Volcanic ash is known to present hazards to aviation, infrastructure, agriculture, and human and animal health. Airborne ash coats the exteriors of aircraft, enters modern jet engines and melts while coating the interior parts thus causing damage and failure. With support from the National Science Foundation, Volcanologist Dork Sahagian and his colleagues are learning more about the aerodynamic properties of ash, and how long different sizes and shapes stay in the atmosphere. They use a wind tunnel to study how ash travels in the atmosphere during and after volcanic eruptions. They want to develop ways to predict when and for how long damaging ash will fill the skies, and when it’s safe to fly again.