Top 10 Interesting and Fun Facts About Oceans and Islands

Updated on January 18, 2019
stuff4kids profile image

Amanda is a retired educator with many years of experience teaching children of all ages and abilities in a wide range of contexts.

The oceans cover most of the planet and are scattered with thousands of islands
The oceans cover most of the planet and are scattered with thousands of islands | Source

1. How the Oceans Were Formed

The oceans began to form many millions of years ago when the earth was still cooling and solidifying following its early molten, liquid state. The early oceans came about as a consequence of volcanic activity. We can define three clear stages in the formation of the oceans on the early Earth.

  1. As the young Earth cooled, volcanoes erupted, throwing out a mixture of gases that formed the early atmosphere
  2. When the atmosphere was saturated with water vapor, the vapor condensed, falling as rain. Rainwater began to collect in vast hollows
  3. The earth cooled and volcanic eruptions became fewer. For the last 100 million years the volume of water in the seas has stayed about the same

2. What Are Ocean Currents?

The map below shows the main ocean currents. Ocean currents are the directions of water flow around the world's seas. Currents are caused by the wind, by the spin of the earth, and by colder water sinking under warmer water.

A map showing the ocean currents
A map showing the ocean currents | Source

3. Ocean Waves

Most waves are caused by wind blowing across the surface of the sea. The height and power of the waves depends on the speed of the wind and how far it has blown. Water in a wave appears to be moving forward, but in fact it is the kinetic energy which moves through the water, and the water itself rolls in circles.

What is a Wave?

Waves have two distinct phases called crests and troughs. As water circles upward it reaches the crest and as it rolls back down it forms the trough. At the shoreline, the base of a wave is held back and the water moves faster, toppling over as it reaches the land, causing "breakers".

Force of the Waves

When waves break on the shore, they exert a tremendous force. The weight of the sea hitting land can create pressures of more than 25 tonnes per square metre. That's 30 times as great as the pressure exerted on land by the average human foot.

What Causes Whirlpools?

Whirlpools are caused by a clash of tidal flows in a place where the sea floor is uneven. Currents rush toward each other, and, if they hit a rocky shelf on the sea floor, water surges upward, turning the surface into a seething mass.

A photograph of the Naruto ocean whirlpool taken from a boat
A photograph of the Naruto ocean whirlpool taken from a boat | Source

4. Ocean Data and Facts

What?
How Much?
Total surface area
362 million square km (139.8 million square miles)
Total volume
1.35 billion cubic km (324 million cubic miles)
Mean (average) depth
3.5 km (2.2 miles)
Weight of water
1.32 x 10^18 tonnes
% of Earth's water
94%
Temperature range
-1.9 to 36 degrees Celsius (28 to 97 degrees Fahrenheit)
Freezing temperature of sea water
-1.9 degrees Celsius (28 degrees Fahrenheit)
Deepest known point
10,920 m (35,827 feet)
Table showing important ocean data metrics
  • More than 60% of the earth's surface is covered by water deeper than 1.6 km (1 mile)
  • The average depth of the Pacific Ocean is 3.94 km (2.4 miles) and the average depth of the Atlantic Ocean is 3.57 km (2.2 miles)
  • There's more gold dissolved in sea water than there is on land. The concentration is 0.000004 parts per million
  • The ocean current called the Gulf Stream contains about 100 times as much water as the combined volume of all the rivers in the world

5. Minerals in the Oceans

Minerals dissolved from rocks by rivers are washed into the oceans. The most abundant are sodium and chlorine, which together form salt. The average salinity (saltiness) of the ocean is 33 to 38 parts salt per 1,000 parts water.

The ocean also contains:

  • sulphate (7.94%)
  • magnesium (3.66%)
  • calcium (1.19%)
  • and potassium (1.13%)

The total amount of salt in the world's oceans and seas would cover the entire continent of Europe to a depth of 5 km (3 miles).

Sea salt crystallizing on rocks at the edge of the Dead Sea
Sea salt crystallizing on rocks at the edge of the Dead Sea | Source

6. What Are Islands?

Islands are areas of land, smaller than continents, surrounded by water. They are found in seas, rivers, and lakes. Islands range in size from small mud and sand islands measuring only a few square metres to the largest, Greenland, which measures more than 2 million square km.

7. What Are the Four Types of Island?

Scientists define four main types of islands:

  1. Coral islands
  2. Volcanic islands
  3. Islands formed by a change in sea level
  4. Island arcs

Let's look at each in turn.

Coral Islands

A coral island forms when corals (tiny marine organisms) grow up toward the surface of the ocean from an underwater platform in shallow water, such as the peak of a seamount. The coral skeletons build up over many years until they reach the surface.

Malé, capital of Maldives, is now completely built over. The Maldives are all coral islands
Malé, capital of Maldives, is now completely built over. The Maldives are all coral islands | Source

Volcanic Islands

Volcanoes that erupt beneath the ocean may eventually grow to reach the surface, where they emerge as islands. Volcanic islands often form close to tectonic plate boundaries.


