A Writer’s Guide… to Volcanology

This is part of the series of blog articles called “A Writer’s Guide…”, check out this article by writer L.B.Carter on Volcanology.

A Writer's guide to volcanology. Image: Volcano lava


(no, not the Star Trek kind)

by L.B.Carter

Vulcans? No, the study of volcanoes

First caveat: I’m not technically a .volcanologist (again, no, not the pointer and middle finger and ring and pinky finger v-shaped salute that belongs with Spock. That’s Vulcans with a “u”; this is the study of volcanoes). I’m a high-temperature geochemist and petrologist (study of igneous—made from lava—rock formation).

What the heck is a petrologist and how is it different?

That essentially means that I study what’s happening underground before the actual eruption part of a volcano, including magma (the word for lava when it’s underground) generation deep underground, rock melting, its chemistry, and ultimately what types of lava and volcanic gases should be expected at the surface.

Volcanologists, in the technical sense study the physical side of eruptions (rather than chemistry) and focus largely on understanding, for example, eruption intensity, ash formation and fallout, and hazards.

Volcanology is intermingled with human populations

However, I do also have a masters in natural hazards with a focus on volcanoes, so I know some of this side of things too, having studied under the volcanology gods.

I spent a few weeks with Guatemala hiking up active volcanoes (hard hats required in case they decide to spontaneously burp up any fresh rocks) with the country’s head volcanologist to inspect eruption deposits and risks to the locals.

First and foremost, I can say that this was an amazing experience, but secondly, I can say it was devastating. The largest issue with natural disasters is not nature’s wrath, but rather economic status.

Only the poorest communities were perched on volcano flanks, in the direct path of oncoming dangers like lahars (discussed below) and most of them did not have the education to understand the risk and also did not have the means to either move or be warned of the risks.

At one location, the Head Volcanologist described a phone tree system he had where he would call the landline of the person at the top of the slope and they would call the next and so on.

It was a simple solution when most don’t have other means of communication, but the issue with that is volcanic hazards can move much faster than humans.

Volcanoes are dangerous—and not because of lava

So, what are the hazards?

Lava flows

The news and movies like to fixate on lava flows. While pretty and mesmerizing, these are some of the least destructive aspects of volcanoes.

They move incredibly slowly (usually one can outwalk, let alone out run them), which is why Hawaii was successfully evacuated in the spring of 2018 and financial burden was a result of structural damage, not human life.

There are two kinds of lava flows.

  1. If you want to describe the kinds at Hawaii and Iceland where the lava is red-hot and very runny, it’s called Pahoehoe (pa-hoy-hoy) and form a ropey goopy texture. This lava (basalt) tends to cool into black rock (black or green sand beaches).
  2. Another kind, more common, is more viscous (measurement of stickiness—honey is more viscous than water) and so doesn’t flow as smoothly. Most volcanoes on land (e.g., Mt St Helens in Washington state, Vesuvius in Italy that destroyed Pompeii) have this kind of lava (andesite or rhyolite—or, when magma chambers cool slowly within the Earth without erupting, it’s called granite) which is much stickier and clumps into chunking and churning flows.

Because of this stickiness, when a volcano with this lava erupts, it tends to be much more violent. Basalt oozes out in flows. Rhyolite explodes into tiny fragments.


This means different kinds of hazards—fine-grained ash (which is a health hazard because you can breathe it in and a structural hazard because it’s very heavy when it settles on roofs and when it mixes with water it forms rapidly-hardening cement), columnar plumes which rise into the stratosphere and affect airplane travel.

Pyroclastic Flows

These plumes can also collapse again. This forms what’s called a pyroclastic flow or pyroclastic density current (PDC).

Seen that trailer from Jurassic World 2 where the island erupts and Chris Pratt’s character is sprinting down a hill with lots of dinosaurs and there’s a huge cloud of dark smoke chasing him?

That’s a PDC. And contrary to what that film insinuates, one cannot outrun those. They travel at over 100 MPH, are over 1000 degrees F and are made up of toxic gases like carbon dioxide, carbon monoxide and sulfur.

Have you seen those body casts of Pompeii? That entire city was destroyed by PDCs, which first burned and asphyxiated the people from the inside out (most were frozen with hands over their mouths) and then all the ash and particulates entrained in the cloud coated them and melded together (remember, they’re just small pieces of lava, so they are still somewhat molten and cool to form a shell).


I also mentioned lahars. These are hot mud-rivers essentially, when water mixes with fresh, hot ash and carries it downhill.

Because they’re so much thicker (denser) than water as a slurry, they can carry much heavier objects than a typical river and tend to form suddenly in a sweeping flood that traverses downstream.

They pick up boulders, cars, houses, smash bridges and when they stop flowing, they dry into cement.

These don’t have to occur during an eruption, but are common in areas where there’s snowcaps or ice that can melt during an eruption.

They may occur days after an eruption during an area’s rainy season (as happened with Fuego volcano in Guatemala in the summer of 2018, which paused rescue efforts from the initial eruption).

