South America

Andes – the Cordilleras of South America

The Andes, also known as the Cordilleras, are the mighty chain mountains that sweep the entire western edge of South America. They essentially consist of two main lines, the western and the eastern cordilleras. In the highlands in between are plateaus (e.g. Altiplano) or long valleys (e.g. avenue of volcanoes). The plateaus and valleys form the Sierren.

The Cordilleras are home to mighty volcanoes (e.g. Aconcagua, Huascarán, Chimborazo). The Andes are part of the most recent mountain formation era (of the same age as the Alps and the Himalayas), which is not completely finished here (e.g. volcanic eruptions and earthquakes).

Location, extent, division of the Andes

The Andes (Spanish: Cordilleras de los Andes) are the South American part of the mighty mountain range (Spanish: Cordilleras = “chains”), which stretches over 16,000 km in the west of the double continent from North to South, from Alaska to Tierra del Fuego continues in Antarctica as Antarctica. The Andes are the longest fold mountains on earth.

The Andes essentially consist of two main lines running in the same direction, the Eastern Cordilleras and the Western Cordilleras. Between the two are steppe and desert-like highlands enclosed. The Cordilleras are usually close together and together they only reach a width of approx. 150 to 300 km; only in Bolivia is the width about 800 km.

But they can also diverge, as in Colombia, where a central cordiller is inserted. The heights of the Andes rise continuously from north to south to Aconcagua (6959 m), the highest mountain in North and South America, which lies on the border between Argentina and Chile (Fig. 1). Then they quickly fall off until they are lost in the fjords and islands of Tierra del Fuego. Examples of the ups and downs of the heights are the Pico Cristobal Colon (5775 m) in Colombia, the Chimborazo (6310 m) in Ecuador, the Huascarán (6768 m, picture 1) in Peru, the Illimani (6882 m) in Bolivia and the Murallón (3600 m) in Chile. See CountryAAH.

The individual parts of the Andes have different names. They are labeled like the countries in which they are located, e.g. B. Ecuadorian Andes, Peruvian Andes and Bolivian Andes.
To the west, the Andes quickly descend to a narrow, only about 100 km wide coastal plain, mostly called Costa. It is determined by desert-like areas with river oases and deserts (e.g. Atacama Desert).

To the east, the Andes slowly lose height and go over to huge low and mountain countries, which run for about 1000 km to a maximum of 6000 km to the coast of the Atlantic. There are the lowlands of the Orinoco, the Amazon (with 4.5 million km² the largest tropical lowland) and Paraguay/Paraná as well as the mountainous regions of Guiana and the Brazilian highlands.

The Andes are also a watershed between the Pacific and the Atlantic. Powerful rivers such as Orinoco, Amazonas and tributaries of the Paraná arise in the Andes. With a length of 6518 km and a catchment area of 7 million km², the Amazon is the largest river system on earth.

Sao Paulo is the largest city in South America.

Origin of the Andes

The Andean surface forms essentially correspond to their geological structure. In South America there are two different geological units: the young Andean system (mainly tertiary) and the very old Brazilian mass with the Patagonian mass (pre-Cambrian). The border between the two units is approximately the eastern Andean foot. The Andes owe their origin and unity to the recent mountain formation era and are of the same age as the Alps or the Himalayas.

Uneven contrasts in relief, rock and tectonics indicate that older geological links have been incorporated into the chain mountain system. Such old clods are often found between the two Cordilleras, in the so-called Sierra. They were included in the creation of the mountain range.

The Andes are partly made of crystalline material, partly of Mesozoic layered rock, which has been folded, discarded and moved, raised or lowered (Fig. 2). Deep trenches and break-in basins structure the mountain body, fractures penetrate it and make the tectonic overview more difficult. Mighty volcanoes sit on the fault linesthat still work in large numbers. They are a characteristic element of the Andes. The trenches and basins inside and the coastal fringe (Costa) at the Pacific Rim are frequently affected by earthquakes. The edge break on the Pacific is a 7000 m deep sea trench that accompanies the ruggedly falling western cordillera over thousands of km. All of these facts underline the youthful character of the Andes.
The surface shapes of the Andes were especially shaped in the ice age (Pleistocene or Diluvium) and can still be found particularly clearly in the Alpine regions. Then began the continual destruction of the mountains by weathering, erosion and denudation (extensive, leveling-out erosion), which left a different treasure of forms.