The volcanic island of Surtsey appeared south of Iceland in the Atlantic Ocean as recently as 1963
The volcanic island of Surtsey appeared south of Iceland in the Atlantic Ocean as recently as 1963 | Source

Islands Formed By Changes in Sea Level

A rise in sea level, for example at the end of an ice age, may cut off an area of land from a continent, forming an island. Great Britain was formed in this way. Some pieces of land become islands temporarily during a high tide.

Mont Saint-Michel lies off the north-west coast of France. It is accessible by land at low tide but becomes an island when the sea comes in at high tide
Mont Saint-Michel lies off the north-west coast of France. It is accessible by land at low tide but becomes an island when the sea comes in at high tide | Source

An Island Arc

An island arc is a chain of volcanic islands that usually forms close to a subduction zone. Some island arcs contain many thousands of islands. The Japanese islands were formed in this way.

The Ryuku islands between Japan and Taiwan are a typical island arc formation arising along the line of a subduction zone
The Ryuku islands between Japan and Taiwan are a typical island arc formation arising along the line of a subduction zone | Source

8. The World's Largest Islands

Name of Island
Ocean Location
Area in square km (square miles)
Greenland
Arctic Ocean
2,175,219 (839,852)
New Guinea
Western Pacific Ocean
792,493 (305,981)
Borneo
Indian Ocean
725,416 (280,083)
Madagascar
Indian Ocean
587,009 (226,644)
Baffin Island
Arctic Ocean
507,423 (195,916)
Honshu
North West Pacific
227,401 (87,799)
Great Britain
North Atlantic
218,065 (84,195)
Victoria Island
Arctic Ocean
217,278 (83,891)
Ellesmere Island
Arctic Ocean
196,225 (75,762)
Table showing the ocean locations and area sizes of the world's largest islands

9. How Coral Atolls Are Formed

An atoll is a ring-shaped coral island with a lagoon in its center. Atolls form when a coral reef builds up around a volcanic island, and the island subsequently sinks below sea level. As the island sinks, the coral continues to grow.

The illustration below shows the four stages of the formation of a coral atoll:

  1. A coral reef builds up, fringing a volcanic island
  2. As the island starts to sink, the coral continues to grow upward
  3. The island sinks further, coral forms around the beginnings of a lagoon
  4. The island disappears completely, leaving a coral atoll

An illustration showing the formation of a coral atoll
An illustration showing the formation of a coral atoll | Source

10. Record-Breaking Oceans and Islands

  • The greatest ocean current is the Antarctic Circumpolar Current (also known as the West Wind Drift Current), which flows at a rate of 130,000,000cu m (4.3 billion cu feet) per second
  • The highest recorded wave (excluding seismic sea waves) was 34 m (112 feet) from trough to crest. It was recorded in 1933 en route from the Philippines to the USA
  • The world's remotest island is Bouvet Island, about 1,700 km (1,056 miles) from the nearest land, Queen Maud Land on the coast of Eastern Antarctica
  • The world's largest coral atoll is Kwajalein in the Marshall Islands, in the central Pacific Ocean. Its reef is 283 km (176 miles) long, and encloses a lagoon of 2,850 square km (1,100 square miles)

Bouvet Island is the world's remotest island
Bouvet Island is the world's remotest island | Source

A Last Word

So, we've come to the end of our journey through the world's oceans and islands. I hope you've enjoyed reading these top 10 interesting and fun facts. I also hope you've learned something new. Scientists, both women and men, work hard every day throughout the world to discover more about our unique and beautiful world. And there's always something new to find out. Perhaps you'll be inspired to become a scientist, too, and help explore and protect our extraordinary planet.

© 2019 Amanda Littlejohn

Comments

Submit a Comment
  • stuff4kids profile imageAUTHOR

    Amanda Littlejohn 

    3 weeks ago

    Hi Zia,

    Thanks for reading and for your kind comments. Islands are fascinating, aren't they? And thank you for your great contribution. I had no idea people actually lived on Bouvet Island. How extraordinary! I wonder how on earth they survive?

  • aziza786 profile image

    Zia Uddin 

    3 weeks ago from Birmingham

    Another fascinating article. At least I know Britain was formed by sea level changes. I was fascinated by Bouvet Island as the most remotest island in the world. I googled it and found that there is a small population of less than 300 people living there. Cheers.

  • stuff4kids profile imageAUTHOR

    Amanda Littlejohn 

    4 weeks ago

    Hi Shelley,

    Thanks for your comment. You're right to point out that we have way too much garbage. And one of the greatest environmental threats is the problem of particles of plastic (and islands of it) contaminating not only the oceans themselves, but the fish which live in them. And which we then eat.

  • FlourishAnyway profile image

    FlourishAnyway 

    4 weeks ago from USA

    I enjoyed this and learned a lot too. I didn’t know there were different types of islands. And all that salt! Too bad we can’t figure out a natural way to use salt to degrade garbage. We have a lot of both.

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