Sedimentary Coastal Area
The Sedimentary Coastal Area is not a homogenous unit despite the fact that, as the name implies, it is composed mainly of sedimentary formations. The soil composition found within the Sedimentary Coastal Area varies greatly. Within this area we can see three major subunits:
The Northwestern plains encompass the departments of Leon and Chinandega, although the volcanic range running down the middle of the plains is, naturally, excluded from this sub classification. The altitude of the plains varies from sea level to one hundred meters above the sea. They are composed mostly of sedimentary rocks, product of the erosion that wind and water have caused on both the Central Region to the east and the volcanic range in the middle.
The Coastal Belt is located between the Tamarindo and Escalante rivers, corresponding to the area west of the Diriamba Highlands. It is sectioned by numerous rivers originating in the Highlands. It is the product of marine sediments that emerged with the highlands.
The Rivas Isthmus is itself subdivided into two smaller sections: the hills parallel to the Pacific Ocean, which attain a maximum elevation of only 525 meters; and the plains along the coastline of Lake Nicaragua, at barely thirty-one meters above sea level.
San cristobal and Momotombo Volcanoes
Quaternary Volcanic Region
The Quaternary Volcanic Region can also be subdivided into three distinct areas: the Maribios Volcanic System; the Diriamba Highlands; and the Lakes. This last one is an independent system that includes volcanic formations (extinct craters and hills, as well as lagoons), and the two lakes. While the Maribios Volcanic System seems to start in the far northwestern tip of the country with the Cosigolcano, this is technically incorrect. The Cosigns actually belongs to the Salvadoran system. The Maribios volcanic range starts more accurately with the Chonco (although it is also acceptable to name the San Cristobal volcano) and ends with the Momotombo volcano. The Maribios volcanic range extends for seventy kilometers. The average height of these mountains is of little more than one thousand meters, but one would have to take into consideration that the Cerro Negro volcano is of very recent origin (in fact, one of the youngest volcanoes in the planet, having emerged only in the mid 1800s) and is growing very rapidly. The system itself is followed by the Chiltepe peninsula on the shores of Lake Managua and finally ends with the Cuapes hills.
There are small plains along the lakes that separate the Diriamba Highlands from the Maribios system, including the Managua-Tipitapa area. The Diriamba Highlands system is formed by the Managua Hills (Sierras de Managua) and the Los Pueblos Plateau (Meseta de los Pueblos). Towards the southwest we find the Masaya and Mombacho (with an altitude of 1,345 metres) volcanoes, both active. Despite its low height of only 635 metres, the Masaya Volcano is one of the most active in the world. It has five craters within a cauldron of 8 x 11 km, although only the Santiago crater is currently active. Up until recently, a lake of lava could be seen at the bottom of the crater. The Masaya Volcano has had a long history of non-eruptive degassing, releasing large amounts of toxic gasses with daily emissions of between 300 and 5,000 tonnes of SO2 and HCl, among others, that can be seen even from space. As a consequence of such large emissions, the soil structure of the area affected is highly acidic and vegetation growth has been stunted all the way from the volcano itself to the Pacific coast.
These volcanic formations continue on to the islands of Zapatera, an ancient volcano now extinct, and Ometepe, formed by the Concepcion (1,610 metres) and Maderas (1,394 metres) volcanoes. The Volcanic plains are part of the Lakes system and lie immediately east of the Managua Hills and Pueblos Plateau. They form a narrow corridor stretching from Managua to Granada. The lakes are two large depressions that were formed when the volcanic chain of the Pacific Highlands emerged from the Pacific Ocean. The volcanic eruptions activated the fault lines that run from the Gulf of Fonseca to Costa Rica and these, in turn, formed the depressions. The lakes have never contained seawater. Rather, they were filled with water coming from the rivers from the Central Highlands whose paths towards the Pacific were diverted by the emergence of the mountains to the west.