[1] These peaks lie just west of a large crustal fracture or structural rift that forms a long, narrow depression passing southeast across the isthmus from the Golfo de Fonseca to the Río San Juan.

[1] Surrounding the lakes and extending northwest of them along the rift valley to the Golfo de Fonseca are fertile lowland plains highly enriched with volcanic ash from nearby volcanoes.

[1] Although periodic volcanic eruptions have caused agricultural damage from fumes and ash, earthquakes have been by far more destructive to life and property.

[1] These rugged mountains are composed of ridges 900 to 1,800 meters high and a mixed forest of oak and pine alternating with deep valleys that drain primarily toward the Caribbean.

[1] The eastern slopes of the highlands are covered with montane rain forests and are lightly populated with pioneer agriculturalists and small communities of indigenous people.

[1] These lowlands are a hot, humid area that includes coastal plains, the eastern spurs of the central highlands, and the lower portion of the Río San Juan basin.

[1] Fertile soils are found only along the natural levees and narrow floodplains of the numerous rivers, including the Escondido, the Río Grande de Matagalpa, the Prinzapolka, and the Coco, and along the many lesser streams that rise in the central highlands and cross the region en route to the complex of shallow bays, lagoons, and salt marshes of the Caribbean coast.

[1] The tierra caliente, or "hot land", is characteristic of the foothills and lowlands from sea level to about 750 meters (2,461 ft) of elevation.

[1] During the rainy season, Eastern Nicaragua is subject to heavy flooding along the upper and middle reaches of all major rivers.

[1] In addition, heavy rains (called papagayo storms) accompanying the passage of a cold front or a low-pressure area may sweep from the north through both eastern and western Nicaragua (particularly the rift valley) from November through March.

[1] Hurricanes or heavy rains in the central highlands where agriculture has destroyed much of the natural vegetation also cause considerable crop damage and soil erosion.

[1] In 1988, Hurricane Joan forced hundreds of thousands of Nicaraguans to flee their homes and caused more than US$1 billion in damage, most of it along the Caribbean coast.