Volcanic Hazards in Latin America: Nue
Ardentes & Lahars
Circum-Pacific Ring of Fire
This Dynamic Earth http://pubs.usgs.gov/publications/text/fire.html
Could also be called Circum-Pacific Ring of Earthquakes
Subduction Zone beneath W.Latin America & Lesser Antilles
Earthquakes occur all along the subduction zone but those along the Seismogenic zone are most destructive
Flat Slab regions
allow for more
stress to build up between the plates(Gutscher
et al., 2000)
Normal (Steep) Slab
Flat Slab segments lack arc volcanoes Andes N. Volcanic Zone
Andes Central Volcanic Zone
Andes S. Volcanic Zone
Trans-Mexico Volcanic Belt
Flat Slab segments
in S. America(Gutscher
et al., 2000)
Top 5 Killer Volcanic Eruptions, WorldSince 1500AD, about 300,000 people have died as a result of volcanic eruptions
Volcano Country Year # deaths Cause 1) Tambora Indonesia 1815 92,000 Starvation2) Krakatau Indonesia 1883 36,000 Tsunami3) Mt. Pele Martinique 1902 29,000 Pyroclastic flow 4) Nevado del Ruiz Colombia1985 25,000 Mudflow5) Unzen Japan 1792 15,000 Debris avalanche
Deadliest eruptions in Latin America
Volcano Country Year DeathsNevado del Ruiz Colombia 1845 1,000Cotopaxi Ecuador 1877 >300Soufrire St. Vincent (L. Ant.) 1902 1,680Mount Pele Martinique (L. Ant.) 1902 29,000Santa Maria Guatemala 1902 ~1,500El Chichn Mexico 1982 >2,000Nevado del Ruiz Colombia 1985 25,000
Martinique, Lesser Antilles 1902
Volcanoes of the Lesser Antilles
MartiniqueColonized by France in 1635, the island has subsequently remained a French possession except for three brief periods of foreign occupation. 1100 sq. km (424 sq mi.)430,000 peopleHighest point is Mt. Pelee, 1400 m
M.R. = Morne Rouge
St. Pierre before 1902 eruption
St. Pierre before its Destruction
St. Pierre was the economic center of Martinique
During the year 1889, the reactivation of fumaroles is reported at the summit.In February 1902, strong sulfur smells are perceived, first in the vicinity of Prcheur, then in Fond Cor(North Saint-Pierre).April 1902
April 22nd, the telegraph cable between Martinique and Guadeloupe is broken.
April 24th, a column of black smoke arises from the crater, up to a height of 1600-1900 ft.
April 25th, the village of Prcheur is covered with ash. April 28th, strong rumblings are heard, as the vapor column
Pelee Chronology (contd.)May 1902
May 2nd, abundant ashfalls and dull rumblings can still be heard. The black column of vapor is furrowed with lightning. The first ashfall is reported on St.Pierre, and a thin layer of dust covers the whole island.
May 3rd, total darkness over Prcheur. Many inhabitants seek refuge in St. Pierre.
May 5th, one of the sides of the Etang Sec Crater suddenly falls apart, giving way to a devastating mudflow which destroys the sugar mill Gurin on the coast between St.Pierre and Prcheur. The first 25 deaths are reported.
May 6th, the telegraph cable between St.Pierre and St.Lucia is broken. Numerous glowing phenomena are observed over the crater.
May 7th, houses collapse and trees break down under the weight of the ash.
Why didnt the people of St. Pierre evacuate?
No volcanologists were on the island, and for the residents the only point of reference was the mild eruption of 1851-1852. The governor appointed a "Volcano Commission" with the most qualified specialists on the island : doctors, pharmacists, science teachers... The first meeting was held May 7th (the day before the city was destroyed)
First (and only) report of the St. Pierre Volcano Commission
The commission, responsible for the study of the Mount Pele's volcanic phenomena met yesterday evening, May 7th, under the chair of the Governor. After a careful analysis of the facts, the commission declares that:
1All the phenomena which have occurred so far are normal, and are commonly observed on all volcanoes around the world;
2Since the craters of the volcano are wide open, the expansion of the vapors will continue with no earthquake or rock projection;
3According to the location of the craters and the position of the valleys leading to the sea, the City of St. Pierre is perfectly safe.
