Classification of Volcanoes
Volcanoes based on Continuity of Eruption
Just like living beings, volcanoes go through different phases in their lifetime—some are young and full of fire, some slumber for centuries, and others fade into history, never to awaken again. Based on their activity, volcanoes are classified into three main types: Active, Dormant, and Extinct.
1. Active Volcanoes 🔥
These are volcanoes that have erupted at least once in the past 10,000 years and may still erupt in the future. Some remain in a constant state of activity, while others erupt sporadically over time.
Think of them as restless warriors, constantly spewing fire and reshaping landscapes. Most active volcanoes are found along the Mid-Oceanic Ridge (MOR), where tectonic plates are pulling apart, allowing magma to rise.
Examples:
- Mount Etna (Italy) – One of the most active volcanoes in the world, continuously erupting for centuries.
- Stromboli (Italy) – Known as the “Lighthouse of the Mediterranean” due to its constant glow from frequent eruptions.
- Kilauea (Hawaii, USA) – A shield volcano that has been erupting almost continuously for decades.
2. Dormant Volcanoes 😴
Dormant volcanoes are like deep sleepers—silent for centuries but still capable of waking up. These volcanoes haven’t erupted for a long time but are expected to erupt again in the future.
Think of them like a pressure cooker—quiet on the surface, but slowly building up heat and energy deep inside. When the conditions are right, they can erupt with immense force.
Examples:
- Mount Vesuvius (Italy) – Famous for burying Pompeii in 79 AD, it has remained mostly quiet but could erupt again.
- Mount Kilimanjaro (Tanzania, Africa) – This majestic, snow-capped peak is dormant but could awaken in the future.
3. Extinct Volcanoes ⛰️
Extinct volcanoes are those that have not erupted for at least 10,000 years and are highly unlikely to erupt again. Their magma chambers have cooled and solidified, making further activity almost impossible.
Think of them as old storytellers, their fiery past written in rock layers, but their days of eruption long behind them. Over time, erosion wears them down, turning them into rolling hills or even flat plains.
Examples:
- Mount Buninyong (Australia) – A long-dead volcano, now covered with lush greenery.
- Arthur’s Seat (Scotland) – A rocky peak near Edinburgh, once a volcano, now a peaceful tourist spot.
The Ever-Changing Nature of Volcanoes
A volcano classified as extinct today might not stay extinct forever. Earth’s geology is constantly evolving, and in rare cases, even long-dormant or supposedly extinct volcanoes have reawakened!
For instance, Mount St. Helens (USA) was thought to be relatively inactive before its catastrophic eruption in 1980. This proves that our planet is always shifting, always changing—making volcanism one of the most fascinating and unpredictable natural phenomena.
Volcanoes based on Nature of Eruption 🌋🔥
Not all volcanic eruptions are the same. Some flow gently like honey, while others explode with the force of a thousand bombs. The nature of an eruption depends on several factors—the composition of the lava, the amount of gas trapped inside, temperature, and pressure. Based on these characteristics, volcanic eruptions can be classified into three types: Quiet, Intermediate, and Violent.
1. Quiet Eruptions 🏞️
Imagine pouring warm honey onto a plate—it spreads smoothly without resistance. This is how quiet eruptions behave. The lava is basaltic, meaning it is highly fluid, low in silica, and holds little gas. Since it is not sticky, it flows easily, forming vast lava plains and shield volcanoes.
Key Features:
✔️ Lava flows freely without explosions.
✔️ Produces extensive lava fields.
✔️ Common in mid-ocean ridges and hotspot volcanoes.
Example:
- Hawaiian Volcanoes (e.g., Mauna Loa, Kilauea) – These volcanoes continuously release lava in a smooth and gentle manner, slowly expanding the land.
2. Intermediate Eruptions – The Unpredictable Ones 🌋⚡
Now, imagine shaking a bottle of soda and then opening it. The gas escapes with an initial burst, but after a while, it calms down. This is how intermediate eruptions work. They start with an explosion, releasing ash and gases, but gradually settle down into a steady lava flow.
Key Features:
✔️ Begins with explosive eruptions.
✔️ Followed by quieter lava flows.
✔️ Common in subduction zones where oceanic plates sink beneath continental plates.
Example:
- Mount Fuji (Japan) – A stratovolcano that has erupted violently in the past but also produces lava flows.
3. Violent Eruptions 💥
Now, picture a pressure cooker with a blocked steam outlet—so much pressure builds up that it eventually bursts. This is what happens in violent eruptions. The lava in these volcanoes is acidic, high in silica, and extremely viscous (thick). It traps gas inside, increasing pressure until the volcano blows apart violently.
These eruptions produce pyroclastic materials—deadly clouds of ash, lava fragments, and gases moving at hurricane speeds, destroying everything in their path.
Key Features:
✔️ Highly explosive eruptions.
✔️ Thick lava with high viscosity.
✔️ Produces pyroclastic flows (superheated clouds of ash, lava, and gases).
✔️ Creates massive destruction.
Examples:
- Mount Vesuvius (Italy) – In 79 AD, its explosion buried the city of Pompeii under a thick layer of ash.
- Mount St. Helens (USA) – Its 1980 eruption was one of the most destructive in modern history.
Volcanoes based on Mode of Eruption 🔥🌋
When a volcano erupts, it can do so in two distinct ways: through a central vent or along fissures in the Earth’s crust. This gives rise to two primary types of volcanic eruptions:
- Central-Type Eruption – Lava emerges through a single central pipe or vent. This type can range from gentle lava flows to violent explosions.
