The conversion of rock to soil prepares Earth's surface for erosion by wind, water, gravity, and life. Together these agents wear down hills and mountains even as the land rises up under the stress of tectonic forces in the crust. Meanwhile, weathering liberates nutrients from minerals and disaggregates rock into regolith, generating hospitable substrates for life. Over the last two decades, geochemists, geomorphologists, and soil scientists have increasingly used cosmogenic nuclides to quantify how fast soils are made, modified, and finally swept away in hilly and mountainous landscapes around the world. These studies are revolutionizing our understanding of soils and their role in feedbacks that shape Earth's surface, influence overlying ecosystems, and modulate climate over millions of years.