Sierra – Highlands between the Cordilleras

The interior of the Andes, the highlands between the Cordilleras, in contrast to the lowlands in the east and the coastal country in the west, is called Sierra. It is very different in its parts. Wide, partially drained plateaus alternate with relatively narrow long valleys. Where the rivers breached the Cordilleras, which is often the case in Ecuador and Peru, the associated, closed mountain wall of the Cordilleras was also destroyed (Fig. 3). Due to the large north-south extension of the Andes, the differences are further intensified. What is common to the plateaus and long valleys, which are mainly between 2000 and 4000 m above sea level, is that they are densely populated and of great agricultural importance.

In the low regions (up to approx. 2500 m) even bananas, figs, avocado, cinnamon apples, sugar cane, wine, tree tomatoes, peppers as well as vegetables and flowers are grown in greenhouses (e.g. roses for export to Europe) (Fig. 4 ). Coffee and cocoa are added at higher altitudes and in some areas coca bushes for the widespread coca tea, a natural medicine. At high altitudes, potatoes, cereals (mainly the main foodstuffs corn, wheat and barley) and legumes (peas and beans) are grown. In the highest areas only extensive pasture farming is possible (cattle, horses, sheep, goats, llamas, alpaca, vicuñas).

The most important plateau in the interior of the mountain is the Altiplano in Bolivia and southern Peru and northern Chile (Fig. 5). It is approx. 1000 km long, approx. 300 km wide and is at an average height of well over 3000 m. Only a few mountains and ridges interrupt the flatness of the huge plateau. In the Altiplano, at 3812 m above sea level, Lake Titicaca with a length of 180 km and an area of 8,600 km² is the highest and largest navigable lake in the world. La Paz, the tallest city in the world, is located on the Altiplano at an altitude of 3600 to 3750 m.

The Altiplano has a large population density. The indigenous people (indigenous) are largely still extensive agriculture. Maize (up to 3850 m high), potatoes, oca (earth fruit), quinoa (millet-like highland cereals of the Inca) and barley are grown. The potatoes are kept for several years according to traditional Inca methods as a reserve. The high mountains of the Cordilleras border the Altiplano in the west and east. The forest border is located at about 4700 m and the snow line at about 6000 m above sea level.

The valley of the Rio Santa in northern Peru is given as an example of the long valleys. The Rio Santa rises at 4020 m below the Conocachapass and flows approx. 200 km to the north (Fig. 6). Then he turns west, breaks through the western Cordillera, here called the Black Cordillera, to irrigate an oasis in the Costa. The black cordillera (Cordillera negra; up to almost 5200 m) has low mountain ranges and was given this name because it does not carry snow. There, gold is mined in the opencast mine at an altitude of 4200 m. At such heights, the mining of precious metal ores is very common in Peru.

The White Cordillera runs parallel to the east(Cordillera Blanca; Image 7). It is covered with snow and heavily glaciated. The classic treasure of shapes of the ice age can be seen everywhere. The three-pointed Huascarán (6768 m, image 1), the highest mountain in Peru, protrudes from the chain of ice giants. The passes in the White Cordillera are between 4600 m and 4890 m high (Portachuelo de Llanganuco 4767 m, Punta Unión 4750 m).

Triggered by the May 31, 1970, earthquake at 3:23 p.m. (epicenter 50 km off the Pacific coast at a depth of 24 km), which lasted only 45 seconds but reached 7.7 degrees on the Richter scale Part of the north summit of the Huascarán (6665 m) on a length of 1200 m. Rock and ice crashed onto a glacier and finally sent a mudslide of 25 million m³ mass in a width of 1.5 km to the valley, which the city of Yungay completely buried (Fig. 8). The avalanche only took four minutes for its 16 km long run, reaching an hourly speed of 250 km. Only a few residents were able to save themselves; There were 20,000 deaths. In the main town of the Santa Valley, Huaraz(3090 m; 80,000 inhabitants), 30,000 people were killed by an avalanche caused by this earthquake. Huaraz was devastated by a debris and mudslide as early as 1941 and was hit by a powerful ice avalanche in 1958, so it had to be rebuilt several times.

