Guatemala : volcanoes

Here is some information about 5 of the most interesting volcanoes of Guatemala.

Volcano Pacaya

Pacaya is an active complex volcano in Guatemala, which first erupted approximately 23,000 years ago, and has erupted at least 23 times since the Spanish conquest of Guatemala. After being dormant for a century, it erupted violently in 1965, and has been erupting continuously since then. Much of its activity is Strombolian, but occasional Plinian eruptions also occur, sometimes showering the nearby city of Antigua with ash. It lies approximately 25 to 30 km south of Guatemala City.

It is easily accessible from Antigua Guatemala and Guatemala City, and so is a popular tourist attraction

Geological history

Pacaya is part of a chain of volcanoes stretching along the Pacific coast of Guatemala, formed by the subduction of the Cocos Plate underneath the Caribbean Plate. It lies on the southern edge of a sizable caldera formed in the Pleistocene age which contains Lago de Amatitlán. The caldera has been the source of at least nine very large explosions over the last 300,000 years, erupting a total of about 70 km³ of magma.
Since the last caldera-forming eruption 23,000 years ago, several smaller vents within and around the caldera have seen eruptive activity. Pacaya is the largest post-caldera volcano, and has been one of Central America's most active volcanoes over the last 500 years. It has erupted at least 23 times since the Spanish conquest.
About 1100 years ago, the volcano's edifice collapsed, causing a huge landslide. Deposits from the landslide travelled about 25 km from the volcano down to the Pacific coastal plain. The landslide left a large crater, within which the current active cone has grown.

The presence of a magma chamber at shallow depths beneath Pacaya means that distortion of the cone leading to instability and future landslides remains a hazard to the surrounding areas.

Recent eruptions

Between 1860 and 1961, the volcano was dormant, but re-awoke in 1961 with an effusive eruption of lava from its southern flank. Since 1965, eruptions have been virtually continuous. They have mostly consisted of Strombolian eruptions, with hundreds of small explosions occurring every day. Occasionally, larger eruptions have occurred, sometimes showering nearby towns and cities with volcanic ash. One explosive eruption in 2000 briefly forced the closure of Guatemala City's La Aurora International Airport.

Tourism

With its almost continuous activity and proximity to both Guatemala City and Antigua Guatemala, the volcano has been a popular location for tourism. The volcano and surrounding area now lie within Pacaya National Park, created to manage tourism in the area and generate income from tour groups, who are charged a small fee to enter the park.

During 2006, a slight increase in Pacaya's volcanic activity allowed for the creation of several lava rivers that slowly flowed down its slope.

Volcano Fuego

Volcán de Fuego ("Volcano of Fire") is an active stratovolcano in Guatemala. It is close to the city of Antigua Guatemala. It has erupted frequently since the Spanish conquest. "Fuego" is famous for being almost constantly active at a low level. Smoke issues from its top daily, but larger eruptions are rare. The last eruption occurred in 2006[1]. The volcano is joined with Acatenango and collectively the complex is known as La Horqueta.

It is accessible from Antigua Guatemala.

Volcano Acatenango

Acatenango is a stratovolcano in Guatemala, close to the city of Antigua. The volcano has two peaks, Pico Mayor (Highest Peak) and Yepocapa (3,880 m) which is also known as Tres Hermanas (Three Sisters). Acatenango is joined with Volcán de Fuego and collectively the volcano complex is known as La Horqueta.

The Fuego-Acatenango massif comprises a string of five or more volcanic vents along a north-south trend that is perpendicular to that of the Central American arc in Guatemala. From north to south known centers of volcanism are Ancient Acatenango, Yepocapa, Pico Mayor de Acatenango, Meseta, and Fuego. Volcanism along the trend stretches back more than 200,000 years. Although many of the centers have been active contemporaneously, there is a general sequence of younger volcanism, from north to south along the trend.

This massive volcano complex towers more than 3,500 metres above the Pacific coastal plain to the south and 2,000 metres above the Guatemalan Highlands to the north. The volcano complex comprises remnants of multiple eruptive centers, which periodically have collapsed to form huge debris avalanches. The largest of these avalanches extended more than 50 kilometres from its source and covered more than 300 square kilometres. The volcano has potential to produce huge debris avalanches that could inundate large areas of the Pacific coastal plain. In areas around the volcanoes and downslope toward the coastal plain, more than 100,000 people are potentially at risk from these and other flowage phenomena.

The only known historical eruptions of Acatenango volcano occurred in the 20th century, between 1924 and 1927 from just north of the summit peak (Pico Mayor) and again in December 1972 from the saddle between Yepocapa and Pico Mayor. These phreatic explosions generated ballistic volcanic bombs that fell near the summit craters and fine volcanic ash that fell up to 25 km away. In prehistoric time, Acatenango has erupted explosively to form widespread fall deposits, hot pyroclastic flows and lava flows. There have been numerous eruptions during the past 80,000 years from vents along the massif. The most recent explosive eruptions of Acatenango occurred 1,900 years ago (Pico Mayor), 2,300 years ago (Pico Mayor) and about 5,000 years ago (Yepocapa). If such eruptions were to recur, many people and costly infrastructure would be at risk.

It is accessible from Antigua Guatemala.

