Nindiri cones with the latter the host of the Santiago, Nindiri, San Pedro and, confusingly, Masaya craters.
Across Lago Xolotlán and some 45-50 km NW of Managua lies the Momotombo volcano and Volcanic Field with Volcán Cerro Negro, Central America’s youngest (April 1850) and one of the most active volcanoes in Nicaragua almost immediately to its WNW. Momotombo volcano is one of Nicaragua’s most familiar landmarks. It is a somma volcano, meaning it has grown on the edge of the caldera of a mainly collapsed, previous edifice; Monte Galán. It began growing about 4.5 kA BP at the SE end of the Marrabios Range and the symmetrical cone has now attained a height a.s.l. of 1,297 m with a prominence in excess of 1,100 m. If we only take into account the portion above the 400-m isoline, the edifice has a volume on the order of 3.5 km3. In addition to this, there are the products of the geothermal volcanic field on the ESE flank as well as lava flows from Momotombo that have flowed down the NW flank into the 4-km-wide Monte Galán caldera to consider. Also, it has formed a 391-m-high island; Isla Momotombito, offshore in Lake Managua. In all, the volcanic products of Momotombo over the past 4½ millennia is in excess of five cubic km. Consequently, Momotombo has a long record of mainly strombolian eruptions punctuated by occasional larger explosive activity with at least fifteen eruptions since the arrival of the Conquistadores. The most recent in 1905 produced a lava flow that travelled from the summit to the lower NE base of the volcano.
There are two facts to keep in mind concerning Momotombo. First, volcanism seems to be migrating in the direction of Managua; from Monte Galán via Momotombo and into Lago Xolotlán, which is a cause for grave concern in the case of a large-ish, submarine eruption. Second, the copious amounts of juvenile magma fed into and mixing with the crust to form the andesitic lavas. At the very minimum, the rate is in excess of a cubic km per thousand years.
Looking at the map, there are further areas of major volcanism in the vicinity of Managua. Apart from the already mentioned Masaya Caldera and Momotombo, there’s the 6 x 7 km wide Apoyo caldera (Laguna de Apoyo) about 10 km SE of the Masaya Caldera and 30 km from Managua, the collapse of which has been assigned a radiocarbon date of 23 kA BP. Volcanism at Apoyo began about 90 kA BP and the caldera was formed by two plinian eruptions that produced the Upper and Lower Apoyo tephras separated in time by about 100 to a few hundred years. Much closer to the Nicaraguan capital, to the NW and across a bay of Lago Xolotlán, lies the Reserva Natural Península de Chiltepe with the twin, 2½ km crater lakes or calderas Apoyeque and (Laguna de) Xiloá. In the GVP, it is listed as Apoyeke.
Located on the Chiltepe Peninsula, Apoyeque is part of the Chiltepe pyroclastic shield volcano, one of three large ignimbrite shields on the Nicaraguan Volcanic Front. As volcanoes go, it is rather unimpressive as in spite of a base diameter in excess of 10 km, the Apoyeque crater walls do not even attain 400 m a.s.l. with the highest point , “Volcán Chiltépe” – a lava dome on its eastern edge, almost reaching 500 m a.s.l. In fact, it is somewhat reminiscent of Taal minus much of the caldera lake. The summit crater or caldera is 2.8-km wide and 400 m deep, the floor of the lake-filled caldera lies near sea level. Immediately to the SE of Apoyeque lies the 2½ x 3 km lake-filled maar crater Xiloá. On the surface, it is a beautiful setting for recreation for the citizens of Managua, but once you take a look at the history of activity, a very disturbing picture emerges, especially given its location so close to the Nicaraguan capital.
The Nejapa Volcanic Field
From the Xiloá crater and through the western part of Managua City runs the Nejapa-Miraflores fault, along the eastern edge of the Managua Graben between the Mateare and Nejapa-Miraflores fault. It is a volcanic field in its own right – the Nejapa Volcanic Field (NVF). It consists of at least 30 volcanic structures of which at least