Is Volcanic Ash Flammable? (A Comprehensive Overview)

In this article we will answer the following question: “Is Volcanic Ash Flammable?”, and other relevant inquiries that you may have about Volcanic Ashes.

Is Volcanic Ash Flammable?

Volcanic ash is made of inorganic compounds that can’t burn, are not combustible, and will not ignite if tossed in a fire. Volcanic ash is nothing like wood or coal ashes (but those aren’t flammable either), it is made mostly of tiny pieces of rock and sand.

What is Volcanic Ash?

Volcanic ash (volcanic dust) is made of tiny rough particles, mostly sharp-edged, of rocks, minerals, and sand. It is very abrasive, cannot be dissolved in water, is mildly corrosive, and can conduct electricity when wet.

It is not actual ash, like the fluffy white powder left in a fireplace, since it’s not a product of combustion.

Volcanic ash is formed during volcanic eruptions. When gases dissolved in the magma (molten rock) from within expand, they can find their way through the surface, escaping violently into the air or water, forming a characteristic towering eruption column.

Eruptions then force the gas in the rock particles to expand rapidly, breaking the magma particles into a dust-like pattern. Once airborne, the magma cools and turns into rock and glass fragments that can be blown away even thousands of kilometers away.

What is a volcano?

A volcano is a rupture in the crust of a planet that allows magma, gases, and volcanic ash, and it’s not something unique to our planet.

Volcanos are located near tectonic plates, they normally happen where tectonic plates are diverging or converging, but volcanism can also happen away from plate boundaries.

A volcano as an eruption occurring in a conical mountain is just one of the many forms it can happen. There are also ones with different kinds of peaks, and even landscape features. 

On some moons of Jupiter exists ice volcanos, called cryovolcanos; they happen because compounds like water, ammonia, and methane are ejected into a very cold environment, freezing instantly. 

Volcanic Ash Hazards

Volcanic ash may contain solutions of sulfur dioxide and chlorine, which can combine with the air to produce sulfuric acid and hydrochloric acid, as well as other chemicals that might be dangerous and corrosive for humans and planes, overall.

These ashes have a melting point below the operating temperature of modern plane’s turbine engines and are very abrasive, they can contaminate openings, be sucked into jet engines, and melt, so volcanic ashes are a major hazard for flight operations.

Volcanic ash can damage crops, can get stuck in roofs and make them collapse, can clog ventilation systems, contaminate water supplies, power stations, and telecommunications, and even lead to acid rain.

The dust can impact human and animal health, irritate and damage the lungs and eyes, posing a threat to people that have respiratory illnesses.

Prevention and mitigation

But there are many ways for people to protect themselves against volcanic ashes. Here are some:

  • First of all, this is just meant to add some knowledge to you. If a volcanic eruption is forecast or ash has fallen in your location, follow the advice of your local authorities.
  • Wear protective equipment like goggles and dust maks;
  • Sealing buildings so the dust can’t penetrate easily;
  • Do your best not to inhale any dust particles;
  • People with respiratory illnesses must remain safe at all times. They could evacuate to regions away from the volcano, but staying inside is always indicated;
  • Stay alert for low visibility on roads;
  • Wet dust particles to prevent them from spreading.

Volcanic ash properties

Volcanic ash may look harmless and soft, but it is actually made of tiny rock and sand particles, and they are very hard. Its structure is very porous and vesicular-like, so it also presents a low density, which explains its ability to travel long distances.

Volcanic ashes are insoluble in water, but when wet, they can acquire a consistency of slurry or mud, sticking to surfaces and making it more difficult to clean up. The material can adhere to sewer systems and other important human installations.

Structures of Volcanic Ash. The size is in the picture.

Source: Journal of Applied Geology

Volcanic ashes have a lot of pores that appeared after the eruption when the gases that were dissolved and stuck to the magma forced their way out. The pores are there because they once had held those gases, and due to the cooling effect after the outbreak.

The ashes properties depend on the style of volcanic eruptions. Magmas from different regions have different chemistry, crystal content, temperature and gases, and can be measured using something called Volcanic Explosive Index.

Chemical properties

As we said, the chemical constitution of volcanic ashes depends on the magma that originated it

At least 50% of the volcanic ashes are made of silica, which can contain other compounds such as iron and magnesium. The predominant gases released are water, carbon dioxide, hydrogen, sulfur dioxide, carbon monoxide, and hydrogen chloride.

