What is formed due to coral reefs building up around volcanic islands?

What is formed due to coral reefs building up around volcanic islands?

• A. Atolls
• B. Deep-ocean Trenches
• C. Seamounts
• D. Ocean Currents

Answer: (A)

Coral reefs form a unique geological structure known as atolls when they build up around volcanic islands. An atoll is a ring-shaped coral reef that encircles a lagoon, typically formed when the volcanic island gradually sinks over time. As the island subsides, coral growth persists at the surface, leading to the development of the atoll structure. This process begins with a volcanic island emerging from the ocean, which is then colonized by coral larvae that grow and expand over thousands of years. As the island erodes and sinks, the coral continues to thrive on the shallow waters surrounding it, forming a circular barrier that encloses a lagoon. The result is a distinct formation, characterized by its circular shape and the lagoon in the center. Other choices do not fit this description; deep-ocean trenches are formed by the subduction of tectonic plates, seamounts are underwater mountains typically not associated with coral growth, and ocean currents are movements of water that do not directly relate to the formation of coral structures. Hence, the formation of atolls around volcanic islands is clearly the result of coral reef development in response to geological changes in the surrounding environment.

Coral reefs form a unique geological structure known as atolls when they build up around volcanic islands. An atoll is a ring-shaped coral reef that encircles a lagoon, typically formed when the volcanic island gradually sinks over time. As the island subsides, coral growth persists at the surface, leading to the development of the atoll structure.

This process begins with a volcanic island emerging from the ocean, which is then colonized by coral larvae that grow and expand over thousands of years. As the island erodes and sinks, the coral continues to thrive on the shallow waters surrounding it, forming a circular barrier that encloses a lagoon. The result is a distinct formation, characterized by its circular shape and the lagoon in the center.

Other choices do not fit this description; deep-ocean trenches are formed by the subduction of tectonic plates, seamounts are underwater mountains typically not associated with coral growth, and ocean currents are movements of water that do not directly relate to the formation of coral structures. Hence, the formation of atolls around volcanic islands is clearly the result of coral reef development in response to geological changes in the surrounding environment.