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Arenal - Pyroclastic Avalanche Sep. 2003


Arenal eruption page updated: October 30, 2005 in Costa Rica: activity moderate. Hot rocks and lava rolling down every 5 minutes could be seen on the West face. Most recent Arenal Volcano Photos!

Arenal Eruption September 2003

Arenal Volcano Costa Rica, September 5th. 2003 - at 11:55 am today the most spectacular event since the August 23, 2000 eruption occurred when part of the wall of one of the active craters of Arenal collapsed and 4 consecutive pyroclastic avalanches occurred in a lapse of 45 minutes, flowing on the north-west face. See Arenal photos


Arenal Eruption September 2003


Arenal Eruption September 2003

Photo: Carlos León LA NACIÓN


The hot material caused a small forest fire on the slope but the humid and lush tropical vegetation extinguished it.

The spectacular incandescent mixture of hot ashes, rocks & lava (nuée ardente) traveled at an estimate initial speed of 200 kilometers per hour (125 mph) for a distance of 850 meters (2,750 feet) and never endangered the hotels and hot springs which are safely located several kilometers away. As a comparison, the Arenal August 2000 eruption was 2.5 kilometer long (1.5 mile).

There were no victims or property damage.

Nevertheless, the Comisión Nacional de Prevención de Riesgos y Atención de Emergencias (CNE) quickly declared a Green Alert and evacuated and closed for 3 hours the Arenal National Park, Tabacon Hot Springs and one of the hotels with the best views of the lava flow located on the north side of the volcano (see Arenal map): Hotel Los Lagos.

All is now back to normal and everything is re-opened including the Arenal National Park.


Arenal Eruption September 2003

A newswire by Associated Press inaccurately said that that the event was "panicking nearby residents" which we found funny and ridiculous, the hotels and houses being miles away from the crater. The CNE and local authorities are very strict in regards of where activities and construction can take place and permits takes months to obtain. Beside this major attraction is way too important for Costa Rica's tourism industry to risk unnecessarily the lives of residents and visitors.

Observation post were setup by the experts at the Hotel Los Lagos, Mirador Kioro, the National Park and the Guardia Rural (local police) station in La Fortuna.


The tourists visiting the volcano will have stories for their postcards and lots of photos because the weather was perfect for volcano viewing today as it is often the case early morning in rainy season in this region. The ashes and smoke column could be seen from the Mirador Lodge in the mountains of the Monteverde Cloud Forest located 16 kilometers away as the crow flies. The sky was also clear at night and thousands of residents and visitors had the chance of seeing the glowing lava flow.

The Arenal Volcano is active almost every day since 1968 but events like this one are rare. Because the nearby dam on the Arenal Lake is a major source of electricity generation for Costa Rica and the fact that a volcano active for such a long period is a bargain for scientist, as well as one of the major tourist attraction of this country, the volcano is very closely monitored by a sophisticatedSeismological Network. In fact Mr. Fausto Alfaro, the regional director of the Ministerio del Ambiente y Energía (Minae, Environment & Energy Ministry), said that the volcano was under closer observation since a few days before the eruption because instruments were signaling abnormal seismic activity and an avalanche was suspected.

The avalanches are not considered eruptions by scientists and the volcanic activity remains moderate with an average of 540 eruptions of the Arenal Volcano in January 2005 with an average of 22 a day as recorded by the OVSICORI. Click here to read more about how the Arenal works and view the 1968 eruption animation

Because pyroclastic flows travel so fast, we ask visitors to please respect the signs indicating the limits you should not cross when hiking on the trails even if the volcano seems quiet that day. Enjoy the show but from a safe distance!

Source: La Nacion , Costa Rica's national daily in Spanish, Observatorio Vulcanológico y Sismológico (OVSICORI-UNA) and the friends and personnel of the Hotels Montana de Fuego, Arenal Paraiso, Hotel Los Lagos and Tacotal.