Where it is and what it carries
The Yangtze Plate covers about 2.2 million square kilometers, or 0.43% of Earth’s surface. It is also known as the South China Plate. On land it carries 15.4% of China, all of Hong Kong and 27.2% of Taiwan. Offshore it includes the wide, shallow continental shelf of the East China Sea and the Taiwan Strait.
The plate is built on old continental crust. Geologists call this crust the South China Block, which formed when two older pieces, the Yangtze Block and the Cathaysia Block, joined in the Neoproterozoic Era. The lower course of the Yangtze River, which gives the plate its name, crosses this stable interior.
What happens at its edges
The longest boundary, 3,791 km, is with the Eurasian Plate on the plate’s western and northern sides in central China. PB2002 classifies most of it as continental rift, with stretches of transform and collision, and the relative speed is about 1.2-1.7 cm/yr.
To the east, a 1,409 km boundary with the Okinawa Plate follows the Okinawa Trough, a back-arc basin that is pulling apart behind the Ryukyu Islands at about 2.1-5.5 cm/yr. In the south, a 906 km boundary with the Sunda Plate is mostly transform and moves at about 1.4-1.5 cm/yr. In the north, a 589 km transform boundary with the Amur Plate moves at only about 0.4 cm/yr.
The fastest edge is short. Along 439 km at Taiwan, the Philippine Sea Plate collides with the Yangtze Plate at about 8.1-8.6 cm/yr. Here the Luzon volcanic arc is crashing into the Chinese continental margin, and the collision has raised Taiwan’s Central Range, where Yushan (Jade Mountain) reaches 3,952 m.
Earthquakes and volcanoes
The interior of the plate is quiet. The dataset lists only 17 earthquakes of magnitude 6.5 or larger since 1900, one of them magnitude 8 or more. The largest, the 1910 Taiwan earthquake (M8.1), struck at about 235 km depth. It and several other large events, such as the 1911 quake near Amami (M7.9, 150 km deep), happened deep beneath the plate’s eastern edge, most likely inside slabs of subducting seafloor.
Shallow quakes are fewer but more damaging. The 1935 earthquake near Taichung, Taiwan (M7.1) caused heavy losses in western Taiwan, and the 1918 earthquake near Shantou on the Guangdong coast (M7.4) was felt strongly across Guangdong and as far as Hong Kong.
Volcanoes are rare. The dataset lists two, both in northern Taiwan: the Tatun Volcano Group just north of Taipei and Kueishantao, a small volcanic island off the northeast coast.
Why geologists separate it
Textbooks usually treat southeastern China as part of the Eurasian Plate. GPS surveys, however, show the South China Block moving east to southeast as a fairly rigid unit relative to Eurasia, partly because the India-Asia collision squeezes crust out of Tibet toward the east. PB2002 therefore draws it as its own plate. Its boundaries are less sharp than those of large plates, and some researchers treat it as a crustal block within Eurasia rather than a true plate.