How are atolls formed for kids?

How are atolls formed for kids?

An atoll is a ring of coral around a shallow body of water called a lagoon. Atolls form when corals build a colony, or reef, around the top of a volcanic island. Eventually, the reef reaches the surface of the water and becomes land. The volcanic island may sink, leaving a lagoon in its place.

How does an island become an atoll?

As the reef expands, the interior island usually begins to subside and the fringing reef turns into a barrier reef. When the island completely subsides beneath the water leaving a ring of growing coral with an open lagoon in its center, it is called an atoll.

Who explained how atolls are formed?

Darwin also proposed a theory of how isolated rings of coral reefs, known as atolls, formed. He suggested that they originally grew around extinct volcanoes which then sank into the sea, leaving the reef as an isolated circle.

What are the four stages of forming an atoll?

Terms in this set (4) Oceanic volcano forms and emerges from the sea surface- forms an island and becomes colonized by reef-building corals. Forms a fringing barrier reef around the island, island begins to sink. Island continues to sink, a barrier reef is formed with a lagoon between the reef and island.

Why do atolls form?

The formation of an atoll is a slow process that can take millions of years. It begins when an underwater volcano erupts, creating a buildup of lava on the seafloor. With continued eruptions, the lava continues to build until it breaks through the ocean’s surface and forms an island.

What is subsidence theory?

Definition. The subsidence hypothesis of coral reef development was proposed by Charles Darwin and was formulated during his voyage on the Beagle. It envisaged that fringing reefs, barrier reefs, and atolls represent successive stages in an evolutionary sequence.

What is atoll stage?

Atoll: Circular reef remaining after a volcanic island has completely eroded beneath the sea. Subaerial stage: The above ground stage in the formation of a volcano. Submarine stage: The underwater stage in the formation of a volcano.

How does the formation of an atoll relate to plate tectonics?

The original understanding of atoll formation is attributed to Charles Darwin, who reasoned that atolls are remnants of fringing reefs that once grew around islands; over time, these islands eroded away and/or sank (Darwin didn’t know this, but islands sink as the tectonic plates on which they ride cool and contract …

How are barrier reefs formed?

Coral reefs begin to form when free-swimming coral larvae attach to submerged rocks or other hard surfaces along the edges of islands or continents. As the corals grow and expand, reefs take on one of three major characteristic structures — fringing, barrier or atoll.

Is Tahiti an atoll?

Among its 118 islands and atolls, 67 are inhabited. Tahiti, which is in the Society Islands group, is the most populous island, being home to nearly 69% of the population of French Polynesia as of 2017….Geography.

What is the difference between an island and an atoll?

is that atoll is a type of island consisting of a ribbon reef that nearly or entirely surrounds a lagoon and supports, in most cases, one to many islets on the reef platform atolls have a unique geology, so not all islands with a reef and a lagoon are atolls while island is a contiguous area of land, smaller than a continent, totally surrounded by

How does an atoll originally form?

Atolls, which are circular islands or archipelagos located around a central lagoon, are formed when the soft stone of a volcanic island is worn away, leaving behind only the coral reef that formed at its outskirts. Many Micronesian islands are atolls.

What are atolls usually located around?

An atoll is a ring-shape coral reef that is usually located around extinct volcanoes that have been partially submerged in seawater. Beside extinct volcanoes, atolls are around found around sea mountains. The Pacific and the Indian ocean contain most of the atolls in the world.

How are atolls and barrier reefs formed?

Types of Coral Reef Formations Fringing reefs. They are separated from the shore by narrow, shallow lagoons. Barrier reefs. At their shallowest point, they can reach the water’s surface forming a “barrier” to navigation. Atolls.