• 10 parts
  • Checked October 2026

Coral Reef Diagram Labeled: Zones and Kinds of Reef

Name a reef's zones from lagoon to drop-off, then tell a fringing reef, a barrier reef and an atoll apart.

Coral Reef Diagram Labeled: Zones and Kinds of Reef

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1 2 3 4 5 6 7 8 9 10
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Write the name of each numbered part.Answer key

  1. Reef crest
  2. Lagoon
  3. Fore reef
  4. Reef flat
  5. Drop-off
  6. Patch reef
  7. Fringing reef
  8. Barrier reef
  9. Atoll
  10. Volcanic island

Drawn for this site on 2026-10-03 from plain geometry. Licence: own work.

Each numbered ring is a button. Use the arrow keys to move between them and Enter to choose. Names are read out in Study, and once a part is answered.

Next step Next: the zones of the ocean

All 10 parts on the diagram

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Across a reef 6

  1. Reef crest The highest part of the reef, where the waves break. It is almost always uncovered at low tide.
  2. Lagoon Sheltered water between the shore and the reef.
  3. Fore reef The seaward slope, running down into deeper water. It takes the force of the incoming waves.
  4. Reef flat The shallow, sheltered side behind the reef crest. Its floor is coral rock and loose sand.
  5. Drop-off The steep fall of the reef into deep water.
  6. Patch reef A small reef standing alone inside a lagoon.

Kinds of reef 4

  1. Fringing reef A reef that grows directly from the shore. It is the most common kind.
  2. Barrier reef A reef parted from the shore by a lagoon.
  3. Atoll A ring of reef around a lagoon, with no island inside.
  4. Volcanic island The island a fringing reef first grows around. When it sinks below the sea, the reef left behind is an atoll.

How this list was compiled: Every name checked on 2026-10-03 in at least two of these, counting the two NOAA pages as one source. (1) NOAA National Ocean Service, Corals tutorial, How do coral reefs form?, https://oceanservice.noaa.gov/education/tutorial_corals/coral04_reefs.html (fringing reefs, barrier reefs and atolls; the lagoon; the volcanic island that sinks; fringing reefs the most common). (2) The same tutorial, Coral reef zones, https://oceanservice.noaa.gov/education/tutorial_corals/media/supp_coral04b.html (reef flat, reef crest or algal ridge, forereef or reef front, the dropoff). (3) Wikipedia, Coral reef, sections Types and Zones, https://en.wikipedia.org/wiki/Coral_reef (fore reef, reef crest, back reef, reef flat, reef drop-off, reef lagoon, patch reef; the three classical kinds of reef). (4) Rützler and Macintyre, The Atlantic Barrier Reef Ecosystem at Carrie Bow Cay, Belize, Smithsonian Contributions to the Marine Sciences 12 (1982), read on the Internet Archive, https://archive.org/details/smithsoniancont121982smit (a measured barrier reef in five units: lagoon, back reef, reef crest, inner fore reef, outer fore reef; patch reefs in the lagoon; the reef flat; the reef drop-off). Licence: own work

The drawing: Drawn for this site on 2026-10-03 from plain geometry. Own original drawing; nothing is traced or copied. Licence: own work

How it works

This coral reef diagram is labeled in two drawings. The first cuts across a reef from an island's beach to deep water. The second shows a fringing reef, a barrier reef and an atoll from above.

Read the full guide

Across a reef

Start at the island. The lagoon is the calm water behind the reef, and a patch reef stands alone in it. The reef flat is the shallow shelf on the sheltered side. Waves break on the reef crest, the highest part. Past it the fore reef slopes down to the drop-off.

Kinds of reef

A fringing reef grows directly from the shore. A barrier reef lies farther out, with a lagoon between it and the land. An atoll is a ring of reef around a lagoon, left when a volcanic island sinks below the sea.

  • Some books call the sheltered side behind the crest the back reef. The quiz takes that name for the reef flat and the lagoon.

Questions and answers

What are the zones of a coral reef?

Moving seaward from the shore, NOAA lists the reef flat, the reef crest and the fore reef. A barrier reef also has a lagoon behind it, and the fore reef can end in a steep drop-off.

What are the three types of coral reefs?

Fringing reefs, barrier reefs and atolls. A fringing reef grows directly from the shore, a barrier reef is separated from the land by a lagoon, and an atoll is a ring of reef around a central lagoon.

What is the difference between a fringing reef and a barrier reef?

Both border a shoreline. A fringing reef projects seaward directly from the shore. A barrier reef lies at a greater distance, with a lagoon of open, often deep water between it and the land.

How does an atoll form?

A fringing reef forms around a volcanic island. If the island sinks completely below sea level while the coral keeps growing upward, a ring of reef is left around a central lagoon. That ring is an atoll.

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