Turrialba, Costa-Rica : recent landslide in the active crater.

Turrialba, Costa-Rica : recent landslide in the active crater.

Report on field observations after the eruption of October 16, 2015.

The deposits indicate a moderate energy eruption similar to those that occurred last year.
On October 18, officials of the OVSICORI visited the Turrialba volcano, to maintain permanent gas monitoring stations and study the deposits of the eruption that took place on October 16, 2015 at 17:49.
The researchers found deposits of thin (<1 mm) of fine ash near the Mirador and in the direction of Silvia. Bombs up to a diameter of 20 cm were found in the southwestern edge of the crater, and a solar panel located in a west side of monitoring station of the active crater was destroyed by ballistic fall / lapilli (~ 2 cm in diameter).

 By the number of observed impacts on the solar panel, it can be calculated that about 20 lapilli (1 cm to several centimeters in diameter) per square meter fell to 250 m to the south-west of the active crater. In the same place we find ~ 0.5 cm of ash. To the northwest edge of the active crater, a layer of fine ash from 8 cm thickness was measured, and this layer is deposited on top of a small pyroclastic flow in the southwest of the central crater. Justifiants elements are the size characteristics, the presence of gas ducts during the sedimentation and temperature (> 70 ° C to 40 cm deep in a place without fumarole). This pyroclastic flow was observed by webcam, on April 23, 2015.
 The preliminary observation of ash in the laboratory of petrology reveals characteristics closely resembling those of previous eruptions with a major presence of weathered material and possibly of about 5-10% by volume of fresh material.

Also, it is observed with evidence on the ground a recent landslide in the active crater. Rock falls are very common with the instability of very vertical walls, but the size of the slide and the absence of ash covering the wall suggests that it occurred in recent days.

 21/10/2015. Turrialba, Costa-Rica :



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