Natural paradises in danger to be saved: Andes



by LORENZO CIOTTI

Natural paradises in danger to be saved: Andes

The extreme climate in the Andes is already contributing to the melting of glaciers and the migration of both highland populations and the animals themselves. With its 7200 km in length (from the Isthmus of Panama in the north to Cape Horn in the south) it is traditionally considered the longest mountain range in the world, representing the ideal continuation towards the south of the mountain ranges of North America, western and central.

Its average width is 240 km, reaching 500 km at its widest point (between the 18th and 20th parallel south); the average height is about 4000 m. The Andes extend to Tierra del Fuego and, plunging into the sea, the highest peaks form islands such as South Georgia and the South Sandwich Islands, the South Orkney Islands and the South Shetland Islands.

They re-emerge in Antarctica. The climate in the Andes varies considerably according to latitude, altitude and therefore proximity to the sea. The southern sector is cold, intensely snowy even at relatively low altitudes and rainy, while the central one is drier and milder.

The northern sector of the Andes is generally rainy, and relatively hot, with an average temperature of 18 ° C, in Colombia. The climate is characterized by changes in heat. The origin of the Andean chain can be traced back to the dynamics of the terrestrial plates or to the tectonics of the plates.

The collision between two portions of the crust, in particular the oceanic plate known as the Nazca plate (composed of oceanic crust) with the South American plate (formed by continental crust) is the cause of the orogeny of the Andes chain.

The Andes of Chile and Argentina can be divided into two climatic and glacological zones; the dry Andes and the humid Andes. The dry Andes extend from the latitude of the Atacama Desert to the area of ​​the Maule River; rainfall is more sporadic and strong fluctuations in temperatures occur.

The equilibrium line undergoes drastic shifts over short periods of time, leaving the glaciers ablating or accumulating. Between 100 and 60 million years ago there was a shift of the lithosphere in subduction towards the east causing the formation of the second volcano arc, which explains the birth of the western mountain range.

In the meantime, the strait between the two mountain ranges began to fill with sediments deriving from the erosion of the ocean on the crust, thus allowing the formation of the Andean plateau to begin. Finally, between 15 and 2 million years ago the stratovolcanoes were formed, steep cone volcanoes in which the eruptions are characterized by alternating lava flows with ashes and lapilli (typical Vulcanian eruptions).