Thursday, May 27, 2010

El Jorullo is a cinder cone volcano in Michoacán, central Mexico, on the southwest slope of the central plateau, 33 miles (53 kilometers) southeast of Uruapan. Jorullo has four smaller cinder cones which have grown from it. The vents of Jorullo are aligned in a northeast to southwest direction. Lava from these vents cover nine square km around the volcano.

El Jorullo is one of two known volcanoes 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. Parícutin is about 50 miles (80 km) northwest of this volcano. El Jorullo originated on September 29, 1759. Earthquakes occurred prior to this first day of eruption. Once the volcano started erupting, it continued for 15 years until in 1774. El Jorullo didn’t develop on a corn field like Parícutin did, but it did destroy what had been a rich agricultural area. It grew approximately 820 feet from the ground in the first six weeks.

The eruptions of El Jorullo 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 Jorullo ever had, and was the longest cinder cone eruption known.