Sinkhole urban areas due to water main breaks or sewer collapses when old pipes give way. They can also occur from the overpumping and extraction of groundwater and subsurface fluids. Sinkholes can also form when natural water-drainage patterns are changed and new water-diversion systems are developed. Some sinkholes form when the land surface is changed, such as when industrial and runoff-storage ponds are created; the substantial weight of the new material can trigger a collapse of the roof of an existing void or cavity in the subsurface, resulting in development of a sinkhole. Sinkholes tend to occur in karst landscapes. Karst
Henry A. Schade obtain and exploit German science and technologies in areas immediately behind the front lines of fighting in Europe. As allied ground forces gained ground, Schade and his scientists would rush into the void left behind advancing forces to study the equipment and weaponry employed by the Germans. The United States Naval Technical Mission in Europe was particularly interested the capture and study of rocketry and all things naval as German ports and bases were wrested from Hitler's forces. Schade initially headquartered the Mission in Paris, but soon the Mission was constantly on the move as allied forces advanced more and