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THE NATIONAL GEOGRAPHIC MAGAZINE 



Photo by J. Fid Tristan 



Poas crater is more than half a mile wide. Its walls are steep and precipitous and about 

 800 feet deep. The geyser ejects mainly water, but sometimes ashes and mud. In this picture 

 rising mud can be seen distinctly in the center. 



of late an unusual activity coincident 

 with the long series of cjuakes that have 

 just afflicted Costa Rica. 



Poas has at least two craters. The 

 higher one on the pyramidal top of the 

 mountain is extinct and filled by a mar- 

 velous sheet of blue, cold water, framed 

 in an exuberant border of semi-tropical 

 vegetation; the other crater, i.ooo feet 

 lower, showing at its bottom a lead- 

 colored lagoon, is surrounded by almost 

 vertical jagged walls of gray pumice and 

 other eruptive materials. This is a gey- 

 serian basin, the eruptions of which 

 occur at irregular intervals of from 12 

 to 20 minutes or more, and with variable 

 intensity. At times the water, which 

 tastes like strong vinegar, is hardly dis- 



turbed ; at other times a heavy column 

 accompanied by dense clouds of vapor 

 surges to a variable height, creating a 

 furious tempest on the usually placid 

 lake. 



In 1889 the writer witnessed the rise 

 of a column of muddy water about 1,000 

 feet in height, while in January last it 

 attained, according to official reports, no 

 less than 13,000 feet. Like Irazu, Mount 

 Poas is of very easy access, and of late 

 it has become very popular on account 

 of the variety of its natural beauties. 

 Before the January eruption of the pres- 

 ent year it was not known to have had 

 any dangerous outburst in historical 

 times. 



The volcanic cordillera of Costa Rica 



