Al Vincent Ramos, BSc
A. Ramos1, D.L. Flores1
1Department of Geology, Negros Oriental State University, Dumaguete City, Negros Oriental, Philippines
Valencia, Negros Oriental, is a region renowned for its geological complexity, shaped by the interplay of volcanic, tectonic, and geothermal processes. The landscape is dominated by volcanic rock formations, notably basalt and andesite, which reflect the area’s dynamic tectonic history and its proximity to the Negros volcanic belt. The Southern Negros Geothermal Field serves as a key site for understanding fractured geothermal systems and tectonic evolution, with geothermal features—including fumaroles, hot springs, and geothermal reservoirs—underscoring the region’s active geological environment.
Field investigations focused on several significant geological landmarks: the Puhagan Dike, Okoy River, sulfur vents, and Pulangbato Falls. The Okoy River valley exposes older volcanic formations, providing insights into the region’s volcanic past, while the Puhagan Dike represents intrusive igneous activity associated with regional tectonics. Sulfur vents and geothermal springs, particularly around Pulangbato Falls, highlight ongoing hydrothermal activity; the falls are notable for their striking columnar basalts, which display evidence of folding and deformation due to tectonic forces.
Stratigraphic and lithologic research has documented a sequence of volcanic and sedimentary formations in Valencia, ranging from the Cretaceous Basak Formation to Quaternary andesitic volcanics. This progression traces the geological evolution from ancient volcanic rocks and basalt, through the Puhagan Volcanics and Okoy Sedimentary Formation, to more recent volcanic deposits. These layers record a history of episodic volcanic activity, sedimentation, and tectonic deformation that has shaped the landscape over millions of years.
Tectonic and seismic studies have further elucidated the evolution and seismicity of the Philippine Mobile Belt, within which Valencia is situated. The region’s geology is marked by convergent plate boundaries, notably the Negros and Sulu Trenches, which have played a fundamental role in the development of volcanic arcs and the accumulation of extensive volcanic deposits, including lava flows, pyroclastic materials, and widespread ash layers. Over time, these processes have significantly shaped the physical landscape and geological character of the area.
The interplay between geology and environment in Valencia is evident in its rugged terrain, mineral-rich geothermal springs, and the development of eco-tourism attractions. This synthesis of literature and field studies provides a comprehensive understanding of Valencia’s geological framework, emphasizing its importance for sustainable development, natural resource management, hazard assessment, and ecological diversity within Negros Oriental.