Pennsylvania’s Ridge-and-Valley Appalachians

iss074e0315614 (Feb. 13, 2026) --- The icy Susquehanna River merges with the Juniata River as it flows across the wintry landscape of Pennsylvania’s Ridge-and-Valley Appalachians. This geological structure was formed from folded sedimentary rock and erosion patterns roughly 250 to 480 million years ago during the late Paleozoic Era. The International Space Station was orbiting 260 miles above the Keystone State when this photograph was taken. Credit: NASA/Chris Williams