Yulian Saputra’s scientific contributions

This research aims to explain the reasons for choosing andesite igneous rock as building material from Hindu-Buddhist kingdoms. The research method in this article uses four stages of historical research, namely; heuristic techniques, source criticism techniques, interpretation techniques, and historiography techniques. Data sources were collected through primary and secondary data. The four stages of this historical research method together with secondary primary data are then analyzed using a combination of historical geography to obtain an in-depth study. The results of the research illustrate that the use of andesite igneous rock was used for temple buildings, statues, relief sculptures, and writing from Pallawa to Ancient Java. The choice of andesite igneous rock during the Hindu-Buddhist kingdom was based on the quality of the rock. The quality of this andesite rock has high artistic value, gray in color, hard, chemical composition and specific texture that can be carved. The chemical composition is 57% -63% silica content with 6% alkali metal oxide content. The silica content of andesite igneous rock makes this rock material resistant to weathering.

This study describes the geomorphological natural setting that became the guerrilla event of General Sudirman through literature studies, concepts, theories, and relevant previous research results. The study area of this research covers the central and southern zones of Java Island. The research analysis used descriptive analysis with the help of satellite image interpretation. This study indicates that the guerrilla route covers a geomorphological area that stretches across three provinces in Java Island. The geomorphological background is the karst landscape of Gunung Kidul and the volcanic slopes of Mount Wilis.