SOIL CLASSIFICATION AT FAMILY CATEGORIES FROM TERTIARY VOLCANIC ROCK FORMATION WITH DIFFERENT TYPE OF LITHOLOGY: A CASE STUDY OF INDONESIA

This research aims to classify the characteristic of soil that development from Tertiary Volcanic Rock Formation for land management to increase soil bearing capacity. A field survey, rock and soil morphological description, and laboratory analysis carried out to describe soil properties and weathering grade of rock. Weathering grade of lithology characterized by Santi method and clay minerals identification with X-ray Diffractometer. The Soil classified with soil taxonomy key USDA 2014. The andesite and volcanic breccia lithologies have the II-III-IV grade of weathering from bottom to the soil surface. The soil was acidic to slightly acidic and the CEC was 18.69-24.25cmol+ /kg. The CEC value influenced by the presence of kaolinite more than montmorillonite, but base saturation was higher than >35% and formed cambic horizon on soil from volcanic breccia. The soil development from andesite lava volcanic classified asVitrandic Dystrudepts and volcanic breccia classified as Mixed Ruptic-Alfic Dystrudepts. The Mixed Ruptic-Alfic Dystrudepts showed the presence of 16.8% of montmorillonite and 11.1% of vermiculite minerals that indicate a high potential to decrease soil bearing capacity and triggering a deep landslide in this area.