The thermal valley at the source of Peitou Creek contains sulfuric acid, iron, barium, radium, and other base elements. As the creek water flows between 90 and 390 meters from the source, the water temperature drops enough to cause these elements to crystallize on the gravel that lines the creek bed.
由於北投溪源頭的地熱谷含有硫酸鉛、鋇、鐳等礦物元素，當北投溪水在離源頭九十到三百九十公尺的地方，因水溫降低致使礦物結晶附著在河床礫石上而形成。