Moi, Paul Derand

Moi, Paul Derand

Ecuador's most dangerous volcanoes

These are all Ecuador volcanoes that have erupted in the last 500 years, that have a Volcanic Activity Index (VAI) of at least 1 and that have the potential to threaten more than 10,000 people if their largest possible eruption occurs. They are classified by their dangerosity (depending of the VAI and the number of people eventually threatened): class 0 is very little to little, class 1 is a little to moderate, class 2 is dangerous to very dangerous, class 3 is very dangerous, class 4 is extremely dangerous. Values superior to 4 can be used if necessary.

 

Tungurahua (class 2.9):

Tungurahua is a glacier capped plinian (VEImax=5) volcano located in central Ecuador.

If its largest possible eruption was to occur, moderate ashfall would occur 160 km to the Northwest and 40 km to the Southeast, lahars would flow 15 km in the ravines on all flanks), pyroclastic flows and andesitic to dacitic lava flows could flow on the volcanos's steep sides as far as 15 km from the summit crater. In case of a large eruption of that size, the town of Banos (15K inhabitants), which is located 10 km from the volcano, may be affected by pyroclastic flows, ashfall, lahars and lava flows.

In case of a vulcanian or a sub-plinian (VEI of 3 or 4) eruption, Banos will be affected as well, with pyroclastic flows, lava flows, lahars and ashfall.

Moreover, edifice collapse has occured twice in this volcano's history. As the volcano is quite steep-sided, it is possible again.

This volcano has a VAI of 2,47, which is high.

 

Cotopaxi (class 3.7):

Cotopaxi is a glacier capped plinian (VEImax=5) volcano located in central Ecuador, 50 to 60 km to the South of Quito.

If its largest possible eruption was to occur, there would be moderate ashfall as far as 240 km to the Northwest and 60 km to the Southeast, lahars  flowing down all flanks 25 km from the crater, measuring as long as 200 km into rio Guayllabamba, rio Napo and rio Culapachan and pyroclastic flows and andesitic lava flows as long as 12,5 km, reaching the lower flanks. In the case of a plinian (VEImax=5) eruption, Latacunga, Sangolqui, Cumbaya, Tanucuchi, Saquisili, Salcedo may all be affected by both lahars and ashfall. The total affected population would be 245K people.

In 1877, a sub-plinian (VEI=4) eruption occured. Pyroclastic flows descended all sides of the volcano and lahars travelled more than 100 km into the Pacific Ocean and Western Amazon basin. The town of Lacatunga was partially destroyed and there were thousands of victims. This sort of eruption can also generate moderate ashfall as far as 120 km to the Northwest and 30 km to the Southeast. In case a new similar eruption occurs, "only" Lacatunga, Sangolqui, Tanucuchi and Saquisili will be affected by both lahars and ashfall, this makes a total of 120K people.

In case of a vulcanian (VEI=3) eruption, pyroclastic flows and lava flows would only flow on the western flank of the volcano because the summit crater is breach to the W. In this way, if most of the tehpra deposits and metlted ice (melted because of heat) are on the western slope, lahars would flow only into rio Culapachan, for  up to 50 km. "Only" Lacatunga (57K people) would be affected by both ashfall and lahars.

This volcano has a VAI of 1,53, which is moderate.

 

Guagua Pichincha (class 2.7:

Guagua Pichincha is a plinian (VEImax=5) volcano located in North-central Ecuador, 10 to 15 km to the West of Quito. It has a caldera that is breached to the SW.

In the case of the largest possible eruption possible (VEImax=5), moderate ashfall would occur up to 760 km to the Northwest and 190 km to the Southeast and heavy ashfall would occur up to 76 km to the Northwest and 19 km to the Southeast. Lahars would flow as far as 26 km to the South East (where the caldera is breached) and 14 km outside the caldera. In this case, Lloa, the western part of Quito (Chillogallo, centro Historico, La Libertad, Chilibulo, Magdalena, San Bartolo, Solanda and La Mena) and Mindo would be affected by lahars and heavy ashfall. A total of 162K people would be threatened by an eruption of that size.

However, if a subplinian (VEI=4) eruption occurs like in 1660, the caldera's walls will protect Quito from lahars. However, the danger of ashfall remains important: in 1660, there was ashfall in a 1000 km radius, and the accumulation of ash in Quito was 30 cm! Mindo, however, will be affected by lahars because it is in front of the caldera's breach. So only Mindo, a town of 3K inhabitants, would be affected by both moderate ashfall and lahars. And the provinces of Pichincha, Santo Domingo, Cotopaxi and Imbadura would be affected by moderate ashfall.

In case of a vulcanian eruption (VEI=3), only moderate ashfall poses a problem, only 50 km around the volcano, so only in the Pichincha province.

This volcano has a VAI of 1,23, which is moderate.



11/02/2015
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