A bank of clouds may make it look like Castleton Tower is floating on an island in the sky. But it’s actually deeply rooted in the earth, connected even to the rumbles of far-off ocean waves and earthquakes. U geologists say that vibrations carried through bedrock cause the tower near Castle Valley, Utah, to sway ever so slightly at about the same rate as a heartbeat. Studying how this and other natural rock formations move helps researchers keep an eye (and ear) on their structural health, including how human-made vibrations such as helicopter flights or truck traffic might affect seemingly unmovable rocks. Click here to learn more.