From which language does the word atoll come?

Dhivehi, spoken in the Maldives

What is a faro in the Maldives?

A small ring-shaped reef inside an atoll

Why do atoll nations worry about climate change?

Rising seas threaten low islands

Atoll Formation Quiz: Darwin's Theory and the Maldives Reefs

This atoll formation quiz dives into how rings of coral islands grow in the open ocean. Play 10 interactive questions on Charles Darwin's 1842 subsidence theory, fringing and barrier reefs, the drilling at Enewetak that proved him right, the Maldivian origin of the word atoll, lagoons and faros, low island heights and how rising seas affect coral nations.

Start Atoll Formation Quiz

🎯 Daily Trivia Challenge • 🧠 10 Questions • ⏱️ 150 Seconds

Question 1 / 10 Time: 150s

Scientist
Who proposed the classic theory of atoll formation?
Base
What do most atolls sit on?
First
Which reef type forms first around a young island?
Second
Which reef forms as the island sinks and a lagoon opens?
Last
What is left when the volcano disappears below sea level?
Proof
Where did drilling in the 1950s hit volcanic rock below an atoll?
Word
From which language does the word atoll come?
Faro
What is a faro in the Maldives?
Height
About how high is the Maldives' highest natural ground?
Risk
Why do atoll nations worry about climate change?

Explanations: answer key for all 10 questions

Q1: Who proposed the classic theory of atoll formation?
Answer: Charles Darwin
He wrote about coral reefs in 1842.
Q2: What do most atolls sit on?
Answer: A sunken volcano
Coral grows on its slopes.
Q3: Which reef type forms first around a young island?
Answer: A fringing reef
It hugs the shoreline.
Q4: Which reef forms as the island sinks and a lagoon opens?
Answer: A barrier reef
Water separates it from land.
Q5: What is left when the volcano disappears below sea level?
Answer: A ring reef around a lagoon
Coral keeps growing upward.
Q6: Where did drilling in the 1950s hit volcanic rock below an atoll?
Answer: Enewetak
It reached basalt beneath more than 1,200 m of reef.
Q7: From which language does the word atoll come?
Answer: Dhivehi, spoken in the Maldives
The Maldivian word is atholhu.
Q8: What is a faro in the Maldives?
Answer: A small ring-shaped reef inside an atoll
It is another Dhivehi word.
Q9: About how high is the Maldives' highest natural ground?
Answer: About 2.4 m
It is one of the world's lowest countries.
Q10: Why do atoll nations worry about climate change?
Answer: Rising seas threaten low islands
Warming water also bleaches coral.

Darwin's Sinking Volcano Idea

Charles Darwin saw coral reefs during the Beagle voyage and in 1842 published his subsidence theory. A fringing reef first grows around a volcanic island. As the volcano slowly sinks, coral keeps building upward, a lagoon opens and the reef becomes a barrier reef. When the peak vanishes, a ring of reef around a lagoon remains, an atoll.

The idea was confirmed in the early 1950s when drilling at Enewetak in the Marshall Islands passed through more than 1,200 m of reef limestone before hitting volcanic basalt. Changing sea levels during ice ages also shaped atoll shapes and sandy islets.

The word atoll comes from the Maldivian Dhivehi word atholhu, and the Maldives has 26 natural atolls, with ring-shaped faros inside some of them. Its highest natural ground is only about 2.4 m above sea level, so rising seas and coral bleaching are urgent concerns.

What This Quiz Teaches

Ocean and earth science fans will enjoy these questions.

What Darwin proposed
How reef types change
What drilling proved
Where the word comes from
Why atolls face risks

Did You Know?

Atoll islets are made of coral sand.
Lagoons can be very deep.
Kiribati and Tuvalu are atoll nations.
Reef growth can match slow sinking.
Storms build and move islets.