**7. Final remarks and future perspectives**

In the previous sections, we have briefly outlined some of the main aspects that need to be considered when working in paleovolcanic terrains. Probably, the most important is the fact that volcanic activity has not fundamentally changed over time (uniformitarianism), so that we can confidently assume that the volcanic processes and products that we observe at present are the same as those represented in the geological past. Therefore, their characterization and interpretation may be carried out in the same way. This observation, however, also allows us to consider another important aspect of volcanic activity, which is that, despite the existence of certain broad similarities, each volcanic area may have particular characteristics, which suggest that it should be studied independently. The criteria that must be taken into account when studying an ancient volcanic terrain should be as similar as possible to the ones used in recent volcanic areas. At present, it is not enough to give a good description of the different volcanic or volcano-sedimentary deposits, an essential step in any volcanological study, but they must be interpreted in terms of their volcanological significance and their influence on associated depositional environments. Therefore, the same should be applied to the study of paleovolcanic terrains.

Many paleovolcanic terrains are associated with important mineral deposits (e.g., Kurokos, in Japan [98, 99]; the Pyrite Belt of the Iberian Peninsula [40, 100]). Volcanic areas represent regions with a high thermal flux and the existence of hydrothermal fluids, many of them directly associated with the magmatic source, which means a high possibility for the accumulation of mineralizing elements. Likewise, volcaniclastic materials can constitute important hydrocarbon reservoirs (e.g., [42, 101]). Diagenetic changes of fresh volcanic deposits can reduce their permeability; however, the dissolution of volcaniclastic materials can contrastingly increase permeability and increase reservoir quality. The study of paleovolcanic terrains in terms of modern volcanology may also provide results that are quite helpful in the study of recent terrains with similar characteristics, where such processes may be inferred, yet not observed directly due to the lack of deep erosion and tectonics. Similarly, the exploration of high-enthalpy geothermal reservoirs in active volcanic areas can greatly benefit from the study of ancient analogs coming from deeply eroded volcanic terrains where the roots of the volcanic edifices are well exposed and the geometry and distribution of fossil geothermal reservoirs can be observed (e.g., [102–104]).

Another aspect to highlight in the study of ancient volcanic terrains is that they offer a good source of information to analyze plate tectonic evolution and the formation of sedimentary basins (e.g., [105]). In this sense, we can deduce the geodynamic framework in which the basins develop by studying the nature of the associated volcanism. The reconstruction of the position of eruptive vents will give information on the tectonic structure of the basin, since it will allow us to infer the distribution of the fractures through which the magma ascended to the surface; this will thereby provide clues for the reconstruction of the corresponding stress field. Therefore, the presence of volcanic products in the sedimentary record of a basin should not be necessarily considered as an isolated event. Volcanic activity must be interpreted as an effect with the same causes that condition the existence of some sedimentary basins, although on some occasions it can even become the direct cause that conditions their formation, as is the case of some collapse calderas and volcanotectonic depressions (e.g., [106, 107]).

Based on what has been exposed in this contribution, I hope that a clear idea can be drawn for the importance of a correct interpretation of the volcanic episodes that we find in the geological record. A good description of the products generated by these volcanic processes is the first step to be able to understand their true meaning. However, the reconstruction of the volcanic episodes, in terms of their geodynamic framework, volcano-tectonic environment, basin dynamics, and eruptive mechanisms, based on a correct identification and interpretation of deposits, should be the main objective that we must consider when beginning a study of paleovolcanic terrains.
