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Volcano Cosigüina

Cosigüina Volcano is located 80 kilometers northwest of the city of Chinandega. It stands as a watchtower on the peninsula, which bears the same name, enters the Pacific Ocean enclosing the southern Gulf of Fonseca. This volcano erupted on the 20th to 23rd of January 1835, on the last day there was an explosion with a force of exceptional size that caused the collapse of the structure of the volcano on its own base, leaving a vast hollow over 2 kilometers in diameter and 600 feet deep at the bottom of which formed the current crater lake.

The ancient forests around the volcano were charred, but it was evident the rapid ecological recovery, in 40 years, the forest returned to its former luxuriance and biological wealth, which was preserved almost intact until the middle of this century.

The richness of its flora and fauna attracted the attention of loggers and hunters, whose presence and activity forced the state to declare the area as a wildlife refuge since 1958; in 1983 it was declared as a Nature Reserve and Volcano Cosigüina today is one of the protected areas of Nicaragua as part of the biological corridor of the Gulf of Fonseca, which is also composed of protected areas in Honduras and El Salvador.
The reserve is located in the center of the peninsula, distinguishing two zones: one plain, where agriculture and population is concentrated, and another in the center, where lies the volcanic structures with steep slopes with soils unsuitable for agriculture, accounting for forest resources and wildlife. In this area there are wildlife species such as White Collar Sahin of (Tayassu tajacu) and the Scarlet Macaw (Ara macao) that practically do not exist elsewhere in the Pacific.

The underground aquifer of the peninsula is small and is isolated from the aquifer known as León-Chinandega, so it depends only on the rainfall in the area and the infiltration of the them, which is largely dependent on the maintenance of coverage plants in the protected area.

The peninsular position makes from this protected area and its buffer zone are poorly connected to the more "continental" land area to the south, ie the other volcanoes of the Andes. However, so far t has not been found any endemicity among the studied species.


Volcano Cosigüina was originated during the Pleistocene by the superimposition of pyroclastics and lavas, in turn mounted on a base that experienced an uneven lift dipping to the east during the Holocene that can be seen in the strata which form the so-called raised Cosigüina Cliffs (Farallones del cosiguina) of 100 meters high and on the top of them were discovered fossils of foraminifera estimated age of no more than 10,000 years (Incer et al, 2000).

After several centuries of apparent calm the volcano became active on January 20, 1835. According to the American volcanologist Howel Williams, who made the only study a century after the eruption, he considered the eruption as Vesuvian, produced by a sudden effervescence of magma trapped inside the volcano, with such a force that the entire summit was virtually pulverized and blown by the blast, estimating about 10 km3 of material ejected during the event, was considered by Williams as "the most violent eruption in the Americas in historic times", although other studies estimate the ejecta from 3 to 5 km3 . The eruption began with a large column of gas and ashes that darkened the sky three days around the Gulf of Fonseca, as well as northern and western Nicaragua. Then it started several explosive phases with continuous shaking and loud rumblings that were heard throughout Central America and the West Indies, having reached the ashes southern Mexico. At the end of the eruption it was the collapse of the entire structure on its own base (Incer et al, 2000).

Today Cosigüina is considered to be a volcanic building with a shield in the central part of the boiler which is opened, a hole diameter of 2,500 meters and 700 meters depth, in the bottom later emerged the current crater lake. The sides and base of the cone is covered by pyroclastic deposits, which were aerially deposited notably thick during the eruption, as well as colluvial sediments carried by currents to the lowlands (Incer et al, 2000).

The crater lake of Cosigüina occupies the bottom of the boiler that was formed after the eruption and collapse of the volcano in 1835. The water mirror is about 160 meters above the sea level and 700 meters below the top edge of the caldera, with an area of 133 hectares. The greenish blue color of its waters is due to the presence of certain blue green algae that are adapted to the sulfuric waters that are carried by the hydrothermal emissions emanating from inside. The steepness of the rocky walls makes the crater almost inaccessible, although in some places there are trees that grow suspended between cracks and crevices (Incer et al, 2000).

The ancient forests around the volcano were burned during the eruption and buried by volcanic ashes, killing all the wildlife that inhabited it. The same fate had the cattle and the young men who were taking care of two farms near the volcano.