The Santa Valley is only about 20 km wide and drops to 1200 m until the breakthrough in the Western Cordillera. It is densely populated. The population works in agriculture, which in some areas even reaches the heights of the Black Cordilleras. Potatoes, corn, wheat, barley, quinoa, etc. a. grown. Cattle are hardly kept, but numerous sheep and horses.

” Avenue of the volcanoes ” is often called the large longitudinal valley in Ecuador (approx. 300 km long and up to 20 km wide; several times interrupted by passes), which extends from the western and eastern cordillera from Tulcán in the north to around Riobamba in the South runs. The name goes back to ALEXANDER VON HUMBOLDT, who worked here in 1802 during his five-year long American research trip. HUMBOLDT was so fascinated by the mighty volcanoes that are set up on both Cordilleras in this part of the Andes that he tried to climb several volcanoes without having any mountaineering equipment, or one that was already known.

On the western cordillera are the volcanoes Imbabura (4550 m, image 9), Cotacachi (4939 m), Pichincha (4784 m), Atacazo (4463 m), Corazón (4788 m), Iliniza (5248 m) and the highest mountain in Ecuador, the Chimborazo with 6310 m. The Eastern Cordilleras are the volcanoes Cayambe (5790 m), Antizana (5758 m), Sincholagua (4893 m), Cotopaxi (5897 m, highest active volcano in the world), Quilindaña (5023 m), Tungurahua (5023 m) and altar (5320 m) on. In between there are also largely eroded volcanoes with large collapse funnels (caldera ; Fig. 10).

The Pichincha was last active for weeks in October 1999. He poured 5500 tons of ashes into the city at his feet, the Ecuadorian capital Quito, within 24 hours. Fortunately, there were only four injuries while removing the ash load from a roof.

The Cotopaxi is believed to be the highest active volcano on earth. It was climbed for the first time on November 28, 1872 by the German geologist WILHELM REIß. WHYMPER spent one night on the summit in 1880. The largest volcanic eruptions to date occurred in 1877. Four powerful eruptions, the lava of which reached the valley 35 km away within an hour. At a height of 4800 m there is a hut (Refugio Jose T. Rivas) that is the starting point for ascents (Fig. 11).

The Tungurahua, whose name means “little hell” in Quechua, had a month-long eruption period in the middle of 2000. The eruptions melted parts of the glacier at the summit. This triggered a mudslide that spilled a part of Baños 100 m wide and 4 m high; The avalanche also interrupted the thoroughfare from the Andes to the Amazon region (Fig. 12). The fiery slag ejection and gas explosions were spookily observed at night. Already at the end of 2001 there were new volcanic eruptions on the Tungurahua.

HUMBOLDT at Chimborazo

AV HUMBOLDT has carried out studies with partial ascents on the Pichincha, Antizana, Cotopaxi and Altar volcanoes.

On June 23, 1802, he attempted to climb the Chimborazo volcano. This mountain, with its five peaks, was considered the highest mountain in the world at the time because it is farthest from the center of the earth due to the bulging of the globe at the equator. HUMBOLDT, then 32 years old, came up to 5920 m. Then a column 20 m wide and 175 m deep prevented any further progress.

His diary later read:

“We wore short boots, simple clothes, no gloves, they are hardly known here. We were suffering from shortness of breath and the nausea aggravated us even worse. We also bleed from the gums, from the lips, the white of our eyeballs was bloodshot. We felt head weakness, a constant dizziness, which is very dangerous in our situation ”.

Even though the height reached was later corrected to 5759 m due to the inaccurate boiling thermometer at such heights, HUMBOLDT was the first white man to reach such a height. An obelisk at the first hut (Refugio Hermanos Carrel) at 4800 m reminds us of this today. There is a sign there that HUMBOLDT thanks for its geo-ecological achievements. But HUMBOLDT is already highly valued everywhere in South America.

The first ascent of the Chimborazo was carried out almost 80 years later, on January 4, 1880, by the Englishman EDWARD WHYMPER, who is also the first climber of the Matterhorn and numerous other highest peaks (in Ecuador including Cayambe and Antizana). He was accompanied by the mountain guides JEAN-ANTOINE and LOUIS CARREL. The latter was still his competitor on the Matterhorn. Your route is today’s normal route. The second, upper hut on the mountain at a height of 5000 m was named after the first climber. Refugio Edward Whymper is the highest, year-round hut in the world.