Maarg Manthan · Topic 4.6

Hotspots, Mantle Plumes, Geysers and Hot Springs

Geography › Mountains, Volcanoes, Earthquakes and Tsunami · Topic 4.6

A hotspot is a fixed region of unusually high heat and volcanism, fed by a mantle plume, a column of hot rock rising from deep in the mantle. As a plate drifts over it, a chain of volcanoes forms, as in Hawaii. Geysers and hot springs are surface features where groundwater heated by volcanic or geothermal heat erupts or flows out, and they are sources of geothermal energy.

6 min read · UPSC Prelims · Geography · Mountains, Volcanoes, Earthquakes and Tsunami

At a Glance

Hotspot Fixed plume of hot mantle under a moving plate
Chain of volcanoes Oldest island is farthest from the hotspot
Examples Hawaii, Yellowstone, Reunion, Iceland
Geyser Hot spring that erupts water and steam
Indian hot springs Manikaran, Puga, Tatapani, Bakreshwar
Exam link UPSC Prelims, Geography: Mountains, Volcanoes, Earthquakes and Tsunami

Where Does It Fit?

This is the sixth topic of the category on mountains, volcanoes, earthquakes and tsunami. The previous topic described the styles of eruption at plate boundaries, and this one covers volcanism away from boundaries and its quieter surface forms. The next topic covers the distribution of volcanoes and earthquakes. Previous topic: Types of Volcanic Eruptions. Next topic: Distribution of Volcanoes and Earthquakes – Ring of Fire.

What Are Hotspots and Mantle Plumes?

In short: a hotspot is a fixed volcanic source in the mantle, over which a plate slides and leaves a trail of volcanoes.

Most volcanoes lie at plate boundaries, but some, such as those of Hawaii, lie in the middle of a plate. They are explained by hotspots. A mantle plume is a narrow column of unusually hot rock that rises from deep in the mantle, possibly from near the core-mantle boundary. When the plume reaches the base of the lithosphere, the pressure falls, the rock melts and magma erupts at the surface. The plume stays almost fixed, while the plate above moves, so the volcano is carried away from its source and goes extinct, and a new volcano forms over the hotspot. Over millions of years this makes a chain of volcanoes that grow older along the direction of plate motion. The plates are discussed in Plate Tectonics and Types of Plate Boundaries.

Which Are the Important Hotspots?

Hotspot	Location	Feature
Hawaii	Pacific plate	The Hawaiian Islands and the Emperor Seamount chain; Kilauea and Mauna Loa are active; the island of Hawaii is youngest and Kauai is older; a new seamount, Kamaʻehuakanaloa (Loihi), is growing offshore
Yellowstone	North American plate, USA	Supervolcano with geysers, a huge caldera and a track of older calderas along the Snake River Plain
Reunion	Indian Ocean	Linked to the Deccan Traps; the track runs through Chagos, Maldives and Mascarene islands
Iceland	Mid-Atlantic Ridge	A hotspot on a ridge, which raised the island above the sea
Others	Tristan da Cunha, Galapagos, Afar, Canary Islands	Plume-related volcanic islands and regions

The bend in the Hawaii-Emperor chain, about 47 million years ago, shows a change in the direction of movement of the Pacific plate. The Reunion plume produced the Deccan Traps, as in Movement of the Indian Plate. As an analytical point, the hotspot model explains the age progression in island chains well, but the depth of origin of plumes is still debated among geologists, so the idea of fixed, deep plumes is a working model, not a settled fact.

What Are Geysers?

A geyser is a hot spring that erupts periodically, shooting a column of hot water and steam into the air. Geysers need three things: a source of heat, plenty of water, and a plumbing system of narrow channels with constrictions that trap the water. Water at depth is heated above the normal boiling point because of the pressure; when it rises and the pressure falls, it flashes to steam and expels the water above it. The process repeats as the system refills. Geysers are rare and occur in only a few places: Yellowstone in the United States, which has over half of the world’s geysers, including Old Faithful, which erupts about every 90 minutes or so; Iceland, where the word geyser comes from the Geysir; Kamchatka in Russia; El Tatio in Chile; and New Zealand. Many geysers are in volcanic regions, along plate boundaries or over hotspots.

What Are Hot Springs and Where Are They Found in India?

