Agung Harijoko
Jurusan Teknik Geologi Fakultas Teknik, Universitas Gadjah Mada

Published : 22 Documents

Found 2 Documents
Journal : Indonesian Journal on Geoscience

Identifikasi Gunung Api Purba Karangtengah di Pegunungan Selatan, Wonogiri, Jawa Tengah Abdissalam, Rus; Bronto, Sutikno; Harijoko, Agung; Hendratno, Agus
Indonesian Journal on Geoscience Vol 4, No 4 (2009)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (2041.022 KB) | DOI: 10.17014/ijog.v4i4.85


DOI: 10.17014/ijog.v4i4.85Karangtengah area in the southeastern part of Wonogiri Regency, is part of the Southern Mountains which is wholly composed of Tertiary volcanic rocks. Nevertheless, the eruptive centre of these volcanic rocks is still unknown. Based on an integrated study that comprises geomorphology, stratigraphy, structural geology, petrology, alteration, and mineralisation the existence of Karangtengah paleovolcano can be identified. The paleovolcano was formed below sea water, basaltic in composition, and it was part of a volcanic island arc during the time. Volcanogenic minerals are found in the central facies containing Fe, Cu, Pb, and Zn.
Estimated Emplacement Temperatures for a Pyroclastic Deposits from the Sundoro Volcano, Indonesia, using Charcoal Reflectance Analyses Harijoko, Agung; Ayu Safira Mariska, Nanda; Anggara, Ferian
Indonesian Journal on Geoscience Vol 5, No 1 (2018)
Publisher : Geological Agency

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (9517.546 KB) | DOI: 10.17014/ijog.5.1.1-11


DOI: 10.17014/ijog.5.1.1-11This study applies the charcoalification measurement method to infer the emplacement temperature of pyroclastic flow deposits erupted from the Sundoro Volcano, Indonesia. This pyroclastic flow partially covered the Liyangan archeological site, a site where Hindu temples were constructed approximately 1,000 years ago. Five samples of charcoal collected from this area were analyzed for reflectance and elemental composition. Charcoalification temperatures were determined based on mean random optical reflectance values (Ro) plotted on published Ro-Temperature curves. Charcoalification temperatures were also estimated using a published formula based on the charcoal’s hydrogen to carbon (H/C) ratio. These two methods for determining pyroclastic flow deposition temperatures indicated that the pyroclastic deposits that entombed the Liyangan archeological site ranged from 295° to 487°C when they were deposited. This study used very simple, rapid, precise, and low-cost methods of charcoalification temperature measurement to infer the emplacement temperature of a pyroclastic deposit. This estimation procedure could be applied widely to predict emplacement temperatures in volcanic area in Indonesia to enhance volcanic hazard mitigation.