(Source: Yangmingshan National Park Headquarters)

Hot Springs and Fumaroles

Hot springs require three conditions for their formation: an underground supply of hot water, pressure to force it upwards, and deep fissures or cracks in the rock so it can penetrate to the surface.

In Yangmingshan National Park, the distribution of hot springs and fumaroles is controlled by a sandstone formation that underlies the 13 geothermal areas. All of Yangmingshan's geothermal activity is confined to a narrow strip between Beitou and Zhishan about 18 kilometers long and 3 kilometers wide. The most active steam vents are those at Tahuangtsui, Siaoyoukeng, Macao, Dayoukeng, Ssuhuangtzuping and Kengtzuping.

Forces inside the earth's crust cause rock to rupture. If rocks on both sides of the fracture move relative to each other, a fault is formed. When surface water seeps down and is heated by an underground heat source, most of it is retained inside porous rock but a small amount rises to the surface along the fissure or fault and emerges as a hot spring. If the water temperature is above boiling point, the water vaporizes underground and emerges as fumarolic steam.

Yangmingshan's popular hot springs can be divided into three types according to their chemical composition. First are the acid sulfate (white sulfur) hot springs, such as those at Tahuangtsui, Jhuzihhu, Ssuhuangtzuping and Kengtzuping. Next are acid sulfate chloride (green sulfur) hot springs, such as the ones at Xin Beitou. Last are neutral iron-bearing hot springs, such as those at Tingpichiao and Lengshuikeng; these are cooler and mostly consist of indirectly heated groundwater.

Enjoying a good soak in a steaming, silky-smooth hot spring set amidst beautiful natural scenery is one of life's greatest pleasures. No wonder so many people make the trip up to Yangmingshan on a regular basis. They wouldn't miss their daily hot spring dip for the world!