Unit 16 GEOS

1. Which parts of Latin America have dangerous volcanoes? Why?

  • “Ring of fire”

2. What is a Nueé Ardente?

  • A nueé ardente (French for “glowing cloud”) is a pyroclastic flow—a fast-moving avalanche of hot ash, gas, and volcanic debris.

  • It rushes down volcano slopes at speeds over 100 km/h and temperatures over 500°C, incinerating everything in its path.

3. What is a lahar?

  • Is a rapidly flowing mixture of rock debris and water that originates on the slopes of a volcano 

4. What relationship is there between Latin American Flat Slab and volcanism?

  • Flat slab segments are areas where the subducting oceanic plate descends at a shallow angle.

  • These zones lack active volcanism because the slab doesn’t reach depths where melting occurs.

  • Found in Peru, Bolivia, and Central Chile, they are linked to stronger earthquakes due to increased plate coupling.

5. What were the two deadliest volcanic eruptions in Latin America? About how many people died?

  • Nevado del Ruiz; Colombia; 1985~25,000

  • Mount Pelée; Martiniqui; 1902~29,000

6. What were some of the early signs of volcanic activity in Mont Pelee?

  • Fumaroles at the summit come to life

  • Strong sulfur smells are perceived in north Saint-Pierre

  • Telegraph cable between Martinique and Guadeloupe is broke

7. What are the main types of eruptions, e.g., Vulcanian, Strombolian, and Plinian. 

  • Vulcanian:Moderate explosions of viscous lava, ash, and volcanic bombs

  • Strombolian:Rhythmic bursts of basaltic lava and gas from a single vent

  • Plinian:Massive, explosive eruptions with tall ash columns and pyroclastic flows

8. What is tephra?

  • refers to all volcanic material ejected into the air—ash, pumice, scoria, bombs, and rock fragments.

9. What is a pyroclastic flow?

  • A pyroclastic flow is a ground-hugging surge of hot ash, gas, and debris.

  • It’s deadly due to extreme heat and speed, often triggered by Plinian eruptions.

10. What is an ash fall?

  • Ash fall occurs when fine volcanic ash is ejected into the atmosphere and settles over large areas.

  • It can collapse roofs, contaminate water, and disrupt air trave

11. Where is Nevado del Ruiz and how did its eruption kill people?

  • Located in the Andes, near Armero.

  • In 1985, a small eruption melted glacier ice, triggering a lahar (volcanic mudflow) that buried Armero and killed ~25,000 people.

12. Where is Martinique and how did its eruption kill people?

  • Martinique is a French island in the Lesser Antilles.

  • In 1902, Mount Pelée erupted with a nueé ardente that destroyed St. Pierre, killing ~29,000 people in minutes.

  • Only a few survived, including Cyparis, who was protected inside a jail cell.