LANDSLIDES IN ILIOLITIC AND MARLY FORMATIONS - EXAMPLES FROM NORTH-WESTERN GREECE

Landslides in iliolitic and marry formations are investigated at two r epresentative sites in northern Greece. The first case concerns an ili olitic tectonic formation between Pindos and Ionian flysch while the s econd concerns the marls of the molasses of the Mesohellenic Basin. Bo th areas present a high relief, with steep slopes and significant rain fall. The above formations were studied using both in situ and laborat ory techniques. According to our study, these formations present more or less similar mechanical properties, but different behaviour in rela tion to landslide occurrence; they are very hard in dry conditions but lose their resistance rapidly under wet conditions. In the first case . the rainwater penetrates the iliolite causing landslides of soil typ e. In the second the rainwater does not penetrate the marl creating a surface saturated zone. The material drys rapidly creating cracks and flakes which accumulate at the toe of the slope. This weathering cause s caving at the base of the overlying sandstone which presents topplin g and sliding phenomena.