Post by willi1 on Jul 25, 2018 12:34:13 GMT
Colliding continents and cracks in the Earth’s crust make for some remarkable scenery in western China.
About 300 million years ago, the Tien Shan mountains began forming when the Tarim Block—a mass of land that was once part of Australia—collided with Eurasia. During the Mesozoic Era (252 to 66 million years ago), a series of island arcs (curved chains of volcanic islands) continued to smash into Eurasia, further building the mountain range. About 80 million years ago, the Indian subcontinent started colliding as well, triggering a whole new phase of mountain building.
When land masses collide, the pressure can create what geologists call “fold and thrust belts.” Slabs of sedimentary rock that were laid down horizontally can be squeezed into wavy anticlines and synclines. Sometimes the rock layers break completely, and older layers of rock pile up on top of younger layers. This type of break, known as a thrust fault, formed the series of ridges seen in the image, called Piqiang Fault.
