The eruption of Lonquimay volcano and its effects in agriculture

Eduardo Besoaín M.1, Gloria Sepúlveda W.1 y Angélica Sadzawka R.1

The Lonquimay volcano, of late Pleistocene to Holocene age, and dominantly of andesitic composition, is placed in the southern Andean Range of Chile (38º 22' 30"S and 71º 35' 30" W). During its late eruption (25.12.88 - 23.01.90), many agricultural and forestry areas were affected by pyroclastics deposition. Analysis of ashes and lapillís were performed in order to know if this materíals could represent a potential danger to the agriculture of the zone. Results indicate, according the wearthering rate of pyroclastics, that some nutrients, i.e., N, P, Ca, K, Mg will be incorporated to the soils and will have a beneficial effect to the agriculture. However, dueto the relatively scarse deposition of ashes and the high rainfall (1 ,900 - 2,000 mm per annum), the effect of pyroclastics showers on the soíls will be ephemeral. The content offluoride ofsoils and pastures was not abnormal.

Keywords: pyroclastics, volcanic soils, volcanic eruption.
1 Estación Experimental La Platina (INIA), Casilla 439, Correo 3, Santiago. Chile,