The structure of Arima Onsen

The surface of the earth is covered with a hard plate (a layer of rock), which is divided into seven large plates and several small plates. Since the Japanese archipelago is located at the collision of four plates, it is prone to large earthquakes and is one of the world's leading volcanic archipelago. There are three types of volcanoes, but the Japanese archipelago falls under the type of volcano called the island arc. There are many volcanoes in the Tohoku region, and there are three types of volcanoes from the Pacific side: the Kitakami Mountains, the Ou Mountains, and the Echigo Mountains. However, there are no volcanoes in the Kinki region. Why is there no volcano in the Kinki region when the Philippine Sea plate is subducting under the Japanese archipelago on the south side of the Kii Peninsula? .. Magma is not possible because it has not reached 110km. It is presumed that this is torn off by the type and epicenter of the earthquake. Arima Onsen is just above the 60km point. Shirahama Onsen is similar to Arima Onsen, but the depth is 30km. Since the thickness of the land plate is 25km, the hot springs in Shirahama spring from the border, while the hot springs in Arima are already 30km deep. In other words, the difference in the amount of ingredients contained in the upper mantle is the difference between the hot springs in Arima and Shirahama. As a result of observing the earthquake that occurs in the fault, the fault is 14km deep. Since the thickness of the land plate is 30 km, the land plate 16 km below the fault is a mass of rock. When boiling stew or curry, the igneous dykes that penetrate the bedrock of the land plate from the upper mantle are less dense than other bedrock, just as bubbles rise from the bottom of the pan, and this part is like a tunnel. It is thought that it is connected to the fault in the town of Arima. The upper mantle 60km below is a world of high temperature and pressure. It is thought that Arima's hot springs melt a special substance, become supercritical water with both liquid and gas properties, rise, and reach the surface of the earth at once around this dike. This tunnel is located in the center of Arima. A hot spring that is rare in the world emerges from the fault that connects to the tunnel. This hot spring is called "Arima-type hot spring".

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