Understanding the causes and consequences of natural hazards is one of the grand challenges of the Helmholtz Research Field "Earth & Environment". Research Unit 4 studies natural hazards and associated risks and contributes to mitigation solutions with a broad interdisciplinary team from GFZ and cooperating partner institutions. We investigate fundamental processes leading to single and cascading hazards, model their observed and expected consequences, develop methods to quantify and forecast hazard and risk and develop early warning systems. We use our broad monitoring networks and observatories to validate our models. We place a strong emphasis on outreach activities and delivering products and services relevant to society. Research Unit 4 contributes exclusively to the topic “Natural Hazards” of the Program “Geosystem: The changing Earth”.