El Jorullo
Encyclopedia
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
(also known to be located in an area known as the Michoacán-Guanajuato Volcanic Field). Coordinates are 18°58′26.43"N 101°43′2.97"W (18.974008, -101.717492), about 6 miles (10 kilometers) east-northeast of La Huacana
. Its current elevation is 1320 metres (4,331 ft). El Jorullo has four smaller cinder cones which have grown from its flanks. 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 basalt
s and basaltic andesite
lava
s. El Jorullo's crater is about 1,300 by 1,640 feet (400 by 500 meters) wide and 490 feet (150 meters) deep.
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 El Jorullo.
El Jorullo was born on September 29, 1759. Earthquakes occurred prior to this first day of eruption. Once the volcano started erupting, it continued for 15 years...eventually ending 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 (250 meters) from the ground in the first six weeks. The eruptions from El Jorullo were primarily 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 from El Jorullo were magmatic with neither mud nor water flows. This 15 year eruption was the longest one El Jorullo has had, and was the longest cinder cone eruption known. Lava flows can still be seen to the north and west of the volcano. The eruption had a VEI
of 4.
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 kilometers) 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 Parícutin, some 200 miles west of the capital), it was still a peaceful backwater inhabited by Tarascan Indians in the early 1940s.
Cinder cone
According to the , Cinder Cone is the proper name of 1 cinder cone in Canada and 7 cinder cones in the United States:In Canada: Cinder Cone In the United States:...
volcano
Volcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...
in Michoacán
Michoacán
Michoacán officially Estado Libre y Soberano de Michoacán de Ocampo is one of the 31 states which, with the Federal District, comprise the 32 Federal Entities of Mexico. It is divided in 113 municipalities and its capital city is Morelia...
, central Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
, on the southwest slope of the central plateau, 33 miles (53 kilometers) southeast of Uruapan
Uruapan
Uruapan is a city and municipality in the west-central part of the Mexican state of Michoacán. The city is the municipal seat of the municipality...
(also known to be located in an area known as the Michoacán-Guanajuato Volcanic Field). Coordinates are 18°58′26.43"N 101°43′2.97"W (18.974008, -101.717492), about 6 miles (10 kilometers) east-northeast of La Huacana
La Huacana
La Huacana is a municipality in the south-central part of the Mexican state of Michoacán. The municipality has an area of 1,952.60 square kilometres and is bordered to the north by the municipalities of Nuevo Urecho and Ario, to the east by Turicato, to the south by Churumuco and Arteaga, and to...
. Its current elevation is 1320 metres (4,331 ft). El Jorullo has four smaller cinder cones which have grown from its flanks. The vents of El Jorullo are aligned in a northeast to southwest direction. Lava
Lava
Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...
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 basalt
Basalt
Basalt is a common extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. It may be porphyritic containing larger crystals in a fine matrix, or vesicular, or frothy scoria. Unweathered basalt is black or grey...
s and basaltic andesite
Basaltic andesite
Basaltic andesite is a black volcanic rock containing about 55% silica. Minerals in basaltic andesite include olivine, augite and plagioclase. Basaltic andesite can be found in volcanoes around the world, including in Central America and the Andes of South America. Basaltic andesite is common in...
lava
Lava
Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...
s. El Jorullo's crater is about 1,300 by 1,640 feet (400 by 500 meters) wide and 490 feet (150 meters) deep.
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
Paricutín
Parícutin is a cinder cone volcano in the Mexican state of Michoacán, close to a lava-covered village of the same name. It appears on many versions of the Seven Natural Wonders of the World...
after a nearby village that it eventually destroyed. Parícutin is about 50 miles (80 km) northwest of El Jorullo.
El Jorullo was born on September 29, 1759. Earthquakes occurred prior to this first day of eruption. Once the volcano started erupting, it continued for 15 years...eventually ending 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 (250 meters) from the ground in the first six weeks. The eruptions from El Jorullo were primarily phreatic
Phreatic
The term phreatic is used in Earth sciences to refer to matters relating to ground water below the water table . The term 'phreatic surface' indicates the location where the pore water pressure is under atmospheric conditions...
and phreatomagmatic. They covered the area with sticky mud flows, water flows and ash falls. All but the youngest lava
Lava
Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...
flows were covered by this ash fall. Later eruptions from El Jorullo were magmatic with neither mud nor water flows. This 15 year eruption was the longest one El Jorullo has had, and was the longest cinder cone eruption known. Lava flows can still be seen to the north and west of the volcano. The eruption had a VEI
Volcanic Explosivity Index
The Volcanic Explosivity Index was devised by Chris Newhall of the U.S. Geological Survey and Stephen Self at the University of Hawaii in 1982 to provide a relative measure of the explosiveness of volcanic eruptions....
of 4.
Parícutin and El Jorullo both rose in an area known for its volcanoes. Called the Trans-Mexican Volcanic Belt
Trans-Mexican volcanic belt
The Trans-Mexican Volcanic Belt also known as the Transvolcanic Belt and locally as the Sierra Nevada , is a volcanic belt that extends 900 km from west to east across central-southern Mexico...
, the region stretches about 700 miles (1,120 kilometers) 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
Pacific Ocean
The Pacific Ocean is the largest of the Earth's oceanic divisions. It extends from the Arctic in the north to the Southern Ocean in the south, bounded by Asia and Australia in the west, and the Americas in the east.At 165.2 million square kilometres in area, this largest division of the World...
; 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
Mexico City
Mexico City is the Federal District , capital of Mexico and seat of the federal powers of the Mexican Union. It is a federal entity within Mexico which is not part of any one of the 31 Mexican states but belongs to the federation as a whole...
, Puebla
Puebla, Puebla
The city and municipality of Puebla is the capital of the state of Puebla, and one of the five most important colonial cities in Mexico. Being a planned city, it is located to the east of Mexico City and west of Mexico's main port, Veracruz, on the main route between the two.The city was founded...
, and Guadalajara
Guadalajara, Jalisco
Guadalajara is the capital of the Mexican state of Jalisco, and the seat of the municipality of Guadalajara. The city is located in the central region of Jalisco in the western-pacific area of Mexico. With a population of 1,564,514 it is Mexico's second most populous municipality...
(the area around Parícutin, some 200 miles west of the capital), it was still a peaceful backwater inhabited by Tarascan Indians in the early 1940s.