Important historical landslides in Barva volcano (Costa Rica) and its transformation in debris flows

Abstract

A historical analysis was carried out on the main large landslides that have occurred in the foothills of the Barva volcano, which have been transformed into volcanic debris (non-eruptive lahars). The first record is associated with the earthquake that occurred on February 15, 1772 that produced large mass movements from the upper parts of Barva, in the headwaters of the Itiquís river, which arrived near Alajuela as a cosismic debris flow. Towards the NE of the Danta cone, two landslides occurred in the same sector, one between the years 1963 and 1964 in the headwaters of the General river that created a lake by damming the river; it had a minimum volume of 0.02 km3. The other occurred in 2006, where a mass of approximately 0.05 km3 slid and reached an estimated speed of about 37 m/s (133 km/h), until it was transformed into a debris flow that traveled more than 20 km downstream. These landslides in the headwaters of the General river occurred in an area of very strong slopes with profuse hydrothermal alteration and the presence fumaroles and hot springs, on which lie lava flow fields and recent pyroclastic rocks. This and other sectors indicated at work are prone to similar landslides in the future and their transformation into debris flows, which pose a danger because they can travel to populated areas many kilometers downstream.