TOP: Central peak (there are three) of Nevado del Huila volcano.
BOTTOM: The brown scars of landslides merge above Rio Paez. Nearly all of the landslides orginated on slopes of > 30°. Most began as shallow slips in water-saturated soil and liquefied immediately; heavy rains before the earthquake had saturated the steep hillsides. The slides typically were about 1-2 m thick. Near the earthquake epicenter, the landslides removed > 50% of the vegetation. Photograph by R.L. Schuster on 4 July 1994.
In volcano movies (my favorite is "Krakatoa, East of Java," because Krakatoa was west of Java), shrieking people flee from the fire, flowing lava and flying hot rocks.
But those aren't what usually kills people when a volcano goes bad. The most likely ways you're going to snuff it if the beautiful peaceful postcard mountain above you suddenly wakes up and declares itself to be a nasty volcano are:
* Gas -- poison, or at least not breathable
* Lava Flows
* Pyroclastic Flows
and I am tremendously embarrased to admit that I don't have a clue what Tephra is. I can Google, but if you know already, Leave A Comment. I don't want to be killed by something whose name I don't even know. If the p.a. announces that there's a Tephra, I'd like to know what that means so I can figure out what to do.
This week's world's most dangerous volcano, Nevado del Huila, is in the Andes/Cordillera in Colombia, South America. (Last week's was in nearby Ecuador.)
Nevado del Huilo is one of those Surprise Volcanos. Since the Spanish Conquistadores first came to Colombia around 1520, it's never erupted, everybody always classified it as either Dormant or Extinct or Not A Volcano At All.
Surprise. It's a Volcano. Flee for your lives.
The Associated Press
Thursday 19 April 2007
Colombia Volcano Erupts,
by Fernando Vergara
[image] The Nevado del Huila, which is topped with a crown of ice, is Colombia's third-highest peak at 18,484 feet. Located 170 miles southwest of Bogota, it became active again in March with a series of internal rumblings. "The seismic activity remains light but permanent, and we can't rule out another bigger event in the next hours or days," said Mario Ballesteros.
Thousands of people were evacuated after a long-dormant volcano erupted late Tuesday and again early Wednesday, provoking avalanches and floods that swept away houses and bridges.
The Nevado del Huila volcano's eruptions were its first on record since Colombia was colonized by the Spanish 500 years ago.
There are about 10,000 people living in the area around the volcano, and about 3,500 had been evacuated, Luz Amanda Pulido, director of the national disaster office, told The Associated Press after flying over the volcano in southwest Colombia.
There were no reports of deaths or injuries.
The eruption sent an avalanche of rocks down the volcano's sides and into the Paez and Simbola rivers, causing them to flood.
"The bridges were swept away, the highway used by the indigenous in the zone was destroyed for various kilometers (miles) and the problem we have now is the lack of a route to deliver goods and medicines to the population," Police Gen. Orlando Paez said.
Experts were not ruling out more eruptions.
"The seismic activity remains light but permanent, and we can't rule out another bigger event in the next hours or days," said Mario Ballesteros, director of the government's Institute for Geology and Mining.
The Nevado del Huila, which is topped with a crown of ice, is Colombia's third-highest peak at 18,484 feet. Located 170 miles southwest of Bogota, it became active again in March with a series of internal rumblings.
In 1985, the town of Armero was wiped from the map and 25,000 people were killed when another volcano, the Nevado del Ruiz, exploded and set off a series of mudslides. It was Colombia's worst natural disaster.
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© 2007 Associated Press/AP Online. All rights reserved.
Wednesday 18 April 2007
Colombian volcano erupts,
BOGOTA, 18 April (Reuters) -- Several thousand people were evacuated after a volcano erupted in southern Colombia, triggering an avalanche that swelled rivers and threatened local communities, authorities said on Wednesday.
Tumbling waters carrying trees, rocks and mud forced around 5,000 people to leave their homes for safer ground in the southern provinces of Huila and Cauca, local and emergency officials said.
"In the municipalities and departments where the avalanche passed we have no reports of any victims. We have some bridges down ... but people had time to evacuate," Civil Defense official Col. Hector Riveros said.
