Mount Tai rises abruptly from the vast plain of central Shandong, and is naturally endowed with many scenic sites. Geologically, it is a tilted fault-block mountain, higher to the south than north, and is the oldest and most important example of the paleo-metamorphic system representative of the Cambrian Period in eastern China. Referred to as the Taishan Complex, it comprises magnetized, metamorphic, sedimentary rock and an intrusive mass of various origins that were formed in the Archean Era 1700-2000 million years ago. Subsequently, in the Proterozoic Era, the Taishan region began to rise, becoming part of the continent by the end of the era. Uplift continued until the middle of the Cenozoic Era. The gneiss which emerged in the Taishan region is the foundation for all of North China. Cambrian strata, fully emerged in the north, are rich in fossils. Six streams flow from the summit, their water renowned for its extremely low mineral content, slight acidity (pH = 6.3) and relatively high oxygen content (6.4 milligrams per liter (mg/l)).