Heard of Supervoclanoes? VEI denotes eruption intensity

The final thing to mention about volcanoes is intensity and monitoring.

A volcano’s intensity is measured, like the Richter scale for earthquakes (which, by the way sometimes are associated with volcanoes as fresh magma under a volcanic edifice rises, cracking the rocks in the Earth’s crust as it travels upward through fissures), with a Volcanic Explosivity Index scale (VEI) that works exponentially, so 2 is 10 times more intense than 1.

There are a few factors that go into how eruptions are labeled, but the result is mostly, the higher the VEI, the more dangerous. Supervolcanoes are the highest and we have very few of them in recorded history—Toba in the Philippines and Yellowstone in the US.

Mount Tambora in Indonesia was a very intense eruption in 1815 which was so strong, the ash particles and sulfur that made it into the atmosphere actually blocked out a lot of the sun for the year following (1816), making the “Year without a Summer” in which Mary Shelly and a bunch of other darker authors wrote a few notable works (fun fact for you authors!

The weather can affect the mood—and success—of your books). This in turn caused famine and thousands of more deaths around the world long after the eruption ended.

Fear not, volcano monitoring exists in most countries

Most countries have governmental monitoring agencies. In the US it’s the United States Geological Survey (USGS), which has 5 observatories.

Hawaii Volcano Observatory (HVO) is the most robust with many scientists and monitoring devices.

They use seismometers to measure ground movement, satellites to measure when the ground inflates (magma injection underground), tools they can take to the edge of a vent to measure gas emissions (more CO2 and S means new magma and maybe an impending eruption).

And they have volcanologists and petrologists who go out and map where flows go (by doing so, we can better predict where future dangers might flow) as well as measuring lava composition (changes can mean new magma injection at depth).

They have an alert system for warning locals and the government, which can be found online or emailed.

There is also an international alert system for airspace to prevent airplanes flying into ash clouds and causing engine failure (as happened in Alaska airspace which spurred the formation of this alert system).

Final warnings about writing about volcanoes—AKA errors that make me blow my top

My final parting pet peeves about volcanoes: craters are the result of meteorite impact. Calderas are when a magma chamber evacuates (erupts), leaving a vacuum in the crust, which then collapses in.

Vents or lava lakes are the openings of volcanoes, and honestly not many volcanoes have a permanently open peak.

Quick overview of where volcanoes (magma) come from

And for a quick geology of the Earth: it’s broken up from surface to interior in 3 layers.

  1. crust (where magma travels through and is stored in chambers),
  2. mantle (the thickest layer, which is—fun fact—green rock, not red and molten for the most part; though this is where magma forms when this green rock melts due to heat at depth),
  3. and core (which has an inner solid and outer liquid layer and generates a lot of the heat that causes melting and makes it to the surface.

The convective motion in the outer core, caused by that heat—like boiling water roiling in a bot—is also what generates Earth’s magnetic field.

And the heat at the core causes convection in the mantle, which moves the tectonic plates around. This, in turn, forms volcanoes, because when plates collide, one can slide under the other, sinking into the hot mantle until it melts. The melts then rise back to the surface due to buoyancy and erupt).

Volcanoes aren’t always the antagonist

  1. Vacations

They’re a force to be reckoned with but without volcanoes, we wouldn’t have land on which to live—or the Hawaiian, Caribbean and Canary Islands to vacation to!

  1. Coffee

They’re also incredible useful for bringing fresh nutrients and ingredients to the surface—great for agriculture (writer’s sustenance—coffee—is usually grown on volcanic slopes).

  1. Air to breathe (kinda important)

And it’s thought that billions of years ago, volcanoes originally spit out the gases that make our atmosphere habitable, like oxygen and enough carbon dioxide to keep Earth stable at an average temperature that sustains life (long-term climate control; today humans far exceed volcanic emissions and thus have a greater effect).

  1. Jewelry and computer parts for typing on

Magma plumbing underground deposits precious ores like gold and trace metals that are important for technology, plumes bring diamonds up from deep in South Africa, the heat provides geothermal energy, and once they’re cooled, miners excavate old magma for your countertops.

Have fun with these hot intrusive bodies that make the bedrock 😉

So, if you want to play with volcanic disasters, you have a wealth of options, not just lava bombs (big pieces of lava shot out of volcanoes) or flows. If you have any further questions, feel free to contact me at my author website or check out my science twitter: @VolcaNerd and blog: “Outpourings of a VolcaNerd”.

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About L.B. Carter

Author L.B. CarterL.B. Carter is a Freelance Editor and Indie Author of the 2018 Best Indie Sci-Fi Nominee upper YA/NA Climatic Climacteric Series, Adult Suspense/Thriller and Dark Urban Fantasy who daylights as a scientist with a Ph.D. in Earth, Environmental and Planetary Sciences from Rice University with a specialty in geochemistry, petrology and volcanology.

She’s also a cat-mom and lover of spiced hot chocolate, polka dots and fairy lights.

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