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Poas Volcano Goes Active (updated from Sept 2011 report)

Poas Volcano is a short drive "up the hill" from Pura Vida hotel - we are 31km from the summit at 2708 meters or 8,884 feet. There are only a few places in the world where you can drive up close to the edge of an active volcanic crater, and Poas Volcano National Park is one of them.

There are two craters you can visit (under normal circumstances) - the largest (Poas) is nearly 1.5 km wide - the smaller is a lake with surprisingly clear water called Botos. Poas has been described as sometimes resembling "a scene from Dante's Inferno". When the park is open, sulfuric gasses puff from vents 300 meters below the observation platform. Surrounding the smaller cone is a dense forested area that is one of the few remaining habitats of the scarlet macaw (though we have not seen macaws on our trips up there).

During heightened volcanic activity the park may be closed (though that hasn't happened often). Poas is a stratovolcano with several eroded calderas, cones, and two crater lakes near its summit. Poas has erupted at least 39 times since 1828 and is in state of nearly continuous mild activity. Most of the eruptions are phreatic (which results in hot rocks or lava being thrown up through the lake). Explosions vary in strength. Some explosions eject material about 1,500 feet (500 m) above the lake. The lake (and steam) is very acidic, with a pH of close to zero.

The news items below were culled from local news reports each day including Observatorio Vulcanológico y Sismológico de Costa Rica (OVSICORI-UNA), La Nacion and AM Costa Rica (a local electronic news sheet).


Drive 31 KM up passing a beautiful coffee growing area until you reach higher elevations known for their flower growing and beautiful mountain strawberries.  You will pass into a beautiful area on the slopes of Poas resembling alpine scenery with tropical vegetation.

As you drive past rustic villages and mountain lanes shaded by trees you will move through different climate zones until you reach the summit - sometimes chilly so long pants and a jacket (rain gear in the wet season) are usually recommended.

Gustavo's Coffee Shop, road to Poas - friend to the birds

Poas needs to be visited first thing when the gates open at 8am if possible as clouds invariably will come in later in the day making viewing impossible.

But make sure you stop and "smell the roses" at Gustavo's Colibri Cafe. There's a free tasting of his special coffee blend if you remember to ask. A delightful little place.  On the way down we recommend the Fresas Restaurant in the same area - just delightful.  And the strwaberries are from the slopes of Poas.


Over the last year or so, Poas has been heating up with increased phreatic eruptions (rocks being shot through the lake).   Check out youtube and others for guests videos.

 This article is from AM Costa Rica (a local rag):  "After years of relative calm, the dome of the Volcán Poás crater is registering high temperatures and emitting gas plumes that may go a kilometer in the air.

That's the report from the Observatorio Vulcanológico y Sismológico de Costa Rica. The agency, which is affiliated with Universidad Nacional in Heredia, said that staffers observed that the dome, a lump of volcanic material on the edge of the crater, was incandescent.  This is similar to what has been observed in 1981 (see this photo).

The glow is caused by the high temperatures under the materials.

Lately the temperature has soared to more than 850 C., about 1560 F. Researchers don't really know because the high temperature broke the device they were using to measure the heat.

The vents in the dome are liberating quantities of sulfur dioxide, hydrogen sulfide, hydrogen chloride and also vast amounts of water vapor, they said.

Staffers went into the crater near the dome Aug. 9 and noticed that gas emissions below are agitating the highly acidic lake in the crater. However, in the four hours they were there, there was no eruptions, they reported. The lake continues to be about 51 degrees C., about 124 F. Staffer María Martínez did manage to capture a kilometer-high plume of gas jetting from the dome last May 18.  The researchers also used a thermal imaging camera to photograph the hot spots in the dome. The camera is able to cut through the haze and clouds that usually are found in the crater.

The crater and dome have not yet reached the temperatures registered in 1981 to 1983. The dome is easily viewed from the visitor's observation area."

Thermal imaging on the "dome of Poas" 2011

The PDF report from OVSICORI-UNA can be found here.  The OVSICORI images are from that report, other images from the Pura Vida Hotel, Alajuela.


The following is the Pura Vida Hotel log of events surrounding a series of previous eruptions in 2006

March 24th - Volcan Poas Awoke

On the road up to Poas

After 12 years of relative inaction surprised scientists, local residents and tourists with two eruptions. The first eruption was at 12:05 pm when a column of water and sediment was blown some 40 meters into the air.