Volcano Santa Maria

Volcán Santa María is a large active volcano in the Western Highlands of Guatemala, close to the city of Quetzaltenango. Its eruption in 1902 was one of the three largest eruptions of the 20th century, and the third large eruption of that one year, after Mount Pelée in Martinique and Soufrière in St. Vincent. It was also one of the five biggest eruptions of the past 200 (and probably 300) years.

The 1902 eruption blasted away most of one side of the 3,772 m tall mountain. Some 5.5 cubic km (1.3 cubic miles) of volcanic material was ejected during the 19-day eruption, and the ash column reached heights of up to 28 km. The eruption devastated the surrounding areas.

In 1922, a new volcanic vent formed in the enormous crater, and formed a new volcano, named Santiaguito. Santiaguito has been erupting ever since and now forms a cone a few hundred metres tall, reaching an elevation of about 2,500 m. Today, it is possible to climb to the top of Santa María and look down on the ongoing eruptions at Santiaguito, 1,200m below, a situation which may be unique in the world.

It is accessible from Quetzaltenango.

Geological history

Steam rises from Santiaguito. The area of the flank destroyed by the 1902 eruption can be clearly seen. Lahar deposits snake down river valleys to the left of the image
Santa María is part of the Sierra Madre range of volcanoes, which extends along the western edge of Guatemala, separated from the Pacific Ocean by a broad plain. The volcanoes are formed by the subduction of the Cocos Plate under the Caribbean Plate.
Eruptions at Santa María are estimated to have begun about 30,000 years ago. For several thousand years, eruptions seem to have been small and frequent, building up the large cone of the volcano, reaching about 1,400 m above the plain on which the nearby city of Quetzaltenango sits. Following the cone-building eruptions, activity seems to have changed to a pattern of long periods of repose followed by the emission of small lava flows from vents on the flanks.

The cone built by the eruptions had a volume of about 10 km³, and consisted of a mixture of basalt and andesite lavas.

1902 eruption

The first eruption of Santa María in recorded history occurred in October 1902. Before 1902 the volcano had been dormant for at least 500 years and possibly several thousand years, but its awakening was clearly indicated by a seismic swarm in the region starting in January 1902. The eruption began on 24 October, and the largest explosions occurred over the following two days, ejecting an estimated 5.5 km³ of magma. The eruption was one of the largest of the 20th century, comparable in magnitude to that of Mount Pinatubo in 1991.

The pumice formed in the climactic eruption fell over an area of about 273,000 km², and volcanic ash was detected as far away as San Francisco, 4,000 km away. The eruption tore away much of the south-western flank of the volcano, leaving a crater about 1 km in diameter and about 300 m deep, stretching from just below the summit to an elevation of about 2,300 m.

Because of the lack of previous activity at Santa María, local people did not recognise the preceding seismicity as warning signs of an eruption. At least 5,000 people died as a result of the eruption.

Volcano Santiaguito

The 1902 eruption was followed by 20 years of dormancy. In 1922, new eruptions began, with the extrusion of a lava dome in the crater left by the 1902 eruption. The dome was christened Santiaguito, and since then, activity has been virtually constant. Santiaguito now reaches a height of about 2,500 m, and has a volume of about 1 km³. From the summit of Santa María, it is possible to look down on the eruptions at Santiaguito a mile below.

Dome growth at Santiaguito has alternated between growth caused by the emission of lava flows, and inflation caused by the injection of magma into the middle of the dome. These dome growth types are described by volcanologists as exogenous and endogenous respectively. Activity has been concentrated at several different vents, and Santiaguito now has the appearance of several overlapping domes.

Although most of Santiaguito's eruptive activity has been relatively gentle, occasional larger explosions have occurred.

In 1929, part of the dome collapsed, generating pyroclastic flows which killed anywhere from several hundred up to 5,000 people.

Occasional rockfalls have generated smaller pyroclastic flows, and vertical eruptions of ash to heights of a few kilometres above the dome are common.

Volcanic hazards at Santa María and Santiaguito

The areas to the south of Santa María are considerably affected by volcanic activity at Santiaguito. Currently, the most common volcanic hazard at Santa María is lahars, which frequently occur in the rainy season due to heavy rainfall on loose volcanic deposits. The town of El Palmar, 10 km from Santiaguito, has been destroyed twice by lahars from Santiaguito, and infrastructure such as roads and bridges have been repeatedly damaged. Lahar deposits from Santiaguito have affected rivers all the way downstream to the Pacific Ocean.

Lava flows do not occur frequently from Santiaguito, and tend not to stretch more than a few kilometres from the dome. The magma at Santiaguito is rich in silica and is thus highly viscous. Flows are therefore very slow-moving and are of little danger to human life, although property damage may occur. Fast-moving pyroclastic flows can occur, and these may travel several kilometres from the dome.

One hazard which could be devastating is the collapse of Santa María itself. The 1902 crater has left the southern flank of the mountain above Santiaguito highly over-steepened, and a large earthquake or eruption from Santiaguito could trigger a huge landslide, which might cover up to 100 km². However, this is thought to be unlikely in the short term.

In light of the threat it poses to nearby populations, Santa María has been designated a Decade Volcano, identifying it as a target for particular study by volcanologists to mitigate any future natural disasters at the volcano.