张掖国家地质公园，甘肃，中国 Zhangye Danxia National Geopark, Gansu, China (© TONNAJA/Getty Images)

张掖国家地质公园，甘肃，中国 Zhangye Danxia National Geopark, Gansu, China (© TONNAJA/Getty Images)

行走在彩虹岩石上 Walking a rocky rainbow

国际岩石日

7月13日是国际岩石日。为什么要给岩石设立一个节日呢？因为自石器时代以来，岩石就在人类历史中扮演着重要角色。它们是人类最早的工具，也是自然的记录，包裹着古代生物的化石，也留下了地质变化的印记。中国张掖丹霞国家地质公园的彩虹山就是一个很好的例子。这里的沉积岩经过数百万年的风化和侵蚀，最终形成了这片色彩斑斓的风景，红、橙、黄、紫各色疏密相生，组合有序。变质岩、沉积岩、火成岩等等各种各样的岩石帮助形成了我们今天所生活的世界。

International Rock Day

International Rock Day, on July 13, celebrates these hardy heroes, which have played a big part in human history since at least the Stone Age. They served as humanity's first tools and as nature's journals, protecting ancient fossils and documenting changes caused by geological processes.

Our homepage image shows Zhangye National Geopark's Rainbow Mountains in China, an incredible landscape created over millions of years. Those colorful layers are formed of sedimentary sandstone rock. Iron oxide gave the rock its predominately rusty hue, while other oxides tinted the various layers brown, yellow, and green. Sandstone and minerals that were once layered on top of each other were lifted and distorted by tectonic movement, revealing those colorful stripes. And that is not the end of this geological tale. This unique landscape continues to change, as wind and water erosion sculpts new pillars and ravines. No matter what your favorite category of rock is—metamorphic, sedimentary, or igneous—rocks of every kind helped build the world we live in today.