Geodiversity Assessment of Widodaren Spring: A Treasure Trove Site for Bromo Tengger Volcano’s Future Geopark

Abstract The Bromo Tengger Volcano in Indonesia, a prominent geotourism spot, features the notable Widodaren Spring within its caldera, originating from the inactive Widodaren Vulcanic Cone. This study evaluated the geodiversity of Widodaren Spring through field and laboratory analyses and identified geodiversity elements by assessing their potential educational utility (PEU), potential touristic utility (PTU), and degradation risk (DR). Widodaren Spring is unique, showcasing rocks, hydrogeology, and landscape elements. This location is composed of pyroclastic fall deposits and pyroclastic surges, which characterize the products of volcanic activity on this volcano and provide a Sea of Sand Caldera landscape. Field and laboratory data indicate that this spring is genetically topographic-stratigraphic and hydrochemically calcium-chloride-type. The high levels of sulfate-chloride in the groundwater samples suggest the influence of volcanic gases from the nearby Bromo Volcanic Cone. Rainwater infiltration at the upper cone (2400-2560 meters) flows through lapilli layers serving as aquifers, with tuff and lapilli tuff layers below being impermeable to semi-permeable. Geodiversity assessments revealed a high educational utility potential (PEU) of 310 points, medium tourist utility potential (PTU) of 260 points, and low degradation risk (DR) of 135 points. The high PEU score was attributed to the site’s unique geological elements, making it valuable for education and science. The medium PTU score reflects its location in a national park, limiting accessibility but protecting it from human-caused damage. Potential natural damage may arise from weathering and volcanic eruptions on Mount Bromo. In conclusion, Widodaren Spring possesses significant geodiversity value with great potential for education and tourism, alongside a minimal risk of degradation. This site is a treasure trove for the future Bromo-Tengger Volcano geopark.