The Ecuadorian Andes run in two massive parallel mountain ranges down the heart of the country.  In between these two cordilleras, lies relatively lower, hilly and very fertile land, where the majority of the highland dwellers live.  The Cordillera Occidental cradles the western side of these heavily populated Inter-Andean valleys, while the Cordillera Oriental cradles the eastern side.  In the northern Ecuadorian Andes there are ten snowcapped volcanoes that soar over 5000 meters (16,403 feet) above sea level.  Each volcano stands sentinel over its own domain, making each mountain particularly magnificent.  In the southern Andes the volcanoes are much older and often crumbling, resulting in lower and relatively less impressive mountains, but deep and steep gorges and valleys.

The outer flanks of the mountains hold a much more untamed area where an amazingly diverse amount of flora grow in the wild profusion of the cloud forests.  Known as ceja andina (eye brows of the Andes) to locals, these forests are eternally covered in mist that rises from the tropical lowlands where it condenses in the form of clouds near the icy mountain tops.

Geology

In this tectonic puzzle of the world’s surface, no piece ever fits together perfectly.  Two of these pieces in particular have affected the geography of  Ecuador and the South American continent the most:  the Nazca Plate, submerged below the Pacific Ocean moving slowly eastward pushing against the South American Plate which essentially is the continent of South America.  The denser and heavier Nazca Plate undercuts the lighter and more buoyant South American Plate.  Scientists refer to this as subduction, a slow but often violent collision of two tectonic plates that generates enough friction and heat to melt the edges of the plates together with the rocks and minerals they are composed of.  This is the origin of the enormous quantities of magma underneath the Andes, and the lava that is frequently thrown from the craters of the Andean volcanoes.  This process not only formed the Andes, but also diverted the Amazon River toward the Atlantic Ocean.  At one time the Amazon flowed into the Pacific, but finding its route blocked it eventually found its way to the Atlantic, bringing with it alluvial sediment from the Andes forming the Amazon Basin.
 

Basically, one could say that the Ecuadorian Andes are made of recycled marine earth.  Even though you probably would not find marine fossils in the high Ecuadorian Andes, you can understand the process by which these massive volcanoes took form and from where the material came.  In Ecuador, almost every mountain has volcanic origins, including the Galapagos Islands.  There are only four exceptions to this:  Saraurco, Cerro Hermoso in the Llaganantes, the mountain mass of Cúbillín and Quilimas, as well as the mountain mass of Achipungo and Soroche.  Every other mountain in Ecuador either will erupt, has erupted or is erupting.
 

The Ecuadorian Andes took form at least 26 million years ago. However, the events that have been most influential in the appearance and basic form of these impressive mountains happened as only 5 million years ago.  Of course, these events continue to modify the topography to today although the short human life span does not permit us to notice these changes.

It is not uncommon to see Ecuadorian volcanoes with its flanks scoured of all life by recent pyroclastic or lava flows, whose summits glow incandescent at night.  These eruptions are more often than not very explosive.  The lava is often highly viscous, therefore pressure inside the volcano builds up easily and rapidly.  An eruption can easily cover an entire side of a mountain in lava and ash, adding sometimes up to a meter to the elevation of an adjacent valley’s floor while destroying every living plant and animal in it and ruining its fertility for some years.  How many ancient Ecuadorians have been buried in these eruptions, covered underneath ash and lahars?
 

With or without eruptions, these volcanoes are not only beautiful, but dangerous.  Written testimonies of survivors of past eruptions attest to this.  While many live peacefully and tranquilly under the shadows of these stunning mountains, geologists can see the danger of not being aware of the mountains’ dangers.  According to these scientists, there are over 25 volcanoes in Ecuador that could erupt either at any time, or in the near future.  Several have shown their volatile character several times since the Spanish conquistadors first arrived in this country.

Cotopaxi first showed itself to the Spanish when it interrupted a battle between the Conquistadors and the Incas, sending both sides fleeing.  The Incas took the eruption as a bad omen and although frightened, the Spanish took advantage of the situation and pursued the fleeing Incas.  Later, Cotopaxi belched lava that caused lahars to sweep down its gorges, causing and destruction widespread panic.  In 1877, it also blew up ash that reached the Guayaquil- Panama shipping route in the Pacific Ocean; almost 300 km (186 miles) out to sea.  Not only did its ashes reach to sea, but its lahars tore through the upper Amazon, eventually reaching the Brazilian Atlantic and reached the mountains Pacific tributaries with great force.
 

Tungurahua awoke in 1918 briefly to take a light nap until erupting again in late 1999.  Guagua Pichincha, which had lain dormant since 1660 also awoke in 1999 along with Tungurahua to ring in the new century with fireworks of their own.  El Reventador awoke in 2002 to the surprise of the country after sleeping for 26 years.  It dropped ash over much of the country, closing many road and Quito's airport.  On the other hand, Sangay, since the beginning of written history never has slept.  Without fear of being wrong, one could say that the last eruption of this volcano was just yesterday.