El Jorullo
From Wikipedia, the free encyclopedia
El Jorullo is a cinder cone volcano in Michoacán, central Mexico, on the SW slope of the central plateau, 33 mi/53 km SE of Uruapan (also know to be located in an area known as the Michoacan-Guanajuato volcanic field). El Jorullo has four smaller cinder cones which have grown from it. The vents of El Jorullo are aligned in a northeast to southwest direction. Lava from these vents cover nine square km around the volcano. Later eruptions produced lavas that had higher silica contents making them thicker than the earlier basalts and basaltic andesites lavas. El Jorullo's crater is about 1,300 by 1,640 ft (400 by 500 m) wide and 490 ft (150 m) deep.
El Jorullo is one of two known volcanos to have developed in Mexico in recent history. The second, born about 183 years later, was named Parícutin after a nearby village that it eventually destroyed. Paricutin is about 50 miles (80 km) southwest of El Jorullo.
El Jorullo was born on September 29, 1759. Earthquakes occurred prior to this first day of eruption. Once it began erupting, it didn't quit for 15 years. El Jorullo didn’t develop on a corn field like Paricutin did, but it did destroy what had been a rich agricultural area. Jorullo grew 820 ft (250 m) from the ground in the first six weeks. The eruptions were phreatic and phreatomagmatic. They covered the area with sticky mud flows, water flows and ash falls. All but the youngest lava flows were covered by this ash fall. Later eruptions were magmatic with neither mud nor water flows. This 15 year eruption was the only one El Jorullo ever had, and was the longest cinder cone eruption known. It last erupted in 1958, nearly 200 years after it began to develop.
Paricutin and El Jorullo both rose in an area known for its volcanoes. Called the Mexican Volcanic Belt, the region stretches about 700 miles from east to west across southern Mexico. Geologists say that 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. Though the region already boasted three of the country's four largest cities: Mexico City, Puebla, and Guadalajara (the area around Paricutin, some 200 miles west of the capital), it was still a peaceful backwater inhabited by Tarascan Indians in the early 1940s. Its gently rolling landscape, in a zone that had experienced almost no volcanic activity during historic times, was one of Mexico's loveliest. Although hundreds of extinct cinder cones rose around the small valleys, the only eruption in human memory had been that of distant El Jorullo.
