2.5.2

Types of Reefs

Test yourself

Types of Coral Reef

There are three types of coral reef: fringing, barrier and atoll reefs.

Illustrative background for Fringing reefsIllustrative background for Fringing reefs ?? "content

Fringing reefs

  • These grow from a shore/coastline or are adjacent to (next to) one.
  • They are very sensitive to human activity.
  • The Bahamas has one of the world’s most extensive coral reef systems with lots of fringing reefs.
Illustrative background for Barrier reefsIllustrative background for Barrier reefs ?? "content

Barrier reefs

  • Barrier reefs are linear reefs (generally parallel to a shore).
  • They are separated from the shore by a lagoon
  • The Great Barrier Reef in Queensland, North East Australia is the world’s largest coral reef system and an example of a barrier reef.
  • Barrier reefs are sensitive to human activity
Illustrative background for Atoll reefsIllustrative background for Atoll reefs ?? "content

Atoll reefs

  • Atoll reefs are often circular.
  • They surround deep lagoons.
  • They are found mid-ocean.
  • Most of the world’s atolls are found in:
    • The Pacific Ocean: for example, Funafuti. Funafuti is a small coral atoll that’s only 20 meters (66 ft) wide at the narrowest parts, and about 400 meters (1300 ft) at the widest part of the island.
    • The Indian Ocean: for example, The Maldives. The Maldives is made up of about 1,200 tiny coral islands grouped into 26 atolls.
Illustrative background for How do atoll reefs form?Illustrative background for How do atoll reefs form? ?? "content

How do atoll reefs form?

  • Corals start to grow around a volcanic island, which forms a fringing reef.
  • The reef continues to expand over hundreds of thousands of years.
  • As the reef expands, the interior island starts to subside.
  • The fringing reef becomes a barrier reef.
  • Eventually, the island will completely subside beneath the water.
  • This leaves a ring of coral with a lagoon in the centre (atoll reef).

Jump to other topics

1Paper 1 - Changing River Environnments

2Paper 1 - Changing Coastal Environments

3Paper 1 - Changing Ecosystems

4Paper 1 - Tectonic Hazards

5Paper 1 - Climate Change

6Paper 2 - Changing Populations

7Paper 2 - Changing Towns & Cities

8Paper 2 - Development

9Paper 2 - Changing Economies

10Paper 2 - Resource Provision

Unlock your full potential with Seneca Premium

  • Unlimited access to 10,000+ open-ended exam questions

  • Mini-mock exams based on your study history

  • Unlock 800+ premium courses & e-books

Get started with Seneca Premium