The Costa is a relatively narrow strip of desert along the coast. It is widest in the north, where much of the land consists of shifting sand and dunes. Elsewhere the Costa is generally a mere ribbon of barren land, with broader areas at river deltas, many of which are agricultural oases. The strip is not continuous; in some areas the mountains extend to the sea. Lima, the nation’s capital, and many of Peru’s largest cities are located in this region, on rivers from the Sierra.
The Sierra is a broad highland region, east of the Costa. It consists of rugged Andes mountain ranges, lofty volcanoes, plateaus cut by deep canyons, and a number of intermontane basins. Peru’s highest peak, Huascaran, is a snowcapped volcano rising 22,205 feet (6,768 m) above sea level.
The Montana, east of the Sierra, is a heavily forested lowland region that takes up more than half of Peru’s area. Most of the Montana lies in the Amazon Basin and is still unsettled, mainly because of its remote location and dense tropical jungle.
The large rivers of Peru begin in the Andes and flow through the Montana; all are part of the Amazon system.
Among them are the Ucayali and Maranon, the two chief headstreams of the Amazon, and the Putamayo, Napo, Pastaza, Huallaga, Apurimac, Urubamba, and Madre de Dios. The Amazon proper begins just above the city of Iquitos. A number of rivers, all of them short, drain from the Andes to the Pacific. Most of them dry up during part of the year, but their waters are extremely important for irrigation along the coast.
Lake Titicaca, the largest freshwater lake in South America, lies in the Sierra, partly in Peru and partly in Bolivia. It occupies part of a high plateau region called the Altiplano and is about 12,500 feet (3,810 m) above sea level.
Although Peru lies just south of the Equator, much of the country does not have a tropical climate. Along the coast, the temperatures are mild and there is little rainfall, mainly because of the influence of the cold Peru (Humboldt) Current offshore. Lima, for example, averages 73° F. (23° C.) in January and 61° F. (16° C.) in July and normally receives only about two inches (50 mm) of rain each year.
Except for humid eastern slopes, the Sierra is a relatively dry region. Temperatures range from temperate to frigid, depending on elevation. Only in the Montana is there a humid tropical climate. Here rainfall is heavy, and temperatures are usually high throughout the year.