Ometepe Island, Lake Nicaragua
11.53 N, 85.62 W
summit elevation 1700 m
Concepción volcano and its twin neighbour Madera form the island of Ometepe in Lake Nicaragua. It is an almost perfect steep cone built on a thick sequence of sediments beneath Lake Nicaragua. It has been described as having a "clay foot".
The volcano is experiencing gravity induced spreading due to a weak clay base. The volcano rises 1600 m above Lake Nicaragua. Prevailing trade winds send tephra deposits west of the cone of Concepcion, while lavas mainly extends east. Tephra deposits are 50 m think at Moyogalpa, 8 km west of the crater. There is almost no tephra on the coastal plain north and south of the volcano.
The summit of Concepcion volcano has increased in height by 100 m in recent times due to eruptive activity. Most of the visible upper part of the cone was built between 1883 and 1977. Forest is scarce in the volcano, and is not well developed compared to neighbouring Maderas volcano. There is a striking lack of faulting at Concepcion volcano compared to surrounding areas.
Small ash eruptions occurred at Concepción volcano on 9th February, 8th April, 22nd April, and 10th July.
A small ash eruption occurred at the volcano on 1st September 2006. On 21st September three explosions produced an ash emission which was visible from the city of Granada 56 km NW of the volcano.
An ash eruption on 28th July deposited ash on the town of Moyagalpa (9 km W of the summit) and on the mainland settlements west of the volcano, at San Jorge, Buenos Aires, Potosí, and Belén.
On 27th December, ash emissions reached 300 m above the crater. On 29th of December, ash fell at San Jorge, 25 km SW of Concepción.
Small ash eruptions occurred in December 1984. On 2nd January 1985, a strong emission of tephra occurred at Concepción volcano. Ashfall damaged tobacco and sesame crops, and fell on the towns of Esquipulas, Los Angeles, and Moyogalpa. Eruptions occurred between 4th February and 8th April 1986. Vegetation was killed for 3 km on the western side of the volcano. Some people evacuated houses above the village of San José, 8 km SW of the crater.
Pre 1977 Eruptions
Historic activity at Concepción volcano before 1977 consisted of mild Strombolian or small Plinian eruptions of basalt to silicic andesite about every 10 years. Lava flows occurred about every 20 years. This activity has built most of the visible part of the cone. Since 1977, only minor ash eruptions and degassing has occurred.
Explosions and ash plumes were reported from the crater in July 2007.
2007, 2006, 2005, 1999, 1985-86, 1984-85, 1983, 1982, 1978, 1977, 1973-74, 1963, 1962, 1961, 1957, 1951-55,1948-50, 1944-45, 1935, 1929, 1928, 1921-26, 1918-19, 1907-10, 1902, 1891, 1884-86, 1883, 1800?