THE CHARACTERISTICS OF-VOLCANO-LAHARS AS THE RESPONSE OFDIFFERENT TYPES OF HOLOCENE ERUPTION

Merapi volcano as one of most active strato-volcano tipes in the world, at the historical of the eruption had some different types of eruptions, as explosive and effusive eruption. Effusive type of eruption creates lava spills, lava dome and pyroclastic avalanches while explosive eruption leads to pyroclastic falls and pyroclastic flow. Lahar is type of mudflow composed of debris and angular block mostly from a volcano. In Mt. Merapi, lahars can affect the people widely, causing not only loss of lives but also damage and loss of property and livelihood assets. The morphological features of Merapi Volcano consist of four slopes that are bordered by slope breaks. Each slope and slope break are reflecting their dominant rocks formation, their morphological functions to the volcanic deposits, and past historical processes. Based on its characteristics of explosive and effusive eruptions as well as processes of lahar flows, Mt. Merapi is formed by five units of lava, four pyroclastics and five units of lahars. The stratigraphy of Merapi Volcano can be ctagorised into 5 stages: New Merapi, Young Merapi Mature Merapi, Old Merapi, and Pre Merapi. In adherence to the post positivism paradigm that requires verification and/or validation of the probabilistic approaches through parametric as well as non-parametric statistical tests, it profess that Mt. Merapi during the Neogene period experienced evolution of types eruption. The main chemical compositions TiO2, Fe2O3, MgO, CaO, and K2O as well as the rims of hornblende structure distinguish the types of eruptions during that period. Changes of pyroclastic character are determined by the gigness and forms of components in the sizes of block, pebbles and gravels, not by giant component. The changes in sizes and forms of pyroclastic components are not in order and not in correlation with the distance of deposits. Lahar characters change in oderly fashion,(negatively) in medium to very strong correlation with the distance of deposits. The correlations get stronger during the lahar flow in the one watershed; meanwhile , the forms of lahar components are not in oderly fashion and not in correlation with the distance of sediment deposits. Giant component is constitutes the main significant part to be managed in the adaptation of lahar risk reduction. For that purpose, a research on the geology of volcano with the further details analysis on lahar components is highly necessary. The positions of lahar as the responses to types of eruptions become a significant part in the efforts in developing a geological map, distater prone zone map as well as Merapi eruption disaster risk map. The method can subsequently be applicable for mapping of other volcanoes Kata Kunci/ Key-words: Merapi. Lahar, post-positivism