Maarg Manthan · Topic 3.8

Extinct, Dormant and Active Volcanoes

Geography › Geomorphic Processes and Landform Evolution · Topic 3.8

Volcanoes are classed by how recently they have erupted. An active volcano has erupted in recent times, usually taken as the last 10,000 years (the Holocene), or shows signs of unrest such as gas emissions and tremors. A dormant volcano has not erupted for a long time but could erupt again. An extinct volcano is not expected to erupt again, since its magma supply has gone. The boundaries are fuzzy, and a volcano called extinct has sometimes come back to life.

5 min read · UPSC Prelims · Geography · Geomorphic Processes and Landform Evolution

At a Glance

Active Erupted in recent time; may erupt now
Dormant Quiet for long but could erupt
Extinct Not expected to erupt again
India’s active volcano Barren Island
India’s dormant volcano Narcondam
Exam link UPSC Prelims, Geography: Geomorphic Processes and Landform Evolution

Where Does It Fit?

This topic follows the study of volcanic landforms and classes volcanoes by their present state. It links directly with the hazards, monitoring and distribution covered in the topics that follow. Previous topic: Extrusive Volcanic Landforms: Geysers and Hot Springs. Next topic: Distribution of Volcanoes: Pacific Ring of Fire, Mediterranean Volcanism.

How Are Volcanoes Classified by Activity?

Class	Meaning	Examples
Active	Has erupted in historical time or the last 10,000 years, or shows unrest	Mount Etna and Stromboli (Italy), Kilauea and Mauna Loa (Hawaii), Merapi (Indonesia), Barren Island (India)
Dormant	Quiet now, but has erupted in the recent past and may erupt again	Mount Fuji (Japan, last erupted 1707), Vesuvius (Italy, last erupted 1944), Narcondam (India)
Extinct	No eruption in a very long time; the magma supply is cut off, and the cone is eroded	Arthur’s Seat (Scotland), Shiprock (USA); the volcanic hills of the Deccan

Scientists point out that these terms are not exact. Mount Pinatubo in the Philippines was thought to be dormant before it erupted violently in 1991. Because no one can be sure that a volcano is extinct, many volcanologists prefer the terms active or inactive, or speak of potentially active volcanoes.

How Many Volcanoes Are There?

Roughly 1,300 to 1,400 volcanoes are listed as having erupted in the last 10,000 years, and about 500 have erupted in recorded history. On average, around 50 to 70 volcanoes erupt in a year, and some erupt continuously. These figures are approximate and change as records improve, so the latest data from the Smithsonian Global Volcanism Program should be checked. A large share are on plate boundaries, as described in Distribution of Volcanoes: Pacific Ring of Fire, Mediterranean Volcanism.

What Is the Situation in India?

Barren Island: in the Andaman Sea, India’s only confirmed active volcano, with eruptions of ash and lava reported in the 1990s, 2000s and later years.
Narcondam Island: a small volcanic island in the Andaman Sea, classed as dormant. Some earlier sources call it extinct, so both terms may be seen.
Extinct features: the Deccan Traps, the Dhinodhar hills of Kachchh and the Rajmahal Traps are volcanic features of the past.

Both island volcanoes are part of the same volcanic arc that continues to Indonesia and result from the subduction of the Indian plate, as explained in Plate Boundaries: Divergent, Convergent, Transform.

Which Recent Eruptions Are Important?

The eruption of Eyjafjallajokull in Iceland in 2010 sent an ash cloud over Europe that grounded thousands of flights. The January 2022 eruption of Hunga Tonga-Hunga Haapai in Tonga, a submarine volcano, produced one of the most powerful atmospheric explosions in modern times, a global pressure wave and tsunamis across the Pacific. Mauna Loa in Hawaii erupted in November 2022 for the first time in about 38 years. Mount Semeru and Mount Merapi in Indonesia erupt repeatedly. In India, Barren Island in the Andaman Sea has had intermittent eruptions of ash and lava in recent years. As an analytical point, the global pattern of eruptions follows plate boundaries, and effusive eruptions are common at divergent boundaries and hotspots, while the more explosive ones occur at subduction zones, as shown in Distribution of Volcanoes: Pacific Ring of Fire, Mediterranean Volcanism.

How Are Eruptions Monitored and Predicted?

