Understanding Island Origins

Islands are pieces of land surrounded by water, but they can form in several different ways. Their origin tells us a lot about the geological processes that created them. Some islands are formed by volcanic activity, others are remnants of submerged continents, and some are built by living organisms like corals.

Analyzing the Options for Island Origin

Let's examine each of the given options to determine their geological origin:

• Reunion Island: This island is located in the Indian Ocean and is known for its active shield volcano, Piton de la Fournaise. Reunion Island is a classic example of an island formed by volcanic activity over a hotspot in the Earth's mantle.
• Andaman & Nicobar Islands: This archipelago in the Bay of Bengal is part of a mountain range that extends from the Himalayas and dips under the sea. Their origin is primarily related to the collision of tectonic plates, forming an island arc. While there is some volcanic activity (like Barren Island), the archipelago's main formation is tectonic/continental arc related, not purely from a single volcanic hotspot like Reunion.
• Lakshadweep Islands: These islands are a group of atolls and reefs in the Arabian Sea. They are formed on submerged volcanic structures but the landmass itself is built up from coral polyps and associated marine life. Therefore, they are considered coral islands or atolls.
• Maldives: Similar to Lakshadweep, the Maldives are an archipelago of coral atolls located in the Indian Ocean. The islands are low-lying and composed of coral debris and sand, built upon underlying volcanic ridges. Their visible landmass is a result of coral growth.

Identifying the Volcanic Island

Based on the analysis of each option's origin:

• Reunion Island is formed directly by volcanic eruptions from a hotspot.
• Andaman & Nicobar Islands are part of an island arc formed by plate tectonics, with some associated volcanic activity.
• Lakshadweep islands are coral atolls built on submerged features.
• Maldives are coral atolls built on submerged features.

The question asks for an island of volcanic origin. While some islands might have underlying volcanic bases or associated volcanic activity, Reunion Island is predominantly and directly a product of volcanic activity forming the landmass above sea level from a persistent hotspot.

Conclusion

Comparing the origins, Reunion Island is the clearest example among the options of an island primarily formed by volcanic processes.

Revision Table: Island Origins Summary

Additional Information: Types of Islands

Islands can be classified based on how they were formed:

• Continental Islands: These were once part of a continent but separated due to changes in sea level or geological activity. Greenland and Madagascar are examples.
• Oceanic Islands: These rise from the ocean floor and were never connected to a continent. They are often volcanic in origin.
  • Volcanic Islands: Formed by volcanic eruptions on the ocean floor that eventually rise above sea level. Examples include Hawaii, Iceland, and Reunion.
  • Coral Islands: Low-lying islands formed by the buildup of coral reefs. Atolls are a type of coral island forming a ring around a lagoon. Examples include the Maldives and Lakshadweep.
• Barrier Islands: Long, narrow islands parallel to the coastline, formed by the accumulation of sand.

Understanding the geological processes helps explain the unique characteristics of different island types.