The second eruption occurred at 7:53 pm and contained ash and solid material that rose some 200 meters (600 feet) in height, as reported by the Comisión Nacional de Atención de Emergencias (CNE)." The volcano which overlooks the city of Alajuela and can be seen from most of Pura Vida is being evaluated by scientists. Poas summit was closed that day but all other areas are open. This photo was from before this recent activity.

March 25th - Five New Eruptions
Bad weather complicated scientists investigating just what is currently occurring inside the volcano as the colossus launched rocks from the crater. The new eruptions began at 6:50 am, but no material has been ejected outside the current crater.

March 26th - Experts Analyzing Poas Eruptions
Three more eruptions were registered yesterday in Poas volcano, located 35 kilometers to the northwest of San Jose, in the province of Alajuela. P oas entered this current period of activity on Friday after remaining calm for 12 years.

Phreatic eruption from the Volcano Studio, Pura Vida Hotel

According to Lidier Esquivel, jefe de Prevencion de la Comision Nacional de Emergencias (CNE), the eruptions occurred yesterday at 12:00 noon, 4:38 and 5:00 pm. Two of them were of medium intensity, but the second one at 4:38 pm blew a column of gas, water and sediments to a height of at least 150 meters. None of the eruptions has sent material beyond the main crater of the volcano, which is 1,000 meters in diameter and 350 meters in depth. "It worries us that with the eruptions the level of the water in the Crater Lake has diminished and there is an increase in the temperature of that water," said Juan Dobles, head of the Poas Volcano National Park.

(And from: Staff from OVSICORI-UNA visited the east side of the volcano to confirm material charged with water, blocks and sediments from the bottom of the lake. Impact craters were documented in one area ranging from 300 to 700m beyond the source point. Crater size range from some cm to 70cm while, blocks associated ranged from few cm to 50cms and they were scattered randomly in the visited area.

Although they did not reached the extracrater area. Fine and superfine sediments were also documented and collected for later analysis. The area visited showed a gray appearance although the rainy conditions accumulated small ponds of such sediments in crevices and lower drainage.

Recent acid rain effect on umbrella plant at summit

Material collected is composed of preexistent solid material from the bottom of the lake heavily altered by the action of acid and hot conditions during the last 12 years. Some of the more friable samples consist of compacted sediments that have aggregated miscellaneous granulometries.  Up to Monday 27 the tremor disappeared to resume normal seismic activity.

March 27th - May Reopen With Limited Access
Volcán Poás will be under close watch for three more days as scientists try to figure out if activity since Friday is an indication of a much larger eruption yet to come. Officials also said they wanted to plan ways of protecting visitors to the Parque Nacional Volcán Poás when it is finally opened. They are talking about letting spectators enter in small, closely controlled groups and restricting access to some areas.

View from Poas visitors deck on a quiet and beautiful day

The volcano crater gave out two more eruptions Monday, bringing the total near 15 since midday Friday. So far all of the eruptions have been confined inside the volcano crater. The crater gives off hot gases. Nearly 300,000 tourists visit the volcano and its crater overlook each year.

March 28th - May Reopen?
Volcán Poás blew what we believe to be a cloud of steam and ash around 6pm as dusk settled. A couple of photos of that event are at right taken from Pura Vida.

March 31st - Still Closed
Park officials are trying to open the park for small groups of 50 starting April 1st. Park access will be limited but plans are to allow access to the main rim. Botos lake and some of the walkways will remain closed.

April 1st - Restricted Access at the "bubbling cauldron"
We took a ride to the park April 1st. 31km up the hill from the Pura Vida Hotel. Arrived at 8am along with a few early arrivals. Park is open - park guards handed out special instructions for viewing. 1 hour in the park, restricted access, 20 minutes at the rim, evacuation vehicles, ambulance and breathing equipment available.

We parked and walked up after chatting with a government official who was interested in our steam plume photos from a couple of days ago as such events can't be seen from the summit.

A brisk 10 minutes walk gets you to the rim passing the results of recent acid rain from the crater. The results are obvious on the fragile umbrella plants common to high elevations here along the easy path to the viewing area at the rim of the crater.

The sight is nothing short of "awsome" however much that word has been abused of late. A constant shifting of steam from the hot acid lake, constant shifts and changes from the many fumaroles including some with interesting martian green surroundings. The formerly sky blue lake is now a steaming white and everyone is advised to be cautious.

We stayed transfixed by the constantly changing vista and the inspiring forces of nature bubbling in and around the crater lake.


Continued hot spot on left side of crater, fumaroles around lake, lake at normal height perhaps a little low, periodic huge steam clouds through the lake covering the entire crater for some minutes.