Volcanologists watch for signs before an eruption: small earthquakes caused by the rising magma, swelling or tilting of the ground measured by GPS and satellites, a change in gas emissions, particularly sulphur dioxide, and rising temperature. These signs allow warnings and evacuations, and they save lives, although the exact time and size of an eruption are hard to predict. Hazard maps and exclusion zones around active volcanoes depend on knowledge of past eruption styles. The effects of eruptions on people and climate are in the hazards of volcanoes.

Why Does Classification Matter for Safety?

A volcano that has been quiet for centuries can build up gas-rich magma that erupts with enormous force, as Vesuvius did in 79 CE and Pinatubo in 1991. People tend to settle around dormant and supposedly extinct volcanoes because their soils are fertile, which increases risk. Hazard maps, evacuation plans and warning systems are therefore made for any volcano with a history of activity. The effects and benefits of eruptions are in the topic on hazards of volcanoes in disaster management, and the lava types in Types of Lava: Andesitic (Acidic) and Basaltic (Basic) Lava. As an analytical point, classification is a tool for planning, and not a guarantee of safety.

Why Is This Topic Important?

Definitions Frequent Prelims question
India Barren Island and Narcondam
Safety Hazard planning

What Came Next?

The next topic maps where volcanoes occur on the Earth. Next topic: Distribution of Volcanoes: Pacific Ring of Fire, Mediterranean Volcanism.

Key People and Terms

Active volcano Erupted recently or shows unrest
Dormant volcano Quiet but may erupt
Extinct volcano Not expected to erupt
Holocene Last 11,700 years
Volcanic arc Chain of volcanoes at a subduction zone
Volcanology Study of volcanoes

Exam Corner

Points to Remember

Barren Island is India’s active volcano.
Narcondam is dormant.
Active usually means eruption in the last 10,000 years.
Pinatubo erupted in 1991 after centuries of quiet.
The terms are not exact.

Do Not Confuse With

Dormant and extinct May erupt again versus not expected to
Barren Island and Narcondam Active versus dormant
Active volcano and erupting volcano Recent history versus eruption now

Memory Hook

Active alive, dormant asleep, extinct dead, but check before you trust the bed.

Mains Angle

Questions ask for monitoring and risk reduction. These points add depth.

Uncertainty Classes are not exact
Monitoring Seismic and gas data
India Island arc volcanoes

A Question You May Face

An original practice question, not a past paper question.

“Distinguish between active, dormant and extinct volcanoes and discuss how volcanic eruptions are monitored.”

How to Answer

Define Three classes.
Examples World and India.
Limit Pinatubo.
Monitor Seismic, gas, satellite.

GS Relevance

Prelims: definitions, examples of active, dormant and extinct volcanoes, Indian volcanoes. GS Paper 1: volcanism; GS Paper 3: disaster management.

Frequently Asked Questions

What is an active volcano?

An active volcano is one that has erupted in the recent past, usually taken as the last 10,000 years, or one that shows signs of unrest such as earthquakes, gas emissions and ground swelling. Examples include Mount Etna, Kilauea and Barren Island in India, which is the only confirmed active volcano of the country.

What is a dormant volcano?

A dormant volcano is one that has not erupted for a long time but is expected to erupt again in the future. It may show some signs of activity. Mount Fuji in Japan and Narcondam island in the Andaman Sea are often cited as examples of dormant volcanoes.

What is an extinct volcano?

An extinct volcano is one that is not expected to erupt again because its magma supply has been cut off. Its cone is often eroded. Arthur's Seat in Scotland is an example. However, the label is not certain, since some volcanoes thought extinct have erupted later.

Which is the only active volcano in India?

Barren Island, in the Andaman Sea about 135 km northeast of Port Blair, is the only confirmed active volcano in India. It has erupted several times in recent decades, giving out ash and lava, while the nearby Narcondam island is classed as dormant.

How are volcanoes monitored?

Volcanoes are monitored with seismometers that detect small earthquakes, instruments that measure ground swelling, gas sensors and thermal sensors, and satellites that measure heat and deformation. Changes in these signals can warn of an eruption, though exact prediction of the time and size is still not possible.

PYQ Practice — Statement Analysis

1 Barren Island is an active volcano of India.

True

It lies in the Andaman Sea.

2 Narcondam is classed as an active volcano.

False

It is dormant.

3 An extinct volcano is certain never to erupt again.