Volcanoes Are Hot Stuff

What Is a Volcano?

Credit: José F. Vigil, for This Dynamic Planet, USGS.

To understand volcanoes, you need to know that the Earth is not solid, but has a rocky crust over a hot, molten interior. The crust is divided into "tectonic plates," huge slabs carried along in slow motion by the roiling currents below.

Non-volcanic mountains are wrinkles in the Earth's crust, formed by immense pressures causing the plates to buckle. Volcanoes are holes in the crust where hot, molten rock (magma) from the Earth's interior bubbles up through cracks and bursts out onto the surface.

Most volcanoes rise along plate boundaries. A few volcanoes form over mid-plate "hot spots" where a fixed plume of hot magma builds a string of volcanoes as a plate passes over it.

So the difference between regular mountains and volcanoes is that mountains are formed by the earth's crust wrinkling or buckling, while volcanoes are formed when magma gushes out (magma is called lava on the surface).

Volcanoes FAQ

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Q: How hot is a volcano?
A: It varies, but here's a couple figures. Fresh lava erupting from Kilauea Volcano is around 2000° F (1100° C), while pyroclastic flows (avalanches of superheated gas, lava, and ash) can reach 1500° F (815° F). [Source: CVO] Also see this Diagram of lava temperatures from the USGS.

Q: Can scientists predict when a volcano will erupt?
A: Geologists can usually tell when a volcano is threatening to erupt by monitoring small earthquakes, the swelling and shrinking of the mountain, gas emissions and heat. But that data only provides probabilities, not a timetable. It's like trying to predict when a heavy raincloud will drop its rain.

Q: What causes a "hot spot"?
A: Volcanologists are still trying to figure this one out. It's easy to understand why volcanoes form along plate boundaries, but what makes a hole smack dab in the middle of a plate? I like the theory that hot spots are the scars of old asteroid impacts, but that idea is hotly debated.

Q: How do you pronounce that Icelandic volcano's name?
A: Badly. :) Here's two videos of Icelanders trying to help us learn this tongue twister: Eyjafjallajökull Pronunciation and Eyjafjallajökull: You're Doing It Wrong!

Volcanic Ash and Airplanes

Just how dangerous is volcanic ash to airplanes? I collected these links in 2010 during the height of the air traffic stoppage over Europe. Read them and see what you think:

• Video interview with aerospace engineer about 2 jets that almost crashed
• Video demonstration of volcanic ash damaging a jet engine
• Article: "How Volcanic Ash Can Kill an Airplane", with photos of damaged DC-10.
• Newsweek Article: Some Alaskan pilots can deal with volcanic ash
• BBC Article: Why the no-fly ban over Europe was lifted

Why I Made This Site

I am painfully aware of the hazards of volcanoes and the hardships they cause: homes and communities destroyed, lives lost, the economic and human cost. Nevertheless, I became hooked on volcanoes in 1986 after witnessing a spectacular eruption of Pu'u O'o on Kilauea from 7 miles away. I got in the habit of following that eruption, which is ongoing, and that led me to an armchair interest in volcanoes in general.

As a sometime teacher— in humanities, not science, although my parents are scientists— I enjoy sharing what I've learned. Volcanoes are, in my opinion, the most amazing phenomenon on the planet barring life itself, and they remind us that our planet, too, is alive.

Volcanology Humor T-Shirts

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