Application of Red Relief Image Maps as a complementary tool for mapping volcanic areas: The case of the Monte Amiata volcano, Italy

Geological mapping provides the basic knowledge for understanding the eruptive and temporal evolution of a volcanic area. Because of their increasing availability and resolution, Digital Terrain Models (DTMs) are extensively and fruitfully used in volcanology as an additional tool for recognizing and classifying geomorphological features and assisting field survey and mapping tasks. This study focuses on the application of Red Relied Image Maps (RRIMs), derived from a high-resolution 1 m pixel/resolution DTM and complemented and validated with fieldwork, to identify and outline partially hidden volcanic features at an intensely vegetated volcano. We present here the results of the application of this method at Monte Amiata volcano (southern Tuscany, Italy), an effusive, silicic Middle Pleistocene volcano with a massive hardwood forest cover, whereas we identified elongated and plateau-like lava flows at the base of the volcano and coulees and overlapped rounded domes at the top. In addition, we performed a localized Fourier transform (i.e., S-Transform spectral analysis) for determining the dominant frequencies and identifying repeating patterns of the largest lava flows to quantify their surface folding pattern. These analyses were based on differential openness and RRIMs data at different scales (1, 10, and 100 m) and DTMs resolutions (1 and 10 m). We demonstrate that the extensive use of these mapping tools can represent an effective method for recognizing and interpreting otherwise hidden volcanic structures. We suggest that applying DTM-derived parameters should be considered a necessary step for the precise mapping of remote or heavily vegetated volcanic areas.