Morphological characterization of Taal Main Crater Lake and Lake Pinatubo, in comparison with Lake Caliente, Poas Volcano and Lake Towada, Japan, and their implications on the surface processes, hydrothermal activity and lake chemistry

Volcanic lakes are often classified based on the underlying processes and the dynamics of the volcanic system. Some are classified based on their acidity, the activity of the magmatic-hydrothermal system underneath, and some classifications are based on the dominant elemental composition of the lake water. But there has been a lack of classification scheme that is attributed to the morphological characteristics of the volcanic lakes. Establishing and proposing a classification based on morphology and morphometry of volcanic lakes would greatly contribute to our understanding of the physical geology and surface processes related to volcanic lake systems. The Taal Main Crater Lake and Lake Pinatubo are both representative of a crater lake and caldera lake, respectively, that are hosted in an active volcanic system. Characterization of the volcanic lakes is done based on their morphometric measurements on the planimetric and cross-sectional aspect, wherein ellipticity ratio, irregularity index and shape parameters are considered in the classification. Measurements for Lake Caliente, Poás Volcano in Costa Rica and Lake Towada, Towada Volcano in Japan were also obtained for comparison. Disparity was seen on the planimetric shapes of the four studied volcanic lakes which can be attributed to the different dynamic processes, such as its open and close-type system and frequency in volcanic activity. Similar results were observed on the crater lakes of Taal Volcano and Poás Volcano, while contrasting plots were seen on the caldera lakes of Lake Pinatubo and Lake Towada. Lake Pinatubo has a surface and basal width ratio close to 1 which can be an indicator of a balanced outflow and inflow rate in the volcanic lake system. A need for introducing and establishing a new classification scheme for volcanic lakes is of utmost priority, especially for active volcanic lake systems that may have limited access due to its hazardous nature. The ability to classify volcanic lakes and interpret their mechanisms remotely would greatly provide an avenue for further development of volcanic lake studies.