On September 19, 1985, a powerful earthquake strikes Mexico City and leaves 10,000 people dead, 30,000 injured and thousands more homeless. At 7:18 in the morning, the residents of Mexico City were jolted awake by an 8.1-magnitude earthquake, one of the strongest to ever hit the area. The effects of the quake were particularly devastating because of the type of ground upon which the city sits. Mexico City is on a plateau surrounded by mountains and volcanoes. The plateau region was covered by lakes in ancient times. As the aquifer under the city has slowly drained, it has been discovered that the city sits atop a combination of dirt and sand that is much less stable than bedrock and can be quite volatile during an earthquake. The quake on September 19 was centered 250 miles west of the city but, due to the relatively unstable ground underneath the city, serious shaking lasted for nearly 3 minutes. The prolonged ground movement caused several old hotels, including the Regis, Versailles and Romano, to crumble. A building at the National College of Professional Education fell, trapping hundreds of students who were attending early-morning classes. Many factories in the city, built with shoddy materials, also could not stand. Further, the tremors caused gas mains to break, causing fires and explosions throughout the city. When the damage was finally assessed, 3,000 buildings in Mexico City were demolished and another 100,000 suffered serious damage.