Formation of Shidao

The materials that make up the Shidao Formation are also very different, some are rough shells, coral sand, some are snails and dragonflies. These creatures first grew in shallow lakes and were lifted up in the crustal movement and became part of the hills.

Affected by crustal movement, some of these strata are horizontal, and some are not necessarily very horizontal, but each dip angle is above 38. Due to the continuous erosion of Shidao by waves from all directions, the island area is getting smaller and smaller and is on the verge of extinction.

Coral limestone, which constitutes a stone island, is eroded by waves and rain, and there are many karst landforms such as small caves, small dissolved holes and root dissolved pipes on the rock wall around the island. For example, in the northern part of the island, there is a dendritic pipeline vertically developed in a 2-meter-thick rock stratum, which is very distinctive.

The sediments that make up Shidao are older than other islands in the South China Sea. According to the survey, at the height of 10 meter, the age of rock strata is mostly around 14000 years, and the oldest is about 23000 years. The platform on the island is relatively young, about 5000 years old, which shows that this platform was formed after the island uplifted. The sediments on the reef plate in front of the island are young, about l700 years old, and formed late. The deposition on the surface of the reef plate continues, and a newer platform is forming. In other words, Shidao uplift has a history of at least 15000 years. This long-term uplift process is also the process of erosion and accumulation of Shidao.

Shidao is the oldest island in Xisha Islands. It has a history of at least 10,000 years and is the highest island in the Xisha Islands. Some people say that Shidao is the "pyramid" of Xisha, saying that it is a pyramid not only because it looks like a pyramid, but also because it has some mysterious mysteries like a pyramid. Most of the islands in Xisha Islands are formed by the accumulation of biological gravel such as corals and shells, and the rocks are relatively loose. Only Shidao is composed of some layered biological sandstones, and the rocks are very hard. But also different from other layered biostones in structure. Generally, the bottom of layered biostones is older than the top, but the rock island is the opposite. This phenomenon of rock island has not been reasonably explained in science.