The 18th century explorer Alexander von Humboldt called Cotopaxi “the most beautiful and perfect volcano” in the world, and so it is. Its glacier-covered cone rises above the high Andean plateau to 5897m, the second-highest peak in Ecuador. It has erupted periodically throughout recorded history, repeatedly damaging nearby cities like Latacunga, which has been rebuilt at least twice. The eruptions send hot clouds of ash and steam down its valleys: these have sometimes reached the outskirts of Quito and even entered our own Rio Pastaza.
There were major eruptions in the 1740s, 1768, 1853, 1877, 1880, and 1903-4 (and much larger ones in the geologically recent past). Edward Whymper, British mountaineer who climbed Cotopaxi and then made the first ascent of the even-taller Chimborazo in 1880, had the incredible luck of witnessing Cotopaxi explode while he was near Chimborazo’s summit (luckily this happened after he had gotten off Cotopaxi!):
“On July 3, 1880, I was engaged in an ascent of Chimborazo, and was encamped on its western side at 15,800 feet above the sea. The morning was fine…we saw to our north the great peak of Illiniza and 20 miles to its east the great peak of Cotopaxi, both without a cloud around them, and the latter without any smoke issuing from its crater – a most unusual circumstance; indeed, this was the only occasion on which we noticed the crater free from smoke during the whole of our stay in Ecuador. …At 5:45 A.M. a column of smoke of inky blackness began to rise from the crater. It went straight in the air, rapidly curling, with prodigious velocity, and in less than a minute had risen 20,000 feet above the rim of the crater. …”
“We knew that we saw from our station the upper 10,000 feet of the volcano, and I estimated the height of the column of smoke at double the height of the portion seen of the mountain. The top of the column was therefore nearly 40,000 feet above the sea. At that elevation it encountered a powerful wind blowing from the east, and was rapidly borne for 20 miles toward the Pacific, seeming to spread very slightly and remaining of inky blackness, presenting the appearance of a gigantic inverted L, drawn upon an otherwise perfectly clear sky. It was then caught by a wind blowing from the north, and was borne toward us, and appeared to spread rapidly in all directions. As this cloud came nearer and nearer, so, of course, it seemed to rise higher and higher in the sky, although it was actually descending. Several hours passed before the ash commenced to intervene between the sun and ourselfes, and when it did so we witnessed effects which simply amazed us. We saw a green sun, and such a green as we have never, either before or since, seen in the heavens. We saw patches or smears of something like verdigris green in the sky; and they changed to equally extreme blood-reds, or to coarse brick-dust reds, and they in an instant passed to the color of tarnished copper or shining brass. Had we not known that these effects were due to the passage of the ash, we might well have been filled with dread instead of amazement; for no words can convey the faintest idea of the impressive appearance of these strange colors in the sky, seen one minute and gone the next, resembling nothing to which they can be properly compared, and surpassing in vivid intensity the wildest effects of the most gorgeous sunsets.”
“The ash commenced to pass overhead at about mid-day. It had travelled (including its detour to the west) eighty-five miles in a little more than six hours. At 1.30 it commenced to fall on the summit of Chimborazo, and, before we began to descend, it caused the snowy summit to look like a ploughed field. The ash was extraordinarily fine, as you will perceive by the sample I send you. It filled our eyes and nostrils, rendered eating and drinking impossible, and reduced us to breathing through handkerchiefs. It penetrated everywhere, got into the working-parts of instruments and into locked boxes. The barometer employed on the summit was coated with it, and so remains until this day. That which ssed beyond Us must have been finer still. It travelled far to our south, and also fell heavily upon ships on the Pacific. I find that the finer particles do not weigh the twenty-five thousandth part of a grain, and the finest atoms are lighter still. By the time we returned to our encampment, the grosser particles had fallen below our level, and were settling down into the valley of the Chimbo, the bottom of which was 7,000 feet beneath us, causing it to appear as if filled with thick smoke. The finer ones were still floating in the air, like a light fog, and so continued until night closed in.”
“In conclusion, I would say that the terms which I have employed to designate the colors which were seen are both inadequate and inexact. The most striking features of the colors which were displayed were their extraordinary strength, their extreme coarseness, and their dissimilarity from any tints or tones ever seen in the sky, even during sunrises and sunsets of exceptional brilliancy. They were unlike colors for which there are recognized terms. They commenced to be seen when the ash began to pass between the sun and ourselves, and were not seen previously. The changes from one hue to another, to which I have alluded, had obvious connection with the varying densities of the clouds of ash that passed; which, when they approached us, spread irregularly, and were sometimes thick and sometimes light. No colors were seen after the clouds of ash passed over-head and surrounded us on all sides.”
“I photographed my party on the summit of Chimborazo whilst the ash was commencing to fall, blackening the snow-furrows; and, although the negative is as bad as might be expected, it forms an interesting souvenir of a remarkable occasion. ” (Whymper, E. 1884. Coloured sky observed during eruption of Cotopaxi. Nature, 29: 199-200.) Whymper estimated that over 2 million tons of debris were ejected during this eruption.
It had been silent for 70 years, and I did not think I would see an eruption in my lifetime. But yesterday and the day before, it came back to life. The explosions so far are regarded, even though the ash cloud rose many kilometers into the sky. A massive eruption may be on its way, and this would be devastating for the cities around Cotopaxi, though it might give us the chance to see Whymper’s extraordinary sky colors for ourselves.