Cerro Azul (Ecuador volcano)
Encyclopedia
Cerro Azul is a shield volcano
on the south western part of Isabela Island
in the Galápagos Islands
, the name translates from Spanish as blue mountain. There is a strato volcano with the same name in Chile
.
At a height of 1689 m (5,541 ft) it is the second highest peak in the Galapagos and due to its topographic prominence
of over 1500 m (4,921 ft) it is categorised as an ultra
.
The volcano is one of the most active in the Galapagos, with the last eruption between May and June 2008.
which creates a hotspot
of volcanic activity away from plate boundaries where islands then form above it, similar to process that has created the Hawaiian islands. Cerro Azul is at the edge of the upwelling with steep drop offs in the ocean to the West, while the sea is shallower to the east of Isabela Island.
Cerro Azul is one of six coalescing volcanoes on Isabela Island: Ecuador, Wolf
, Darwin, Alcedo
, and Sierra Negra
. Cerro Azul is shaped like a large upturned soup bowl and like the other volcanoes on Isabela Island has a large caldera its one at 4x5 km across is one of the smallest. The caldera shows evidence of collapse following eruptive episodes and reaches a depth of 450 m to 650 m below the rim of the caldera, only Wolf Volcano in the Galapagos is as deep. The volcano is 34 by 22 km at maximum and has a volume of 172 km3. It has steep upper slopes of between 12 and 30 degrees. The shape of the volcano is affected by the sharp ocean drop off to the west where this flank of the volcano slopes steeply to the ocean.
Historical eruptions date back to 1932, but the volcano has had a number of active periods since then in 1940, 1943,1949, 1951, 1959, 1968, 1979, 1998 and most recently in 2008. It is estimated that the surface of the volcano is young, less than 5000 years old and it is estimated that the volcano is about 350,000 years old. The age of Cerro Azul is similar to Sierra Negra and Alcedo and their positioning is not believed to be related to plate movement over the magma plume but instead an interaction between the plume and the lithosphere.
The 2008 eruption began in May and included a fissure eruption on the south east flank of the volcano; the eruption in 1998 had also included fissure eruptions on this part of the volcano. The fissure eruptions resulted in lava flowing 10 km (6 mi) from the fissure. There was also an eruption within the caldera. A second fissure opened lower down the slope in early June.
Analysis of the lavas on Cerro Azul show a range of tholeiitic to alkalic basalts and are unlike the neighbouring Sierra Negra or Alcedo volcanoes
A study published in 2006 showed that there was continuous expansion of the volcano prior to and after the eruption in 1998. This expansion would have been due to the emplacement of magma into the magma chamber.
of giant tortoise
on the island is Geochelone nigra vicina, this subspecies is dome shelled and has an overlapping range with the subspecies on the neighbouring Sierra Negra Volcano, Geochelone nigra guntheri, which is a saddleback tortoise. They Cerro Azul tortoises were not affected by the 2008 eruption although the 1998 eruption did force the National Park authorities to move tortoises by land and helicopter. Other tortoises were killed in that eruption, either from lava or associated fires.
Shield volcano
A shield volcano is a type of volcano usually built almost entirely of fluid lava flows. They are named for their large size and low profile, resembling a warrior's shield. This is caused by the highly fluid lava they erupt, which travels farther than lava erupted from more explosive volcanoes...
on the south western part of Isabela Island
Isabela Island
Isabela Island may refer to:*Isabela Island *Isabela Island...
in the Galápagos Islands
Galápagos Islands
The Galápagos Islands are an archipelago of volcanic islands distributed around the equator in the Pacific Ocean, west of continental Ecuador, of which they are a part.The Galápagos Islands and its surrounding waters form an Ecuadorian province, a national park, and a...
, the name translates from Spanish as blue mountain. There is a strato volcano with the same name in Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
.
At a height of 1689 m (5,541 ft) it is the second highest peak in the Galapagos and due to its topographic prominence
Topographic prominence
In topography, prominence, also known as autonomous height, relative height, shoulder drop , or prime factor , categorizes the height of the mountain's or hill's summit by the elevation between it and the lowest contour line encircling it and no higher summit...
of over 1500 m (4,921 ft) it is categorised as an ultra
Ultra prominent peak
An ultra prominent peak, or Ultra for short, is a mountain with a topographic prominence of or more. There are a total of roughly 1,524 such peaks in the world. Some are famous even to non-climbers, such as Mount Everest, Aconcagua, and Mount McKinley , while others are much more obscure...
