Few of us have any conception of the enormous timescales in our planet's long history, and this narrow perspective underlies many of the environmental problems we are creating for ourselves. The passage of nine days, which is how long a drop of water typically stays in Earth's atmosphere, is something we can easily grasp. But spans of hundreds of years-the time a molecule of carbon dioxide resides in the atmosphere-approach the limits of our comprehension. Our everyday lives are shaped by processes that vastly predate us, and our habits will in turn have consequences that will outlast us by generations. Timefulness reveals how knowing the rhythms of Earth's deep past and conceiving of time as a geologist does can give us the perspective we need for a more sustainable future.Marcia Bjornerud shows how geologists chart the planet's past, explaining how we can determine the pace of solid Earth processes such as mountain building and erosion and comparing them with the more unstable rhythms of the oceans and atmosphere. These overlapping rates of change in the Earth system-some fast, some slow-demand a poly-temporal worldview, one that Bjornerud calls "timefulness."