Taiwan makes plate tectonics study breakthrough

2015/08/20

A research team from Taiwan recently made a new discovery relating to the underthrusting of continental crust during orogeny, shedding new light on the decadeslong debate over how mountain belts on the island were formed.

Conducted by five researchers from the Institute of Earth Sciences at Academia Sinica, as well as Department of Geosciences and Institute of Oceanography at National Taiwan University, the study was published in the Aug. 14 issue of prestigious U.S.-based journal Science.

First author Huang Tzu-ying, a doctorate student at NTU, said given Taiwan’s complicated topography and locality at convergent continental plates, the island is an excellent candidate to test various theories of crustal deformation.

“Over the past 40 years, researchers have been debating whether mountain building in Taiwan can be best explained by the thin-skinned model—where deformation takes place mainly in the upper crust—or the thick-skinned model, which suggests that basement rocks are also involved in the process.”

According to Huang, both conceptual models explain only part of the phenomena, and that the real mechanism remains uncertain given the difficulty in making direct deep-crust observations to test the theories. “But by measuring surface waves derived from ambient seismic noises, we developed a hybrid model that has aspects of both theories,” she said.

It was found that the upper crust of Taiwan is dominated by collision-related compressional deformation, while the lower crust is defined by convergence-parallel shear deformation. The two-layer deformation defines the role of subduction in the formation of the island’s mountain belt.

Huang said the study has important implications for understanding how the crust deforms in collisional orogens, and may inspire a re-examination of other mountain belts. “It could also open up new frontiers for further study.”

Source: Taiwan Today (http://taiwantoday.tw/ct.asp?xItem=233955&ctNode=413)