- Fissure-Type Eruption – Lava seeps out through cracks (fissures) in the Earth’s surface, often forming vast lava plains rather than volcanic cones.
Let’s see through the spectacular varieties of volcanic eruptions, each with its own signature style.
🌋 Central-Type Eruptions
These volcanoes erupt through a central vent, and depending on lava viscosity and gas content, they can be gentle or violently explosive.
1. Hawaiian-Type 🌊🔥
Imagine a pot of honey slowly overflowing from its rim—this is the Hawaiian-type eruption. The lava gently pours out of the crater and flows down the slope like a glowing river.
🔹 Key Features:
✔️ Lava is basaltic (low in silica) → highly fluid, flows easily.
✔️ No explosion, just continuous lava outpouring.
✔️ Forms shield volcanoes with wide, sloping sides.
🔹 Example:
- Mauna Loa & Kilauea (Hawaii, USA) – Some of the world’s largest and most active volcanoes, known for their gentle yet unstoppable lava flows.
- Ash plume 2. Lava fountain 3. Crater 4. Lava lake 5. Fumaroles 6. Lava flow 7. Layers of lava and ash 8. Stratum 9. Sill 10. Magma conduit 11. Magma chamber 12. Dike
2. Strombolian-Type 🎆🌋
Now, picture a champagne bottle being uncorked—bubbles rise, pressure builds, and suddenly, pop! This is how Strombolian eruptions work. The lava contains trapped gas bubbles (gas slugs) that burst every 10-15 minutes, creating small but regular explosions.
🔹 Key Features:
✔️ Lava is basaltic (less mobile but more viscous than Hawaiian lava).
✔️ Rhythmic eruptions—like nature’s own fireworks show.
✔️ Produces volcanic bombs (glowing blobs of lava).
🔹 Example:
- Stromboli (Italy) – Also called the “Lighthouse of the Mediterranean” due to its regular, glowing eruptions visible to passing ships.
- Ash plume 2. Lapilli 3. Volcanic ash rain 4. Lava fountain 5. Volcanic bomb 6. Lava flow 7. Layers of lava and ash 8. Stratum 9. Dike 10. Magma conduit 11. Magma chamber 12. Sill
3. Vulcanian-Type – The Explosive One 💣🌋
Imagine a cork stuck in a shaken soda bottle—when it finally pops, the soda explodes outward in all directions. Vulcanian eruptions occur when highly viscous magma traps gas pressure until it suddenly bursts in an explosion.
🔹 Key Features:
✔️ Highly viscous lava (andesitic, not basaltic).
✔️ More violent than Strombolian eruptions—produces large ash clouds.
✔️ Ash columns can reach 5-10 km into the sky.
🔹 Example:
- Volcano Vulcano (Italy) – The type example of this eruption, giving its name to all volcanoes.
- Ash plume 2. Lapilli 3. Lava fountain 4. Volcanic ash rain 5. Volcanic bomb 6. Lava flow 7. Layers of lava and ash 8. Stratum 9. Sill 10. Magma conduit 11. Magma chamber 12. Dike
4. Vesuvian (Plinian) Eruption 💀🌪️
These are characterized by extremely violent eruptions of lava which is highly charged with gases, possessing a relatively high degree of viscosity, during a long period of superficial quiescence.
🔹 Key Features:
✔️ Extremely violent eruption.
✔️ Lava is rich in gas and highly viscous → cannot flow easily, so it blows up instead.
✔️ Can create pyroclastic surges—deadly hot clouds that move at hurricane speeds.
🔹 Example:
- Mount Vesuvius (Italy, 79 AD) – Buried Pompeii and Herculaneum in a thick layer of ash, preserving history under volcanic dust.
1. Ash plume 2. Magma conduit 3. Volcanic ash rain 4. Layers of lava and ash 5. Stratum 6. Magma chamber
5. Pelean-Type – The Deadliest of Them All ☠️🔥
Now, imagine a pressure cooker that explodes sideways instead of upwards. Pelean eruptions are the most dangerous of all. They produce pyroclastic flows—superheated clouds of gas, ash, and lava fragments that race down the slopes at 700 km/h, destroying everything in their path.
🔹 Key Features:
✔️ Most violent and deadliest eruptions.
✔️ Produces lava domes instead of large cones.
✔️ Generates pyroclastic flows (superheated avalanches of ash and gas).
🔹 Example:
- Mount Pelée (Martinique, 1902) – Its pyroclastic flow destroyed the entire city of Saint-Pierre, killing 30,000 people in minutes.
1. Ash plume 2. Volcanic ash rain 3. Lava dome 4. Volcanic bomb 5. Pyroclastic flow 6. Layers of lava and ash 7. Stratum 8. Magma conduit 9. Magma chamber 10. Dike
🌍 Fissure-Type Eruptions – The Lava Floods 🌊🔥
While central-type eruptions occur from a single opening, fissure eruptions happen along cracks (fissures) in the Earth’s crust. Instead of forming volcanoes, they release massive lava sheets that cover large areas.
🔹 Key Features:
✔️ No volcanic cone, just vast lava plains.
✔️ Basaltic lava—flows over huge distances.
✔️ Creates lava plateaus instead of mountains.
🔹 Example:
- Deccan Traps (India) – One of the largest lava flows in history, covering 500,000 square kilometers. Formed around 65 million years ago, possibly contributing to the extinction of the dinosaurs.
