2010 Guatemala City sinkhole and donation centers for victims of the storm were opened across the country. According to the Office for the Coordination of Humanitarian Affairs (OCHA), schools in Guatemala were to be closed until at least June 4. Immediately after the sinkhole's collapse, there were plans to fill it in with a soil cement made from cement, limestone, and water known locally as "lodocreto" ("mudcrete"). This substance was also used to fill in the 2007 Guatemala City sinkhole. However, another technique, which geologists call the graded-filter technique, in which the sinkhole is filled with successive layers of boulders, smaller rocks, and gravel,
Collapse of the World Trade Center both cases, the section of the building that had been damaged by the airplanes failed, which allowed the floors above the impact zone to fall onto the undamaged structure below. As the collapse progressed, dust and debris could be seen shooting out of the windows several floors below the advancing destruction, caused by the sudden rush of air from the upper levels. The first fragments of the outer walls of the collapsed North Tower struck the ground 11 seconds after the collapse started, and parts of the South Tower after 9 seconds. The lower portions of both buildings' cores (60