Distribution of Volcanoes: Pacific Ring of Fire, Mediterranean Volcanism

At a Glance

• Ring of Fire About 75 per cent of active volcanoes
• Mediterranean belt Vesuvius, Etna, Stromboli, Santorini
• Ridge volcanism Iceland and the Azores
• Rift volcanism East African Rift
• Hotspots Hawaii, Yellowstone, Réunion
• Exam link UPSC Prelims, Geography: Geomorphic Processes and Landform Evolution

Where Does It Fit?

This topic follows the one on active, dormant and extinct volcanoes and maps where they occur. It is the volcanic counterpart of the distribution of earthquakes, and the two maps are closely related. Previous topic: Extinct, Dormant and Active Volcanoes. Next topic: Tsunami: Mechanism, Properties and Effects.

What Is the Ring of Fire?

In short: the Ring of Fire is a horseshoe-shaped belt around the Pacific Ocean with the most volcanoes and earthquakes on Earth.

The Circum-Pacific belt, popularly called the Ring of Fire, runs for about 40,000 km along the edges of the Pacific Ocean. It follows the subduction zones where the Pacific, Nazca, Cocos, Juan de Fuca and other plates dive beneath neighbouring plates. It has more than 450 volcanoes, which is about three-quarters of all active and dormant volcanoes, and about 90 per cent of the world’s earthquakes, including most of the largest. The belt runs from the Andes along the western coast of the Americas, through the Cascades and the Aleutians, down the coasts of Kamchatka, Japan, the Philippines, Indonesia and New Zealand, to the islands of the southwestern Pacific. The mechanism is explained in Plate Boundaries: Divergent, Convergent, Transform and Plate Boundaries: Divergent, Convergent, Transform.

Which Volcanoes Lie on the Pacific Ring of Fire?

The Ring of Fire follows the subduction zones around the Pacific plate, described in Plate Boundaries: Divergent, Convergent, Transform. Indonesia has the largest number of active volcanoes of any country.

What Is Mediterranean Volcanism?

The Mediterranean (or Alpine-Himalayan) belt is the second great volcanic zone. It lies where the African and Arabian plates collide with the Eurasian plate.

• Italy: Vesuvius, which buried Pompeii and Herculaneum in 79 CE, Mount Etna in Sicily, one of the most active volcanoes in Europe, and Stromboli, called the lighthouse of the Mediterranean, which erupts almost continuously.
• Greece and the Aegean: Santorini, whose giant eruption in the Bronze Age created a caldera, and Nisyros.
• Turkey, the Caucasus and Iran: Mount Ararat, Mount Elbrus and Mount Damavand, mostly dormant.
• Extension to the east: the belt runs through the Himalaya, where there are no active volcanoes, to the Indonesian arc, where it joins the Ring of Fire.

Where Else Do Volcanoes Occur?

• Mid-oceanic ridges: the Mid-Atlantic Ridge has Iceland, the Azores and Tristan da Cunha. Surtsey, a new island off Iceland, rose from the sea in 1963.
• Rift valleys: the East African Rift has Mount Kilimanjaro, Mount Kenya, Nyiragongo and Ol Doinyo Lengai, the only volcano that erupts carbonatite lava.
• Intraplate hotspots: Hawaii in the Pacific, Yellowstone in the USA, the Canary Islands and Réunion in the Indian Ocean, which is linked with the Deccan Traps.
• Back-arc and continental settings: small fields such as those of Central France and Eastern China.

The hotspots are explained in the context of mantle plumes and plate movement in Plate Tectonics: Major and Minor Lithospheric Plates. The comparable map of earthquakes is in Distribution of Earthquakes and Earthquake Observatories. As an analytical point, the world map of volcanoes is a map of plate boundaries, with a few exceptions over hotspots.

How Does the Distribution Link to Hazard and Benefit?

Living near a volcano brings both risk and reward. About 800 million people live within 100 km of an active volcano, drawn by fertile ash soils, geothermal power and tourism. The risks are ash falls that ground aircraft, mudflows called lahars, pyroclastic flows and, in coastal settings, tsunamis. Indonesia, the Philippines, Japan, Italy, Mexico and the Pacific coast of the United States have the largest exposed populations, and each runs monitoring observatories. Eruptions far from people can still matter, since a very large eruption can cool the global climate for a year or two by putting sulphur gases into the stratosphere. The idea that nearly all volcanoes lie on plate boundaries was one of the early supports for plate tectonics.

Why Is This Topic Important?

• Map Locations are asked
• Evidence Supports plate tectonics
• Hazard Risk zones

What Came Next?

The next topic explains the tsunami, which often follows an undersea earthquake or eruption. Next topic: Tsunami: Mechanism, Properties and Effects.

Key People and Terms

• Ring of Fire Belt around the Pacific
• Mediterranean belt Volcanoes along Africa-Eurasia collision
• Hotspot Fixed plume of hot mantle
• Rift volcanism Volcanoes in continental rifts
• Volcanic arc Chain at a subduction zone
• Carbonatite Rare carbonate-rich lava

Exam Corner

Mains Angle

Questions ask for the relation between volcano distribution and plate tectonics. These points add depth.

• Pattern Follows plate boundaries
• Exceptions Hotspots
• Comparison Volcano and earthquake maps