Distribution of Hot Springs of the World

Field: Earth and Planetary Sciences (Physical Sciences)

We can defined, from the geothermal point of view, that the hot spring is a spring heated by the subsurface heat sources. One of main heat sources in the ground is the explicit or implicit intrusive magma of high temperature and the other is a heat source corresponding to the terrestrial heat flow of non volcanic area. The former is the most normal one which follows a conception that the distribution of hot springs agrees with the zone of recent volcanic activity. On the other side, it needs to make the hot spring by the latter heat source, the special system in which the cold groundwater infiltrates into deep ground, beeing heated by normal ground temperature and ascending with less cooling up to the earth surface. But, generally, the infiltration of cold groundwater causes the cooling of the ground, so that, to keep continuously heating groundwater, there must be compensative heat flow from deeper ground in the area. This means that under the area of higher heat flow is expected very deeply intruded magma, or the area is corresponding to the ascending part of the convection current in the mantle. We believe, therefore, that the distribution of hot springs of the world has the great geothermal significances.It has been well known that Japan, New Zealand, California and Alaska are abundant areas of hot springs, and are located in the circumpacific volcanic zone. Likewise, there are many hot springs along the mediterranean volcanic zone. Therefore, it has been generally considered that zone of hot springs coincides with the volcanic zone on the global scale. But we have not had yet any map of distribution of hot springs of the world.In this paper we will show distribution of hot springs of the world based on more than five thousand hot springs data which we have got hitherto, and are summarized in Table 1. General tendency of the distribution compared with crustal structure of the earth, and the significance of the hot springs as a natural phenomena will be discussed from the standpoint of the earth science.The distribution of hot springs of some main areas are shown in Figs. 1 to 13. The distribution of the world is shown in Fig. 14, and its schematic figure is in Fig. 15. From these figures, it appears that though there are many areas where the zones of the hot springs coincide with the volcanic zones, many hot springs are also in the non volcanic areas, where the hot spring zones are corresponding to the zones of the folded mountains. This is easily appreciated by comparing Fig. 14 with Fig. 16 showing tectonic structure of the world. These facts are also verified by Fig. 17 of European tectonic structure and Fig. 20 of American tectonic structure. There, hot springs are located in the recent orogenic zones.Finally, we can come to reach a conclusion that the distribution of hot springs is reflected not only in volcanic activity of the earth surface but in the essential tectonic structure which governs the distribution of volcanoes or the geothermal pattern of the earth. Thus the distribution of hot springs has the most important meaning in the geothermy.Numbers of geothermal area including boiling springs, fumaroles and solfataric fields are about 330 in all the world, and their distribution is shown in Fig. 21 which is very similar to the distribution of the volcanoes.