Although the ashes are considered insoluble in water, a few ions and salts can be found in fresh ash leachates, such as: sulfates, chlorides, fluorides, sodium, potassium, calcium, and magnesium.

Physical properties

The physical components of volcanic ashes are small pieces of volcanic glass and pieces of other rocks.

Volcanic ashes are flammable?

No, they are not. Volcanic ashes are essentially made from inorganic compounds that can’t catch fire. But even if it had some organic compounds, they would have already burned since the magma reaches about 850ºC/ 1560ºF.

Even magma itself does not present any fire. We commonly associate hot and incandescent stuff with fire, but fire is a chemical reaction that can only happen with organic molecules.

What is fire?

Fire is heat and light. 

Although short, the answer above is quite complex. We often grow up imagining that fire is something glamorous, some kind of force of nature that science can’t comprehend, something that alchemists tried to glimpse centuries ago.

Nowadays, science has many tools to explore the structures of matter. In many cases, scientists can comprehend precisely how a chemical reaction happens, and what byproducts it produces, even at an atomic level (around 0,0000000001 meters / 10-10m).

Fire is the result of a chemical reaction, it is energy in the form of light and heat. This energy comes from the chemical bondings of the fuel that’s being burned. Combustion reaction has the byproducts: carbon dioxide, water, and energy, overall.

Organic molecules are the only things that can burn because combustion only happens to them. Combustion is not the only kind of chemical reaction that liberates heat, but it’s the most common one. Their energy is trapped within the chemical bondings.


In this picture, we present what some combustible substances look like. Note that they all have lots of carbons (C) and hydrogens (H). Sources of fuel often have carbon-carbon and carbon-hydrogen bondings, which can react with oxygen in combustion reactions.

These bondings possess a lot of energy within. When carbon and hydrogen break free to react with oxygen, they produce carbon dioxide (CO2) and water (H2O). The excedent energy is what we see and feel when around a fire.

Many things can break, mill, heat, melt, decompose and change in many ways when tossed in a fire, but it doesn’t mean that it will burn. The most important thing about combustion is that it generates heat, but not all chemical decompositions can do it.

So, what if we try to burn volcanic ashes?

Well, in essence, nothing will happen, not chemically. 

There’s nothing in volcanic ashes that would make them burn, and no significant thermal decomposition would happen unless you heat it really hard, around 800ºC. This is because volcanic ashes are basically powdery magma.

Also, heating volcanic ashes around 1,100 °C (2,010 °F) could make them melt and, like an intense source of heat, that would be a big fire hazard. But of course, the machinery you’ve used to reach those degrees would have become a fire hazard much sooner.

But this doesn’t mean that volcanic ashes are not harmful. Volcanic ash fall is physically, socially, and economically disruptive. Can prejudice human and animal health and poses a threat to human infrastructure, machinery, and transportation.


Volcanic ashes are not flammable, will not ignite and no flames would appear if we heat really hard or toss them into a fire. Volcanic ashes can melt but only after 1000ºC, and present no fire hazard if it is not hot.

Frequently Asked Questions (FAQS): Is Volcanic Ash Flammable?

Is volcanic ash toxic?

Yes, it can be. Volcanic ashes may contain toxic compounds, especially fluorine, chloride and sulfuric gases. The ashes can affect human respiratory systems and even lead to death by asphyxiation. The particles are glassy and can damage our skin.

is volcanic ash good for soil

Volcanic ash may contain some secondary nutrients that are important to the soil such as magnesium, calcium, sodium, sulfur, copper, iron, and zinc. They are called secondary because the soil requires just a bit of it, not because they’re less important.

But at the same time, secondary nutrients can’t be in excess in the soil, otherwise, they might jeopardize the other nutrients, so it’s hard to measure how much of it a garden could receive as fertilizer.

Another important characteristic of these ashes is that they might be acid, which is not good for most gardens. 

Overall, volcanic ash is something that might serve as a fertilizer, but it’s hard to measure how to use it, especially since no volcanic ash is like another. There’s still research required in this field.

is volcanic ash good for skin

Crude volcanic ashes are surely not good for your skin. However, cosmetic products that use volcanic ashes as one of their ingredients are safe because they had undergo a series of trials to assess their safety (unless it’s not a licensed product).


Budiman Minasny, Dian Fiantis, Kurniatun Hairiah, Meine Van Noordwijk, Applying volcanic ash to croplands – The untapped natural solution, Soil Security, Volume 3, 2021, 100006, ISSN 2667-0062,,and%20conducts%20electricity%20when%20wet.

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