Parícutin and El Jorullo both rose in an area known for its volcanoes. Called the Trans-Mexican Volcanic Belt, the region stretches about 700 miles (1,120 km) from east to west across southern Mexico. The eruptive activity deposited a layer of volcanic rock some 6,000 feet thick, creating a high and fertile plateau. During summer months, the heights snag moisture-laden breezes from the Pacific Ocean; rich farmland, in turn, has made this belt the most populous region in Mexico.