Moi, Paul Derand

Moi, Paul Derand

Guatemala's most dangerous volcanoes

These are all Guatemala volcanoes that have erupted in the last 500 years, that have a Volcanic Activity Index (VAI) of at least 0, and that have the potenital to threaten several thousands of people or more in an eruption. 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.

 

Tacana (dangerosity 1,6):

Tacana is a sub-plinian (VEImax=4) stratovolcano located in the border between Guatemala and Mexico.

It has a crater lake and mild phreatic eruptions took place in historical times.

Its most powerful known explosive activity occurred at about 70 AD (± 100 years), it had a VEI of 4 and produced pyroclastic flows.

The agricultural valley at its NNE foothills is covered with thick deposits of lahars. From its headwaters in Guatemala, the valley (Rio Coatan) drains through Mexico to the Pacific Ocean. In case of a péléan eruption with associated lahars, the volcano could threaten more than 250K people.

Luckily, the volcano's VAI is only 0,65 (little).

 

Santa Maria (dangerosity 4,9):

Santa Maria is a plinian (VEImax=5,74) volcano located in northeastern Guatemala. Since the 1902 eruption, the eruptions come from the Santiaguito dome complex located in a caldera that is breached to the Southeast, so that the city of Quetzaltenango is protected from pyroclastic flows and lahars (but  not from ashfall). However, places located on the Pacific foodplain to the South of the volcano (interior Retalhuleu department) are frequently affected by lahars from Santiaguito during the rainy season due to heavy rainfall on loose volcanic deposits. Moreover, fast-moving pyroclastic flows can occur, and these may travel several kilometres from the dome, and these could affect villages to the immediate South or Southeast of the volcano, such as San Marcos. Ashfall can also be important: in the 1902 eruption ashfall was felt as far as 4000 km, in a vulcanian eruption, moderate ashfall can be felt in a 20 km radius, enough to affect Quetzaltenango (located 10 km to the Northeast).

See here the risk map for places located to the South of the volcano.

Santa Maria has frequent and strong eruptions, this is why it has a VAI of 2,43 (high).

 

Almolonga (dangerosity 0,6):

Almolonga is a caldera located immediately South of Quetzaltenango, Guatemela's second largest city. Its historical eruptions all came from a lava dome complex, Cerro Quemado.

It largest eruption around 800CE was vulcanian (VEImax=3) and consisted of the collapse of Cerro Quemado lava dome. This produced a lateral blast and a debris avalanch that reached the Sete Orejas Mountain, located 6 km to the West.

Since that time, the lava dome has re-constructed, waiting for another strong eruption to make it collapse again.

If Cerro Quemado lava dome was to happen again, the city of Quetzaltenango, located only 4 km away, would be destroyed. The problem is that this city has a population of 661K inhabitants...

Luckily, its eruptions are infrequent and it has a VAI of only 0,2.

 

Fuego:

Fuego is one of the most active volcanoes in Guatemala. It is located in southcentral Guatemala. It has a VAI of 2,05 (high) as its eruptions are frequent and mild to moderate: Frequent vigorous historical eruptions have been recorded at Fuego since the onset of the Spanish era in 1524, and have produced major ashfalls, along with occasional pyroclastic flows and lava flows.

The volcano is sub-plian (VEImax=4). If a subplinian eruption occured, there would be light (millimetric accumulations) ashfall in a 450 km radius, entire Guatemala would be affected by light ashfall! Moderate (centimetric to decimetric accumulations) ashfall would occur in a 45 km radius, paralysing the capital city. Pyroclastic flows could measure up to 7 km long like in 1974, threatening more than a thousand people. Eruptions of this intensity have occured 7 times since the spanish conquest, and the last one was in 1974.

Vulcanian eruptions can also generate large ashfall. There could be light ashfall as far as 200 km and moderate ashfall as far as 20 km. Light ashfall could occur in the southern half of Guatemala and moderate ashfall could be felt as far as Antigua, Escuintla and Santa Lucia Cotzumalguapa. Pyroclastic flows from a vulcanian eruption would be luckily too small (5km) to threaten anybody.

Strombolian activity would only be the cause light ashfall 10 to 50 km from the volcano or generate small pyroclastic flows mainly by the collapse of lava flow fronts.

Lava flows may also happen during eruptions, but even though they entually reach the lower flanks, they would not threaten settlements.

See the risk map for this volcano.

 

Acatenango (dangerosity 2,0):

Acatenango is a vulcanian (VEImax=3) volcano located in southcentral Guatemala. It has a VAI of 1,08 (moderate to low) because its eruption are rather infrequent and mild.

In the case of a vulcanian eruption there would be pyroclastic flows 8,5 km long, affecting Yepocapa, Acatenango, San Antonio Najapa, Aldea la Soledad, San Jose Calderas, San Miguel Duenas and Alotenango, that have a total population of 76K people. Light ashfall could be felt as far as 200 km from the volcano (affecting the southern half of Guatemala), and moderate ashfall could occur as far as 20 km from the volcano (as far a Antigua and Chimaltenango).

Andesitic lava flows from this volcano could travel up to 4 km and reach a minimum altitude of 2100m.



24/02/2015
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