Taiwan lies on the adjacent area between the Eurasia Tectonic Plate and the Philippine Sea Plate; seismic activities are therefore frequent. In the later part of the Paleozoic era, Taiwan was a geosyncline, or a subsiding linear trough that was formed by the accumulation of sedimentary rocks. A combination and interactions of sedimentation, metamorphism, the uplifting of land plates and the subduction of others for an extended period of time caused the now complex geological structure. Taiwan’s last uplift took place two to three million years ago between the Pliocene and the Pleistocene period. Due to the Penglai Orogeny and the subsquent movements of the earth’s crusts, the island of Taiwan rose from the ocean.
Yushan National Park is situated in the central area of the island of Taiwan. The oldest geological terrane for the park and Taiwan is composed of the Tananao Complex, which itself is composed of metamorphed basement rocks and is located on the east side of the Central Mountain Range.
Furthermore, due to tectonic activity, the rock strata are fragile; causing fault lines, joints and foldings, among other geological features, to be rather prominent. As a result of metamorphism, rock foliations such as cleavage and schistosity have developed. Consequently, the rocks are weakened in their ability in withstanding the process of weathering. Awe inspiring cliffs and percipice such as the Great Precipice, Scree slope beneath the foot of the main peak, the Laonong Fault scarps between the main peak and Batongguan, Fuzi Cliff and Guanshan Cliff are formed as a result. On the rock walls along the Southern Cross Island Highway and the Yushan Scenic Highway (Provincial Highway 18), spectacular foldings and fault lines can be observed. It is a great place for exploring geological wonders, though caution should always be exercised for falling rocks.