Atolls

Atolls are ring-shaped coral reefs, islands, or series of islets. They are formed from the growth of coral reefs around the rim of a submerged volcanic island. Over time, the island erodes and sinks below sea level, leaving a ring of coral that continues to grow upwards. Atolls are typically found in warm ocean waters and are often associated with tropical and subtropical regions.

Formation

The formation of atolls begins with a volcanic island. As the island subsides, coral reefs grow around its edges. This process can be divided into three main stages:

1. Fringing Reef: Coral reefs grow around the edges of a volcanic island.
2. Barrier Reef: As the island begins to sink, the coral continues to grow upwards, forming a barrier reef separated from the island by a lagoon.
3. Atoll: Eventually, the island sinks completely below sea level, leaving a ring of coral with a central lagoon.

Geography

Atolls are typically found in the Pacific Ocean, Indian Ocean, and parts of the Caribbean Sea. They are often characterized by their unique ring shape and central lagoon. Some well-known atolls include the Maldives, the Marshall Islands, and the Chagos Archipelago.

Ecology

Atolls support a diverse range of marine life due to their complex structure and nutrient-rich waters. They provide habitats for various species of coral, fish, mollusks, and other marine organisms. The lagoons within atolls are often nurseries for juvenile fish and other marine species.

Human Settlement

Many atolls are sparsely populated due to their remote locations and limited resources. However, some atolls, such as those in the Maldives and the Marshall Islands, have significant human populations. These communities often rely on fishing, tourism, and limited agriculture for their livelihoods.

Threats

Atolls face several environmental threats, including climate change, sea level rise, and coral bleaching. Rising sea levels can submerge atolls, while increased ocean temperatures can lead to coral bleaching and the death of coral reefs. Human activities, such as overfishing and pollution, also pose significant threats to atoll ecosystems.

Related Pages

• Coral reef
• Lagoon
• Volcanic island
• Maldives
• Marshall Islands
• Chagos Archipelago