The Nevado del Huila Volcano erupted at the start of the year after laying dormant for hundreds of years. A eruption of the Nevado del Ruiz volcano in 1985 triggered mudslides killing 25,000 people in Colombia's worst natural disaster.
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United States Geological Survey
(US Department of Interior)
Volcano Hazards: | Types and Effects | Location |
| Gas | Lahars | Landslides | Lava Flows | Pyroclastic Flows | Tephra |
Earthquake on 6 June 1994
Triggers Landslides and Catastrophic Lahar
Near Nevado del Huila Volcano, Colombia
Landslide scars on hillslopes above R?o Paez, near Huila Volcano, Colombia
Photograph by R.L. Schuster on July 3, 1994
Brown-colored scars on steep hillsides sweep into the R?o Paez at the base of Nevado del Huila (elevation 5,262 m), a large volcanic complex in Colombia. The scars are pathways of dozens of landslides that removed wet soil, volcanic ash, and vegetation from the hillsides and produced a destructive lahar in the R?o Paez valley (flowing toward bottom of photograph). The southwest flank of the volcano is visible in upper left.
Within minutes of a magnitude 6.4 earthquake beneath the SSW flank of Nevado del Huila volcano, dozens of landslides swept from the steep valleys above R?o Paez into the river. The landslides quickly turned into debris flows, which joined to produce a single enormous flow of water, rocks, soil, and trees in R?o Paez. The lahar destroyed most or parts of several towns along the river, including Dublin, Irlanda, Toez, and Belalcazar, killed several hundred people, and displaced about 20,000 people from their homes. Six bridges and >100 km of roads were destroyed.
The huge flow wave originated from both hydrothermally altered rocks of Huila Volcano and the ash-mantled terrain surrounding the volcano. Whether triggered by a large earthquake, intense rainfall (for example, see Casita Volcano), or both, this tragic event illustrates that both volcanic cones and steep hillslopes around them can collapse to form landslides and debris flows.
People from around the world have repeatedly sensed an approaching lahar as a rumbling noise or ground vibration. In some cases, had they known the cause of the noise and tremor, people killed by lahars may have had time to get to high ground before it reached them. In the case of lahars triggered by a large earthquake, people often mistake the shaking of the ground from an approaching lahar as a second earthquake, and so they stayed where they were. People living in valleys downstream from mountainous volcanic terrains can reduce their risk by moving immmediately to high ground for a few hours after a strong earthquake--just in case a destructive flow is headed their way. This strategy is very important for communities located at the mouth of a tributary canyon, an area that can be swept by lahars from both the canyon and the main river valley.
Map of Nevado del Huila volcano and path of 1994 lahar in R?o Paez
Scars of landslides that merged together to form lahar on June 6, 1994 Brown scars mark landslide pathways on steep slopes above R?o Paez.
Close view of landslides that did not reach R?o Paez Some landslides did not contribute to the main lahar in R?o Paez.
R?o Paez and town of Islanda swept by lahar on June 6, 1994 Lahar traveled down R?o Paez and destroyed town of Irlanda.
Town of Irlanda, Colombia, swept by lahar on June 6, 1994 Closer view of main lahar at Irlanda.
Town of Toez hit by lahar, R?o Paez, Colombia Lahar overruns town of Toez within 10 minutes of the earthquake.
Town of Toez, Colombia, struck by earthquake and swept by lahar on June 6, 1994 Earthquake damages structures before lahar arrives.
Building hit by lahar on June 6, 1994, along R?o Paez, Colombia Tremendous impact force of the lahar hits barn and other structures.
Town of Belalcazar, largest community hit by lahar in R?o Paez, Colombia Town of Belalcazar, largest community hit by lahar in R?o Paez, Colombia.
Other landslides and lahars
* Otake Volcano, Japan
* Casita Volcano, Nicaragua
* Mount St. Helens, Washington
U.S. Department of the Interior, U.S. Geological Survey, Menlo Park, California, USA
Contact: VHP WWW Team
Last modification: 20 June 2002 (SRB)