ENVIRONMENT
What is volcanic ash? Why is it such a hazard? Check out our great encyclopedic entry to find out.
Teachers, scroll down for a quick list of key resources in our Teachers Toolkit, including today’s MapMaker Interactive map.

Photograph by Bernal Saborio, courtesy Flickr. CC BY-SA 2.0
Discussion Ideas
- Turrialba, a volcano in central Costa Rica, is ejecting volcanic ash more than a mile into the atmosphere. What is volcanic ash? Read through our encyclopedic entry for some help.
- Volcanic ash is made of tiny fragments of jagged rock, minerals, and volcanic glass. Unlike the soft ash created by burned wood, volcanic ash is hard, abrasive, and does not dissolve in water.
- Ash is a product of explosive volcanic eruptions. When gases inside a volcano’s magma chamber expand, they violently push molten rock (magma) up and out of the volcano. The force of these explosions shatters and propels the liquid rock into the air. In the air, magma cools and solidifies into volcanic rock and glass fragments—ash. Eruptions can also shatter the solid rock of the magma chamber and volcanic mountain itself. These rock fragments can mix with the solidified lava fragments in the air and create an ash cloud. Check out this amazing video of an ash cloud emitted from the eruption of Eyjafjallajokull, a glacier-covered volcano in southern Iceland.
- Our encyclopedic entry says volcanic ash can be ejected with enough force to reach the stratosphere, where it can reflect incoming solar radiation and absorb outgoing land radiation, leading to a cooling of the Earth’s temperature. Is the ash from Turrialba reaching the stratosphere—are we in danger of a “volcanic winter”?
- No! Ash from Turrialba is reaching heights of about 3,000 meters (9,840 feet), high enough to interfere with aircraft. But the stratosphere is about 7,000 meters (22,966 feet) higher than that—it takes a volcano a lot more powerful than Turrialba is right now to reach those heights. (Here’s one.)
- The Nat Geo News article reports that flights to Costa Rica’s capital, San Jose, have been diverted due to Turrialba’s ash. How might volcanic ash interfere with aircraft? Check out our encyclopedic entry for some help.
- In addition to limiting visibility, the small, abrasive particles of rock and glass can melt inside an airplane engine and solidify on the turbine blades—causing the engine to stall. Yikes.
- The Nat Geo News article reports that hundreds of people have gone to the hospital with breathing difficulties associated with Turrialba’s ash cloud. How might volcanic ash impact human health? Check out our encyclopedic entry for some help, or ask the people of Pompeii.
- If inhaled, volcanic ash can cause breathing problems and damage the lungs. Inhaling large amounts of ash and volcanic gases can cause a person to suffocate. (Suffocation is the most common cause of death associated with a volcano.)
- Carbon dioxide and fluorine, gases that can be toxic to humans, can collect in volcanic ash. The resulting ash fall can lead to crop failure, animal death and deformity, and human illness.
- Ash’s abrasive particles can scratch the surface of the skin and eyes, causing discomfort and inflammation.
- The Nat Geo News article says that “[w]hen a stratovolcano explodes, toxic gases and hot volcanic fragments can race down the mountainside with hurricane force.” What is this phenomenon called? Read through our encyclopedic entry for some help, or, again, ask the people of Pompeii.
- These volcanic avalanches are called pyroclastic flows. Reaching speeds greater than 100 kilometers per hour (60 miles per hour) and temperatures between 200° and 700° Celsius (392° and 1292° Fahrenheit), pyroclastic flows are considered the most deadly of all volcano hazards.
Nat Geo News describes Turrialba as an active stratovolcano, influenced by the interaction of tectonic plates. How are tectonic plates interacting beneath Turrialba? Take a look at today’s MapMaker Interactive map for some help.
- The Cocos plate (west) and the Caribbean plate (east) have a convergent boundary, meaning they are crashing into each other. The Cocos plate is subducting beneath the Caribbean plate. (Subduction! Our favorite geologic phenomenon.)
TEACHERS TOOLKIT
Nat Geo: This Volcano Is Spewing Ash Nearly Two Miles High
Nat Geo: What is volcanic ash?
Nat Geo: Where is Turrialba? map
Smithsonian Institution: Global Volcanism Program—Turrialba
Nat Geo: Eyjafjallajokull’s Volcanic Ash
Nat Geo: What is a pyroclastic flow?
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