A hot spring is a spring where groundwater, heated by contact with hot rock or magma, flows out at the surface at a temperature above the surroundings, without erupting. Fumaroles are vents that release gas and steam, and mud pots form where acidic gases dissolve rock to clay. India has several hundred thermal springs grouped by the Geological Survey of India into geothermal provinces, mostly along the Himalayas, along the Narmada-Son-Tapi rift valleys, in the west coast and in the Godavari valley.

Region	Examples
Himalayas	Manikaran (Himachal Pradesh), Tapovan and Yamunotri (Uttarakhand), Puga and Chumathang (Ladakh), Yumthang (Sikkim)
Rift valleys of central India	Tatapani (Chhattisgarh), Anhoni and Salbardi (Narmada-Son region)
Eastern and western India	Bakreshwar (West Bengal), Rajgir (Bihar), Unkeshwar and Vajreshwari (Maharashtra)

The Puga Valley in Ladakh is among the most promising sites for geothermal energy in India, and pilot projects have been planned there. The natural heat of the Earth, used as geothermal energy, can give steady power, heating and bathing resources, and it is among the clean sources of power discussed in Energy and Biotic Resources of the Oceans in the context of marine renewables.

Why Is This Topic Important?

Hotspots Explain volcanoes away from boundaries
India Reunion and the Deccan; hot springs
Energy Geothermal potential

What Came Next?

The next topic describes the distribution of volcanoes and earthquakes and the Ring of Fire. Next topic: Distribution of Volcanoes and Earthquakes – Ring of Fire.

Key People and Terms

Hotspot Fixed volcanic source in the mantle
Mantle plume Rising column of hot rock
Geyser Erupting hot spring
Fumarole Steam and gas vent
Geothermal energy Heat from inside the Earth
Seamount Submerged volcano

Exam Corner

Points to Remember

Hotspots are fixed; plates move.
Old Faithful is in Yellowstone.
The Reunion hotspot made the Deccan Traps.
Puga Valley in Ladakh is a geothermal prospect.
Island chains get older away from the hotspot.

Do Not Confuse With

Geyser and hot spring Erupts periodically versus flows steadily
Hotspot and plate boundary volcano Inside a plate versus at an edge
Mantle plume and magma chamber Deep source versus shallow store

Memory Hook

Plume stands still, plate slides on; islands age along the track.

Mains Angle

Questions ask how volcanoes arise inside plates. These points add depth.

Model Fixed plume and moving plate
India Reunion and the Deccan Traps
Energy Geothermal potential

A Question You May Face

An original practice question, not a past paper question.

“Explain the hotspot theory of volcanism and discuss the potential of geothermal energy in India.”

How to Answer

Theory Plume and plate motion.
Evidence Hawaii chain.
India Reunion and hot springs.
Energy Puga and others.

GS Relevance

Prelims: hotspots, geysers, hot springs of India. GS Paper 1: volcanism; GS Paper 3: geothermal energy.

Frequently Asked Questions

What is a hotspot?

A hotspot is a fixed area of intense volcanic activity fed by a mantle plume, a column of hot rock rising from deep in the mantle. As a plate moves over it, a chain of volcanoes forms that grows older in the direction of plate motion, as in the Hawaiian Islands.

How did the Hawaiian Islands form?

The Hawaiian Islands formed as the Pacific plate moved northwest over a fixed hotspot. Each volcano forms over the hotspot and is carried away, so the island of Hawaii is the youngest and still active, while the islands to the northwest, such as Kauai, are older.

What is a geyser?

A geyser is a hot spring that periodically erupts a column of hot water and steam. It needs heat, water and a narrow plumbing system. Famous geysers include Old Faithful in Yellowstone, the Geysir in Iceland and those of El Tatio in Chile.

Where are the hot springs of India?

India's hot springs are found mainly along the Himalayas, such as Manikaran, Tapovan and Puga, along the Narmada-Son rift valleys, as at Tatapani, and on the west coast and in parts of eastern India, such as Bakreshwar and Rajgir.

What is the geothermal potential of India?

India has several hundred thermal springs grouped into geothermal provinces by the Geological Survey of India. The Puga Valley in Ladakh is considered among the best sites for geothermal power, though development in India is still at a pilot stage.

PYQ Practice — Statement Analysis

1 The Hawaiian Islands are formed by a hotspot.

True

The Pacific plate moves over a fixed plume.

2 In a hotspot island chain, the oldest island is nearest the hotspot.

False

The youngest island is nearest the hotspot.

3 The Reunion hotspot is linked with the Deccan Traps.