The well-studied Cascadia subduction zone has enriched our general understanding of global subduction zones. This Elements issue explores the interconnected set of processes that link geodynamics, tectonics, and magmatism at depth and the surface expressions of these processes, which shape the landscape and give rise to natural hazards in the Cascadia region. This issue also addresses the impact of subduction zone processes on human populations using cultural records, and reviews the state of knowledge of Cascadia while highlighting some key outstanding research questions.