ana, Belén, Guácima de Alajuela, Río Segundo de Alajuela, San Pedro Montes de Oca, Guadalupe, San José and parts of Heredia.
The Dirección General de Aviación Civil issued a warning to commercial passenger jets involving an area with a radius of 20 miles of the volcano and to a height of 19,000 feet. The volcano continues to spout a column of gas.
Many who lived near the volcano already have moved elsewhere. A few who remained were evacuated early Thursday. The ash was more dense closer to the volcano and some pastures could not be used.
The eruption was between 11:10 and 11:35 p.m. Wednesday, but scientists had been studying the mountain for several days due to rumblings and low-level seismic shocks.
Most of the reports on the volcano have come from the Observatorio at Universidad Nacional. The volcano experts were at the scene and one participated in a flyover earlier today. The eruption appears to have made internal changes in the volcano crater.
Now the experts are trying to find out if the eruption is a result of gas that has built up or a mass of magma within the mountain. The later could mean a major eruption.
The eruption, the dusting of ash and clips of past eruptions made great television Thursday. The major stations devoted at lest half their air time to the event.