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The last significant eruption of Cotopaxi volcano was in 1907 and produced ash explosions and small pyroclastic flows but no lava flows.
1905 and 1906 eruptions
The eruptions in 1905 and August 1906 consisted in small ash explosions.
A medium-sized eruption (VEI 3) started on 26 Sep 1903 and lasted until December 1904. The eruption occurred from the central vent and produced tall ash plumes, pyroclastic flows and lahars. During explosions on or around 23 October, lightnings were noted by observers, the Times reports the next day: "Since Thursday, electric discharges have been notices on the eastern side of the Andes. Rumblings were heard near the towns this morning, and ashes fell for three-quarters of an hour." (The Times, 25 Oct 1903, "COTOPAXI IN ERUPTION")
1880 vulcanian eruption
One of the largest eruptions of Cotopaxi in historic times began on 3 July 1880. A powerful explosion sent an ash column of 20,000 ft (ca. 6 km) height above the crater in less than a minute.
The British explorer Edward Whymper was climbing Chimborazo at the time of the eruption and reported extremely vivid and strange light and color effects when the large ash plume drifted over him: "... several hours passed before the ash commenced to intervene between the sun and ourselves; and, when it did so, we witnessed effects which simply amazed us. We saw a green sun..." (click to read more)
[hide] from Whymper, E, 1884, Coloured sky observed during eruption of Cotopaxi, in Nature, vol 29
pp199-200, London, Macmillan:
"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 borner for 20 miles toward the Pacific, seeming to spread veryl 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 directons. 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, andwhen 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 pataches 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 tarnjished copper or shining brass.. Had we not known that these effectes were due to the passage of the ash we might well have been filled with dread instead of amazement; for no words can convery 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."
1877 vulcanian eruption
4 large eruptions occurred at Cotopaxi between January and September 1877. The explosions produced high eruption columns, heavy ash fall, pyroclastic flows and lahars. The eruption caused much damage and there were fatalities.
A 3 day long eruption occurred at Cotopaxi from 13-15 September 1853 and produced ashfall, pyroclastic flows and small lahars.
1768 vulcanian-subplinian eruption
One of the largest historical eruptions of Cotopaxi occurred on 4 April 1768. A large vulcanian explosion took place (VEI 4) and generated a high ash plume, heavy ash fall and pyroclastic flows. Large bombs were falling at great distances. The eruption caused fatalities and extensive damage.
[hide] "Bombs fell as far as La Cienega (22 km SW from the crater) and Tanicuchi (24 km SW from the crater)" (Pistolesi et al, 2011).
Note: the "bombs" described refer only to the large size (>64 mm diameter) of tephra fragments deposited as fall-out from the eruption column. They are not classic ballistic ejecta (it is physically impossible to eject bombs that far on a ballistic trajectory).
- Barberi et al (1995) "Chronology and dispersal characteristics of recently (last 5000 years) erupted tephra of Cotopaxi (Ecuador): implications for long-term eruptive forecasting", Journal of Volcanology and Geothermal Research, v 69 (3-4), pp. 217-239
- Pistolesi et al (2011) "Physical volcanology of the post–twelfth-century activity at Cotopaxi volcano, Ecuador: Behavior of an andesitic central volcano", GSA Bulletin; May 2011; v. 123; no. 5-6; p. 1193-1215
Several small to medium-sized explosions occurred in 1866. Lahars and floods damaged the town of Latacunga and the fallout of coarse pumice west of the volcano destroyed several farms.
A major explosive eruption started in May 1744 at Cotopaxi volcano. It produced extensive ash fall 7-10 cm thick 10 km west of the crater.
2 larger explosive eruptions occurred in December 1742, producing ashfall, pyroclastic flows, and destructive lahars. The eruption caused fatalities.
In 1534 the conquistadors were at war with the locals for control over Ecuador. It is reported that during a battle on the flanks of Cotopaxi, the volcano started an eruption and filled the air with "hot ash" (pyroclastic surges?). The locals viewed the event as a divine sign from their god fled in fear. The Spanish who had no experience with volcanic activity were terrorized and did the same.
A lahar from the 1534 eruption destroyed La Contiega village.
The Chillos Valley Lahar 4500 years ago
The Chillos Valley Lahar from Cotopaxi volcano's north and NE slopes is the largest known debris flow in the northern Andes during the Holocene (11,700 years ago to present).
It descended river systems and flowed 326 km north–northwest to the Pacific Ocean and more than 130 km east into the Amazon basin. The massive avalanche occurred around 4500 years ago.
Minard Hall and Patricia Mothes (2008) "The rhyolitic–andesitic eruptive history of Cotopaxi volcano, Ecuador", Bull. Volc., v. 70 (6), pp. 675-70
Jan Kozák and Vladimír Čermák (2010) "The Illustrated History of Natural Disasters", Springer (Netherlands), pp 95-96
Barberi et al (1995) "Chronology and dispersal characteristics of recently (last 5000 years) erupted tephra of Cotopaxi (Ecuador): implications for long-term eruptive forecasting", Journal of Volcanology and Geothermal Research, v 69 (3-4), pp. 217-239
Pistolesi et al (2011) "Physical volcanology of the post–twelfth-century activity at Cotopaxi volcano, Ecuador: Behavior of an andesitic central volcano", GSA Bulletin; May 2011; v. 123; no. 5-6; p. 1193-1215
Mothes et al (1998) "The enormous Chillos Valley Lahar: an ash-flow-generated debris flow from Cotopaxi Volcano, Ecuador", Bull. Volc., v. 59 (4), pp. 233-244
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