ナショナルジオグラフィックさんのインスタグラム写真 - (ナショナルジオグラフィックInstagram)「Photo by Pete McBride @pedromcbride / Wind, water, light, and time—elements that create the world around us. Arches like these form when salt layers below tons of sandstone flow upwards, sending cracks through the rock above them. Then, just enough rainfall seeps in and slowly dissolves the minerals holding the rock together, eventually creating a cavity. Cold winters freeze the water collected between the rock layers, which expand and crack further. The process takes a long time, but patience is rewarded with the formations dotting the Southwest. For more from the western U.S., follow @pedromcbride. #publiclands #nature #nightsky #arches #petemcbride」2月16日 16時39分