Some people evacuatedSome people were afraid of the powerful phenomena which
took place between April and May 7th 1902. Some families moved away from the volcano, but those voluntary evacuations were quite limited. The travel records in the early morning of May 8th - a religious holiday-- shows that there were more people traveling to St. Pierre than people leaving the city !
The story of Captain Leboffe of the Italian bark Orsolinasuggests that the population of St. Pierre would have been saved if they had some knowledge about explosive volcanoes. The Italian captain was a native of Naples, and was quite familiar with the Vesuvius volcano. He hastily left the harbor of St. Pierre on May 7th, without his custom clearance, warning that "if Vesuvius looked like Mt. Pelee did, Naples would have been evacuated"..
Types of Eruptions: VulcanianA vulcanian eruption is a type of explosive eruption that ejects new lava fragments that do not take on a rounded shape during their flight through the air. This may be because the lava is too viscous or already solidified. These moderate-sized explosive eruptions commonly eject a large proportion of volcanic ash and also breadcrust bombs and blocks. Andesitic and daciticmagmas are most often associated with vulcanian eruptions, because their high viscosity (resistance to flow) makes it difficult for the dissolved volcanic gases to escape except under extreme pressure, which leads to explosive behavior.
Types of eruptions: StrombolianStrombolian eruptions are characterized by the intermittent explosion or fountaining of basaltic lava from a single vent or crater. Each episode is caused by the release of volcanic gases, and they typically occur every few minutes or so, sometimes rhythmically and sometimes irregularly. The lava fragments generally consist of partially molten volcanic bombs that become rounded as they fly through the air. The photo at right is a close view of StromboliVolcano erupting incandescent molten lava framgents.
Types of Eruptions: Plinian
Plinian eruptions are very explosive events that form enormous dark columns of tephra and gas that rise high into the stratosphere (>11 km). Such eruptions are named for Pliny the Younger, who carefully described the disastrous eruption of Vesuvius in 79 A.D. This eruption generated a huge column of tephrainto the sky, pyroclastic flows and surges, and extensive ash fall. This is a photograph of a plinian-
type eruption of Mount Spurr, Alaska. This sent an eruption column to a height of about 18 km above sea level
What is tephra?Tephra is a general term for fragments of volcanic rock and lava regardless of size that are blasted into the air by explosions or carried upward by hot gases in eruption columns or lava fountains. Tephra includes large dense blocks and bombs, and small light rock debris such as scoria, pumice, and ash.
Pyroclastic flowA pyroclastic flow is a ground-hugging avalanche of hot ash, pumice, rock fragments, and volcanic gas that rushes down the side of a volcano as fast as 100 km/hour or more. The temperature within a pyroclastic flow may be greater than 500 C, sufficient to burn and carbonize wood. Once deposited, the ash, pumice, and rock fragments may deform (flatten) and weld together because of the intense heat and the weight of the overlying material. Pyroclastic flows are sometimes called Nue Ardentes, French for glowing avalanche and are associated with PlinianeruptionsPhoto at right is a pyroclastic flow sweeping down the side of Mayon Volcano, Philippines, 15 September 1984. Note the ground-hugging cloud of ash (lower left) that is billowing from the pyroclastic flow and the eruption column rising from the top of the volcano.
Pyroclastic flows descend the flank of Mayon Volcano, Philippines. Maximum height of the eruption column was 15 km above sea level, and volcanic ash fell within about 50 km toward the west. There were no casualties from the 1984 eruption because more than 73,000 people evacuated the danger zones as recommended by scientists of the Philippine Institute of Volcanology and Seismology. http://volcanoes.usgs.gov/Imgs/Jpg/Mayon/32923351-020_caption.html
Colima (Mexico) Nue Ardente
Aerial view of Colima Volcano showing an eruption of a pyroclastic flow. The nue reached a maximum distance of 4.5 km from the summit. Photograph courtesy of Abel Cortes, ColimaVolcano Observatory,University of Colima, November 22, 1998.