Smithsonian Institution
Bulletin of the Global Volcanism Network, v. 20, no. 11/12, November-December 1995
Poas (Costa Rica)  Fumarolic and seismic activity

Poas
Costa Rica
10.20 N, 84.22 W; summit elev. 2,708 m

The surface of the sky-blue crater lake rose in November (20 cm
higher than October); the lake's temperature was 26 degrees C. A
vigorous subaqueous fumarole appeared adjacent the lake's S shore.
The W-terrace fumarole emitted yellow, sulfur-rich gases and
particles; other fumaroles located on the NW-SW terrace emitted
only low amounts of gases. Measured fumarole temperatures were in
the range 94-96 degrees C along the S and SE crater, an area that
produced 100-m-tall gas columns. Gases escaping the pyroclastic
cone had temperatures of 93 degrees C.

During 1-22 November the local seismic station recorded 5,146
events (predominantly of low-frequency), significantly fewer than
the number seen in the two previous months (figure 19).

Information Contacts: OVSICORI-UNA (see Rincon de la Vieja).

Figure 19. Poas seismicity for January-November 1995 recorded at
station POA2 (2.7 km SW of the active crater). Courtesy of
OVSICORI-UNA.