.
The volcano is one of the most active in the Galapagos, with the last eruption between May and June 2008.
Geology
The Galapagos Islands are believed to be formed from a mantle plumeMantle plume
A mantle plume is a hypothetical thermal diapir of abnormally hot rock that nucleates at the core-mantle boundary and rises through the Earth's mantle. Such plumes were invoked in 1971 to explain volcanic regions that were not thought to be explicable by the then-new theory of plate tectonics. Some...
which creates a hotspot
Galápagos hotspot
The Galápagos hotspot is a volcanic hotspot in the East Pacific Ocean responsible for the creation of the Galapagos Islands as well as three major aseismic ridge systems, Carnegie, Cocos and Malpelso which are on two tectonic plates. The hotspot is located near the Equator on the Nazca Plate not...
of volcanic activity away from plate boundaries where islands then form above it, similar to process that has created the Hawaiian islands. Cerro Azul is at the edge of the upwelling with steep drop offs in the ocean to the West, while the sea is shallower to the east of Isabela Island.
Cerro Azul is one of six coalescing volcanoes on Isabela Island: Ecuador, Wolf
Volcán Wolf
Volcán Wolf is the highest peak in the Galapagos Islands and is situated on Isabela Island and reaches and is the highest point in the Galapagos Islands...
, Darwin, Alcedo
Alcedo Volcano
Alcedo Volcano is one of the six coalescing shield volcanoes that make up Isabela Island in the Galapagos. The remote location of the volcano has meant that even the most recent eruption in 1993 was not recorded until two years later...
, and Sierra Negra
Sierra Negra (Galápagos)
Sierra Negra is a large shield volcano at the South eastern end of Isabela Island in the Galapagos that rises to an altitude of 1124m. It coalesces with the volcanoes Cerro Azul to the west and Alcedo to the north...
. Cerro Azul is shaped like a large upturned soup bowl and like the other volcanoes on Isabela Island has a large caldera its one at 4x5 km across is one of the smallest. The caldera shows evidence of collapse following eruptive episodes and reaches a depth of 450 m to 650 m below the rim of the caldera, only Wolf Volcano in the Galapagos is as deep. The volcano is 34 by 22 km at maximum and has a volume of 172 km3. It has steep upper slopes of between 12 and 30 degrees. The shape of the volcano is affected by the sharp ocean drop off to the west where this flank of the volcano slopes steeply to the ocean.
Historical eruptions date back to 1932, but the volcano has had a number of active periods since then in 1940, 1943,1949, 1951, 1959, 1968, 1979, 1998 and most recently in 2008. It is estimated that the surface of the volcano is young, less than 5000 years old and it is estimated that the volcano is about 350,000 years old. The age of Cerro Azul is similar to Sierra Negra and Alcedo and their positioning is not believed to be related to plate movement over the magma plume but instead an interaction between the plume and the lithosphere.
The 2008 eruption began in May and included a fissure eruption on the south east flank of the volcano; the eruption in 1998 had also included fissure eruptions on this part of the volcano. The fissure eruptions resulted in lava flowing 10 km (6 mi) from the fissure. There was also an eruption within the caldera. A second fissure opened lower down the slope in early June.
Analysis of the lavas on Cerro Azul show a range of tholeiitic to alkalic basalts and are unlike the neighbouring Sierra Negra or Alcedo volcanoes
A study published in 2006 showed that there was continuous expansion of the volcano prior to and after the eruption in 1998. This expansion would have been due to the emplacement of magma into the magma chamber.
Wildlife
The subspeciesSubspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
of giant tortoise
Galápagos tortoise
The Galápagos tortoise or Galápagos giant tortoise is the largest living species of tortoise, reaching weights of over and lengths of over . With life spans in the wild of over 100 years, it is one of the longest-lived vertebrates...
on the island is Geochelone nigra vicina, this subspecies is dome shelled and has an overlapping range with the subspecies on the neighbouring Sierra Negra Volcano, Geochelone nigra guntheri, which is a saddleback tortoise. They Cerro Azul tortoises were not affected by the 2008 eruption although the 1998 eruption did force the National Park authorities to move tortoises by land and helicopter. Other tortoises were killed in that eruption, either from lava or associated fires.