(Source: Yangmingshan National Park Headquarters)

Datun volcanic fumarole

Besides the thirteen hot spring and fumarole areas where great clouds of geothermal steam rush out of fumaroles of all sizes encrusted with yellow sulfur crystals -- other typical geological features of the Tatun volcano group are crater lakes and geological faults.

Volcanoes can be classified as cones and tholoids. Volcanic cones are formed by the piling up of lava flows and pyroclastic rocks around the volcanic crater. Mt. Cising is a good example of this type of volcanic cone. At an elevation of 1120 meters above sea level, it is the highest peak in Yangmingshan National Park. This is one of the younger volcanoes in the park, and it has the most intact conical shape.

When large volcanoes are formed, molten lava may flow out of the hillside and form another smaller volcano nearby, known as a parasitic volcano. Mt. Miantain, for example, is a parasitic volcano of Mt. Datun, and Mt. Shamao is a parasitic volcano of Mt. Cising.

Lava with high silica content is highly viscous and will form a low round hill like an inverted bell, known as a tholoid volcano. Volcanic activity in the Yangmingshan area tailed off after the formation of Mt. Shamao some 300,000 years ago, leaving the various signs of post-volcanic activity we see today.