Modern civilization is subject to gradual environmental, social, economic, and political transformations as well as to sudden changes that can fundamentally alter its prospects. This article examines a key set of such fatal discontinuities by quantifying the likelihood of three classes of sudden, and potentially catastrophic, events—natural disasters (the Earth's collision with nearby asteroids, massive volcanic eruptions and mega-tsunami generated by these events, as well as by huge landslides); viral pandemics; and transformational wars—and by comparing their likelihood with other involuntary risks (including terrorism) and voluntary actions and exposures.