Abstract
Particular conditions of topography, climate and geology in Costa Rica, make chis country prone to slope instability. At present, this situation has been accelerated by direct or indirect influence of human activity. Inatability is shown by a wide variety of forms, intensities and extention. Affected zones are not ussually limited to where slope instability occurs but to wider arcas such as river margine, net lawlands and in general, those arcas where the deposits arrive with important amounts of energy. Primary factors of development of instable slopes in this country are: topography (slope angles, irregularíties), climate (rain, humidity), hydrological factors (infiltration, seepage flows, fluvial erosion), geology (soils, lithology structures, geomorphology), surface alteration (weatheríng, hydrothermalism) and others. As a result, various types and forms of land instability haya been recognized: laminar or concentrated erosion, (crevasses, badlands, torrents), solifluction (creep), rock block falls, crown landslides with channelized debris avalanchas, shallow landslides in residual soils (regolithic), ahallowand deep circular landslides, etc. Trigger mechanisms are quite numerous and rarely acting alone, so the comple xity of instabilized areas become higher and the possibility of their control smaller. Seismicity, voloanism, heavy rainfall periods and human activities (road constructions, deforestation, irrational agrarian exploitation systems, quarries and open pit mines), should be accounted also as main causes of generation of this kind of phenomenum, which has multiplied significantly in the last few decades. This situation has affected or menaced very important civil structures, populations, vital linea and agrarían production centers throughout the country.